JPH10200147A - Photovoltaic element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance machinability and reliability wile increasing light absorption of a semiconductor layer by employing polycrystalline thin film, where polycrystalline grains having an irregular surface are mixed with polycrystalline grains having a flat surface, on the surface of a polycrystalline thin film. SOLUTION: A transparent conductive layer 103 is disposed between a polycrystalline thin film 102 and a semiconductor layer 104 in the case of a photovoltaic element where the light impinges on the side opposite to a substrate 101 but disposed between a rear metal reflection layer 102 and the semiconductor layer 104 in the case of a photovolaic element where the light impinges on the substrate 101 side. The transparent conductive layer 103 may have a flat surface but when level differences, protrusions or recesses are formed depending on the polycrystalline grain boundary of the polycrystalline thin film 102, adhesion between the transparent conductive layer 103 and the semiconductor layer 104 is enhanced and the degree of freedom and the controllability of the fabrication process of photovoltaic element are enhanced furthermore. Since scattering of light is accelerated on the interface between the transparent conductive layer 103 and the semiconductor layer 104, short circuit current is increased furthermore.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device.
More specifically, the present invention relates to a photovoltaic element having improved reliability such as yield, weather resistance and durability in a manufacturing process while improving photoelectric conversion efficiency by a light confinement effect.

[0002]

2. Description of the Related Art A photovoltaic element, which is a photoelectric conversion element for converting sunlight into electric energy, is widely applied as a small power source for consumer use such as a calculator and a wristwatch. It is attracting attention as a technology that can be put to practical use as so-called fossil fuel alternative power. A photovoltaic element is a technology that uses the photovoltaic power of a pn junction of a semiconductor. A semiconductor such as silicon absorbs sunlight to generate photocarriers of electrons and holes, and the photocarriers are formed inside the pn junction. It drifts due to the electric field and is taken out.

Heretofore, the most commonly used photovoltaic elements have used single crystal silicon as a material. Such a method of manufacturing a photovoltaic element is usually performed by using a semiconductor process. Specifically, C
A single crystal of silicon whose valence is controlled to be p-type or n-type is produced by a crystal growth method such as the Z method, and the single crystal is sliced to produce a silicon wafer having a thickness of about 300 μm. Further, a pn junction is formed by forming a layer of a different conductivity type by an appropriate means such as diffusion of a valence electron controlling agent so as to have a conductivity type opposite to the conductivity type of the wafer.

[0004] By the way, such photovoltaic devices using single crystal silicon have high production costs due to the high cost of manufacturing a silicon wafer and the high cost of a manufacturing process due to the use of a semiconductor process. Therefore, the production cost per unit power generation is higher than the existing power generation method, and it is considered that it is difficult to reduce this to a level that can be used for electric power.

Therefore, in promoting the practical use of photovoltaic elements as power, it has been recognized that cost reduction and large area are important technical issues.
There has been a search for materials with high conversion efficiencies.

[0006] Materials for such a photovoltaic element include:
A tetrahedral amorphous semiconductor or polycrystalline semiconductor such as amorphous silicon, amorphous silicon germanium or amorphous silicon carbide, or II such as CdS or Cu ₂ S
-VI and III-V compound semiconductors such as GaAs and GaAlAs. In particular, a thin-film photovoltaic element using an amorphous semiconductor or a polycrystalline semiconductor for the photovoltaic generation layer can produce a film having a larger area than a photovoltaic element using single-crystal silicon. It has advantages such as being thin and being able to be deposited on an arbitrary substrate material, and is considered promising.

However, the above thin-film photovoltaic device has
The photoelectric conversion efficiency of a photovoltaic device using single-crystal silicon has not been obtained, and improvement of the photoelectric conversion efficiency and reliability have been issues to be studied for practical use as a power device. .

Accordingly, various methods have been studied as means for improving the photoelectric conversion efficiency of the thin-film photovoltaic device.

One of the important issues for improving the photoelectric conversion efficiency of a thin-film photovoltaic element is to increase light absorption in a thin-film semiconductor layer and to improve short-circuit current (Jsc). This is because if the semiconductor layer is thinned for cost reduction, light absorption is reduced as compared with a bulk semiconductor. As a technology to increase light absorption in the thin film semiconductor layer,
There are the following five techniques.

(1) Opposite to the light incident side of the photovoltaic element,
There is known a technique for forming a reflective layer using a metal film having a high reflectivity, such as Ag, Al, Cu, and Au. This technology uses light transmitted through a semiconductor layer to generate carriers,
By reflecting the light on the reflection layer, the light is absorbed again in the semiconductor layer, the light absorption in the thin film semiconductor layer is increased, the output current is increased, and the photoelectric conversion efficiency is improved.

(2) Methods of improving the surface properties of a substrate by interposing a transparent conductive layer between a back electrode and a semiconductor layer are disclosed in JP-B-59-43101 (manufactured by Fuji Electric) and JP-B-60-41878. It is disclosed in the gazette (Sharp). In these publications, the effect of interposing a transparent conductive layer between the back electrode and the semiconductor layer is to improve the flatness of the back electrode, improve the adhesion of the semiconductor layer, or alloy the metal of the back electrode with the semiconductor layer. Prevention and so on.

(3) Japanese Patent Application Laid-Open No. 60-84888 (Energy Conversion Device) discloses that a transparent conductive layer is interposed as a barrier layer between a back electrode and a semiconductor layer, so that a defect region of a semiconductor layer can be formed. There is disclosed a technique for reducing a current flowing through a device.

(4) By interposing a transparent conductive layer of TiO ₂ between the back electrode of Ag and the semiconductor layer of amorphous silicon, the spectral sensitivity of the solar cell is improved.
The increase in the sensitivity in the long wavelength region is explained by Y. Hamakawa, et.al,
Appl. Phys. Lett., 43 (1983) p644.

(5) By forming the back electrode into a concavo-convex shape (texture structure) having a size approximately equal to the wavelength of light that scatters light, long-wavelength light that cannot be completely absorbed by the semiconductor layer is scattered. T. Tiedje, et.al, Pro has developed a technology to extend the optical path length in the layer, improve the long-wavelength sensitivity of the photovoltaic element, increase the short-circuit current, and improve the photoelectric conversion efficiency.
c. 16th IEEE Photovoltaic Specialist Conf. (1982) p
1423 and H. Deckman, et.al, Proc. 16th IEEE Phot
ovoltaic Specialist Conf. (1982) p1425.

By synthesizing the above techniques, a metal film having a concave-convex shape having a size approximately equal to the wavelength of light that scatters light and having a high reflectance is formed as a back surface reflection layer also serving as a back surface electrode. A configuration in which a transparent conductive layer is interposed between the back reflection layer and the semiconductor layer is considered to be most suitable.

However, when the photovoltaic element is actually manufactured by employing the back electrode having such a configuration, the following four problems are raised from the viewpoint of workability and durability.

(A) A typical typical uneven structure called a conventional so-called texture structure is described in T. Tiedje, et.al, Proc.
16th IEEE Photovoltaic Specialist Conf. (1982) p14
It has been considered that a material having pyramid-shaped irregularities as shown in FIG. 23 has an excellent light confinement effect. However, when an electrode and a semiconductor layer are formed on a substrate having such a surface shape, the leak current of the photovoltaic element increases through a defective portion of the semiconductor layer and the like, and the production yield of the photovoltaic element may decrease. there were. In addition, since the semiconductor layer formed on the surface having pyramid-shaped irregularities has a smaller effective film thickness than the semiconductor layer formed on the flat surface, the originally designed thin doping layer is further thinned. In some cases, the open-circuit voltage (Voc) and the fill factor (FF) of the photovoltaic element are lower than those of the photovoltaic element formed on the flat substrate surface.

(B) For example, when Ag or Cu is used as the back metal reflection layer, when the humidity is high and a positive bias voltage is applied to the back metal reflection layer, Ag or Cu migrates, and light incidence occurs. It turned out that the electrode on the side was conducting, and the photovoltaic element was shunted (short-circuited). This phenomenon was remarkable when the back metal reflective layer had an uneven shape (texture structure) having a size of about the wavelength of light.

(C) When Al is used as the back metal reflection layer, migration such as Ag or Cu does not occur, but when a texture structure is formed, the reflectance may decrease. Furthermore, when a transparent conductive layer is laminated on Al having a texture structure, the reflectance may be significantly reduced.

(D) When the substrate and the back surface reflection layer are formed not flat but uneven, the light scattering on the back surface is small, so that the light absorption in the semiconductor layer is not sufficient. Depending on the combination of the materials of the electrodes, the adhesion between the substrate and the backside reflective layer is insufficient, and there has been a problem that peeling may occur between the substrate and the backside reflective layer in the photovoltaic element processing step.

The above problems are caused by using low-cost substrates such as resin films and stainless steel, and increasing the production speed by increasing the formation speed of semiconductor layers. This is particularly noticeable when the process is employed, and has been a factor in lowering the production yield of the photovoltaic element.

[0022]

SUMMARY OF THE INVENTION The present invention solves the problems of workability, yield, and durability as described above by making the substrate a new structure, and further increases the light absorption of the semiconductor layer. It is another object of the present invention to provide a thin-film photovoltaic element which can be produced at a high yield, has high reliability, and has a high photoelectric conversion efficiency, at a low cost suitable for practical use.

[0023]

Means for Solving the Problems The present inventors have overcome the above-mentioned problems of processability and reliability, and have increased the light absorption of the semiconductor layer and at the same time have a photovoltaic device excellent in processability and reliability. As a result of intensive studies on a new structure and a method for forming a polycrystalline thin film in order to obtain a power device, the photovoltaic device of the present invention provided with a polycrystalline thin film having the following configuration has been achieved.

That is, first, in a photovoltaic device having a polycrystalline thin film and a non-single-crystal semiconductor on a substrate, the polycrystalline thin film has a flat surface of individual crystal grains of the polycrystalline thin film. The photovoltaic device is characterized in that the polycrystalline thin film has a difference in properties, and the surface of the polycrystalline thin film includes a mixture of polycrystalline grains having a surface with irregularities and polycrystalline grains having a flat surface.

Second, the photovoltaic device according to claim 1, wherein the surface of the substrate has irregularities.

Thirdly, the photovoltaic device according to claim 1 or 2, wherein a main material constituting the polycrystalline thin film is a metal or an alloy.

Fourth, the main material constituting the polycrystalline thin film is a metal having a high reflectance from visible to infrared light, such as gold, silver, copper, aluminum, and magnesium. Item 4. The photovoltaic element according to any one of Items 1 to 3.

Fifth, a photovoltaic device according to any one of claims 1 to 4, wherein a transparent conductive layer is formed between the polycrystalline thin film and the non-single-crystal semiconductor. Element.

Sixth, the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film, wherein: It is a photovoltaic element of item.

Seventh, the polycrystalline thin film is a transparent conductive layer.
It is a photovoltaic element of item.

Eighth, the surface of the photovoltaic element has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film. 2. The photovoltaic element according to item 1.

Ninth, the surface of the polycrystalline thin film is provided with a step along the grain boundary of the polycrystal or a ridge or depression at the grain boundary portion of the polycrystal. 9. The photovoltaic element according to any one of 1 to 8.

Tenth, the difference in flatness of the surface of each crystal grain of the polycrystalline thin film is 0.01 μm as the difference of Rmax.
10 to 1.5 μm.
The photovoltaic device according to any one of the above items.

Eleventh, the photovoltaic device according to any one of claims 1 to 10, wherein the polycrystalline thin film has a polycrystalline average particle diameter of 0.1 μm to 2 mm. Element.

In a twelfth aspect, the photovoltaic device according to any one of claims 1 to 11, wherein the irregularities provided on the surface of the substrate have a Rmax of 0.01 μm to 1 μm. is there.

A thirteenth feature is that a height or a depth of a step, a bulge, or a depression along a grain boundary of the polycrystalline thin film is 0.01 μm to 2 μm on the surface of the polycrystalline thin film. The photovoltaic device according to any one of claims 1 to 12, wherein

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of each claim according to the present invention will be described below.

According to the first aspect of the present invention, in the photovoltaic device in which a polycrystalline thin film is formed on a substrate and a non-single-crystal semiconductor is formed on the polycrystalline thin film, There is a difference in the flatness of the surfaces of the individual crystal grains of the thin film, and the polycrystalline thin film has a mixture of polycrystal grains having a surface with irregularities and polycrystal grains having a flat surface. The use of the high quality thin film has the following effects.

First, the adhesion between the thin film laminated on the polycrystalline thin film and the polycrystalline thin film is improved as compared with the case where a conventional polycrystalline thin film having a flat surface is used. In the process, peeling between the polycrystalline thin film and the thin film laminated thereon is eliminated, and the controllability and the degree of freedom of the manufacturing process are improved, and the production yield of the photovoltaic element is improved. In addition, as a result of accelerated weather resistance tests such as a high-temperature and high-humidity cycle test and a salt water test, weather resistance was improved. Furthermore, as a result of mechanical strength tests such as a scratch test and a bending test,
Durability improved. In addition, irregular reflection on the back surface of the photovoltaic element increases due to unevenness of the surface of the polycrystalline thin film,
The long-wavelength light that could not be absorbed by the semiconductor layer was scattered, the optical path length in the semiconductor layer was extended, the short-circuit current (Jsc) of the photovoltaic element was increased, and the photoelectric conversion efficiency was improved. Also,
The series resistance of the photovoltaic element was reduced, the fill factor (FF) was improved, and the photoelectric conversion efficiency was improved. It is not clear how the series resistance is reduced, but the improved adhesion between the thin film laminated on the polycrystalline thin film and the polycrystalline thin film, and furthermore, the surface of the polycrystalline thin film In the case of processing as in the present invention, since etching is performed physically or chemically in a gas phase or a liquid phase, impurities on the surface of the polycrystalline thin film are removed, and an oxide layer on the surface of the polycrystalline thin film is removed. May be removed.

Further, as compared with the case of using a conventional polycrystalline thin film having uniformly formed irregularities on the surface, the leak current of the photovoltaic element is reduced, and the production yield of the photovoltaic element is improved. . Further, the open-circuit voltage (Voc) and the fill factor (FF) were improved while the short-circuit current (Jsc) of the photovoltaic element was maintained at a high value, and the photoelectric conversion efficiency was improved. This effect is considered as follows. That is, the conventional so-called texture structure was a pyramid-shaped unevenness or similar to that as described above.
If the unevenness is increased to enhance the light scattering effect, a defective portion of the semiconductor layer is likely to occur at the peak of the pyramid. However, in the case of the photovoltaic device of the present invention, the unevenness is formed only at one time. It is considered that the defect portion of the semiconductor layer is less likely to occur because the polycrystalline grain of the portion is relatively flat and the surface of the other polycrystalline grain is relatively flat. In addition, since the semiconductor layer formed on the surface having pyramid-shaped irregularities has a smaller effective film thickness than the semiconductor layer formed on the flat surface, the originally designed thin doping layer is further thinned. In some cases, the open-circuit voltage (Voc) and the fill factor (FF) of the photovoltaic element are lower than those of the photovoltaic element formed on the flat substrate surface. In this case, since the polycrystalline grains having the irregularities and the flat polycrystalline grains are mixed, the portion where the semiconductor layer is thinned is reduced, and the short-circuit current (Jsc) is high due to the light scattering due to the irregularities.
It is considered that the open-circuit voltage (Voc) and the fill factor (FF) were improved while maintaining the above.

Further, when the thin film laminated on the polycrystalline thin film is also polycrystalline, the orientation of the polycrystalline thin film laminated thereon is improved, the average grain size of the polycrystal is increased, and The variation in crystal grain size was reduced. As a result, the series resistance of the photovoltaic element decreases, and the fill factor (FF)
At the same time, light scattering was further promoted and the short-circuit current (Jsc) increased. This effect is considered as follows. First, regarding the orientation, it is considered that the unevenness differs according to the grain boundaries of the polycrystal of the substrate, and the plane orientation is clearly separated, so that the plane orientation of the thin film grown thereon becomes easier to be uniform. Regarding the average grain size of the polycrystal of the thin film laminated thereon, compared to a flat surface or a surface having pyramid-shaped irregularities, polycrystalline grains having irregularities and flat polycrystalline grains are mixed. This is considered to be because the nucleation density of the polycrystalline thin film grown thereby decreased and the nucleation became uniform.

According to the second aspect of the present invention, since the surface of the substrate has irregularities, the adhesion between the substrate and the polycrystalline thin film is improved, and the controllability and the degree of freedom in the manufacturing process of the photovoltaic element are improved. At the same time, the production yield of the photovoltaic element was improved, and the weather resistance and durability of the photovoltaic element were also improved.

According to the third aspect of the present invention, since the main material constituting the polycrystalline thin film is a metal or an alloy, it functions as a back electrode of the photovoltaic element. Further, it is easy to make a difference in the flatness of the surface of each crystal grain of the polycrystalline thin film. Further, it becomes easy to form polycrystals having a particle size suitable for the use of the present invention. When the substrate is a metal or an alloy, the adhesion between the substrate and the polycrystalline thin film is improved.

According to the fourth aspect of the present invention, the main material constituting the polycrystalline thin film is a metal having high reflectance from visible to infrared light, such as gold, silver, copper, aluminum, and magnesium. Has the following effects.

That is, the reflectivity of the back surface of the photovoltaic element was further improved, the light absorption of the semiconductor layer was increased, and the short-circuit current (Jsc) of the photovoltaic element was further improved.

When the polycrystalline thin film made of a metal having a high reflectance has a conventional pyramid-shaped uneven texture structure, the metal having a high reflectance diffuses into the semiconductor layer or causes migration. However, in the case of the polycrystalline thin film of the present invention, there is a difference in the flatness of the surface of individual crystal grains of the polycrystal, and polycrystal grains having irregularities formed on the surface. And high polycrystalline grains having a flat surface, the above-mentioned metal with high reflectivity may diffuse into the semiconductor layer or cause migration while maintaining high diffuse reflection and high short-circuit current (Jsc). Almost disappeared, and the production yield of the photovoltaic element was significantly improved. Also, the leakage current of the photovoltaic element decreases, and the open circuit voltage (Voc) and the fill factor (F
F) improved.

Further, the main materials of the polycrystalline thin film include:
The use of aluminum is most preferable because of its low manufacturing cost and the fact that migration is less likely to occur than silver and copper.However, a polycrystalline thin film of aluminum has a conventional pyramid-shaped uneven texture structure. Then, the total reflectance of the aluminum surface often decreases. Further, when a transparent conductive layer is laminated on the above-mentioned polycrystalline thin film of aluminum, the total reflectance is often further reduced, and is often unsuitable as a back reflection layer of a photovoltaic element. Was. On the other hand, when a polycrystalline thin film of aluminum having a flat surface is formed, scattering of light on the back surface of the semiconductor layer is reduced and the short-circuit current (Jsc) of the photovoltaic element is reduced. There is a problem that peeling easily occurs between the thin film and the thin film laminated thereon. On the other hand, as in the present invention, the surface of aluminum has a difference in the flatness of the surface of the crystal grains, and the polycrystal grains having irregularities on the surface and the polycrystal grains having the flat surface are mixed. As a result, the light is scattered on the back surface, and the total reflectance on the aluminum surface is not reduced even when the transparent conductive layer is laminated. The high total reflectance on the aluminum surface improves the light absorption of the semiconductor layer. However, the short-circuit current (Jsc) of the photovoltaic element was improved. In addition, the adhesion between aluminum and the thin film laminated on it is also improved, the flexibility and controllability of the manufacturing process are improved, the manufacturing yield is improved, and the weather resistance and durability of the photovoltaic element are improved. did.

The reason why the total reflectance of the aluminum surface having a pyramid-shaped irregular texture structure over the entire surface is lowered is not clear, but the minute pyramid-shaped irregularities on the order of the wavelength of light cause the aluminum to have a low reflectance. It is considered that the surface area increases, a reaction easily occurs at the interface with the transparent conductive layer, and a compound is formed at the interface, thereby lowering the reflectance. In the configuration of the present invention, there is a difference in the flatness of the surface of individual crystal grains of aluminum, and polycrystalline grains having irregularities formed on the surface and polycrystal grains having a flat surface are mixed, so that aluminum It is considered that the increase in the surface area was suppressed, the reaction at the interface with the transparent conductive layer was suppressed, and the total reflectance was greatly improved.

According to the fifth aspect of the present invention, the following effects are obtained by forming a transparent conductive layer between the polycrystalline thin film and the non-single-crystal semiconductor.

That is, the combination of the polycrystalline thin film also serving as the backside reflection layer and the transparent conductive layer improves the reflectance of the backside of the photovoltaic element, especially for long-wavelength light. The optical path length in the semiconductor layer is extended, the light absorption is increased, and the short-circuit current (Jsc) of the photovoltaic element is further increased by the synergistic effect that the irregular reflection is improved by the polycrystalline thin film having Conversion efficiency was further improved. In addition, by improving the adhesion between the polycrystalline thin film and the transparent conductive layer, and by reducing the current flowing in the defect region of the semiconductor layer by the transparent conductive layer having an appropriate resistance value. Thus, the degree of freedom and controllability of the manufacturing process of the photovoltaic element were improved, the production yield was improved, and the weather resistance and durability of the photovoltaic element were improved. Also,
When the polycrystalline thin film has the features of claim 1, the orientation of the transparent conductive layer is improved, the average grain size of the polycrystal of the transparent conductive layer is increased, and the variation of the grain size is reduced. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

According to the sixth aspect of the present invention, the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film, and the surface of the polycrystalline thin film has irregularities. And a region having a flat surface coexist with the following effects.

That is, by improving the adhesion between the transparent conductive layer and the semiconductor layer, the degree of freedom and controllability of the manufacturing process of the photovoltaic device are further improved, and the production yield is further improved, and the photovoltaic device is improved. The weather resistance and durability were further improved. In the case where pyramid-shaped irregularities are formed on the entire surface of the transparent conductive layer, a defective portion of the semiconductor layer is likely to be formed on a mountain portion of the pyramid, and the photovoltaic element shunts or an open voltage ( Voc) and fill factor (FF) may be reduced, but as in the present invention, the surface of the transparent conductive layer has a difference in flatness according to the polycrystalline grain boundaries of the polycrystalline thin film. , By mixing the area where the surface is uneven and the area where the surface is flat,
Light scattering at the interface between the transparent conductive layer and the semiconductor layer is promoted while maintaining a high yield of the photovoltaic element and a high open circuit voltage (Voc) and a fill factor (FF), thereby causing a short circuit. The current (Jsc) further increased.

According to the seventh aspect of the present invention, the following effects are obtained by the fact that the polycrystalline thin film is a transparent conductive layer.

In other words, even when the substrate is a photovoltaic element configured to transmit light and receive light from the substrate side, light scattering on the light incident side of the photovoltaic element causes a high short-circuit current ( While maintaining Jsc), the controllability and flexibility of the manufacturing process of the photovoltaic element were improved, the production yield was improved, and the light resistance and durability of the photovoltaic element were improved. Also,
In the case where pyramid-shaped irregularities are formed on the entire surface of the transparent conductive film, defects in the semiconductor layer are apt to occur at the peaks of the pyramid, and the photovoltaic element shunts and the open-circuit voltage (Voc) And fill factor (FF)
However, as in the present invention, the surface of the transparent conductive layer film has a difference in flatness according to the polycrystalline grain boundary, and the surface of the polycrystalline grain having irregularities formed on the surface is different from the surface of the transparent conductive layer film. A high open-circuit voltage (Voc) is maintained while maintaining a high yield of the photovoltaic element due to the mixture of flat polycrystalline grains.
While maintaining the fill factor (FF), light scattering at the interface between the transparent conductive layer and the semiconductor layer was promoted, and the short-circuit current (Jsc) was further increased.

According to the invention of claim 8, the surface of the photovoltaic element has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film, and irregularities are formed on the surface. The mixture of the region and the flat surface promotes the scattering of light at the light incident side of the photovoltaic element, particularly at the interface between the semiconductor layer and the upper transparent electrode. The light will be scattered on both sides, further increasing the optical path length in the semiconductor layer, increasing light absorption and short circuit current (Jsc)
Increased further.

According to the ninth aspect of the present invention, the surface of the polycrystalline thin film is provided with a step along the grain boundary of the polycrystal or a bulge or a depression at the grain boundary portion of the polycrystal. The adhesion between the thin film laminated on the polycrystalline thin film and the polycrystalline thin film is further improved, the degree of freedom and controllability of the manufacturing process of the photovoltaic element are further improved, and the production yield is further improved. However, the weather resistance and durability of the photovoltaic element were further improved. In addition, due to steps or irregularities in the crystal grain boundaries on the surface of the polycrystalline thin film, irregular reflection on the back surface of the photovoltaic element increases, and long-wavelength light that could not be absorbed by the semiconductor layer is scattered in the semiconductor layer. , The short-circuit current (Jsc) of the photovoltaic element further increased, and the photoelectric conversion efficiency was further improved. Further, the orientation of the thin film laminated on the polycrystalline thin film was further improved, and the average grain size of the polycrystal of the thin film was further increased. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

Hereinafter, embodiments of the present invention will be described.

(Photovoltaic Element) Examples of the photovoltaic element according to the present invention include those shown in FIGS. Hereinafter, the configuration of the photovoltaic element of the present invention and the method of manufacturing the same will be described in more detail with reference to the drawings.

FIG. 1 is an example of a sectional view of a photovoltaic element for explaining the concept of the present invention in detail. However, the present invention is not limited to the photovoltaic element having the configuration shown in FIG. In FIG. 1, 101 is a substrate, 102 is a back metal reflective layer, 103 is a transparent conductive layer, 104 is an n-type semiconductor layer, 1
05 is an i-type semiconductor layer, 106 is a p-type semiconductor layer, 107 is a transparent electrode, and 108 is a current collecting electrode. FIG. 1 shows a configuration in which light enters from the p-type semiconductor layer side. In the case of a photovoltaic element having a configuration in which light enters from the n-type semiconductor layer side,
Is a p-type semiconductor layer, and 106 is an n-type semiconductor layer.

FIG. 1 shows a configuration in which light is incident from the side opposite to the substrate. However, in a photovoltaic element having a configuration in which light is incident from the substrate side, the layers are arranged in the reverse order to FIG. 1 except for the substrate. May be laminated.

FIG. 2 is an example of a sectional view of a stack type photovoltaic device for explaining the concept of the present invention in detail. The stack type photovoltaic device of the present invention shown in FIG.
215 is a first pin junction counted from the light incident side, 216 is a second pin junction, and 217 is a third pin junction. These three pin junctions are formed on the substrate 201 on the backside metal reflection layer 2.
02 and a transparent conductive layer 203 are formed and laminated thereon. The transparent electrode 2 is formed on the top of the three pin junctions.
13 and the collecting electrode 214 are formed to form a stacked photovoltaic element. The respective pin junctions are formed by n-type semiconductor layers 204, 207, 210, i-type semiconductor layers 205, 208, 211, p-type semiconductor layers 206,
09, 212. Further, as in the photovoltaic element of FIG. 1, the arrangement of the doping layers and the electrodes may be switched depending on the incident direction of light.

Hereinafter, the respective layers of the photovoltaic element of the present invention will be described in detail in the order of formation.

(Substrate) In the present invention, the semiconductor layers 104-1
Since 06 and 204 to 212 are thin films having a thickness of at most about 1 μm, they are deposited on an appropriate substrate. Such a substrate 10
1, 201 may be a single crystalline or non-single crystalline one, and furthermore, they may be conductive or electrically insulating. Further, they may be light-transmitting or non-light-transmitting, but preferably have a small amount of deformation and distortion and a desired strength. Specifically, F
e, Ni, Cr, Al, Mo, Au, Nb, Ta, V,
Metals such as Ti, Pt, Pb or alloys thereof, for example, brass, thin plates such as stainless steel and composites thereof, and polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride, polystyrene, polyamide, Films or sheets of heat-resistant synthetic resin such as polyimide or epoxy, or composites of these with glass fiber, carbon fiber, boron fiber, metal fiber, etc., and metals of different materials on the surface of thin plates of these metals, resin sheets, etc. Thin film and / or SiO ₂ , Si ₃ N ₄ , Al ₂ O ₃ , A
Examples thereof include those obtained by subjecting an insulating thin film such as 1N to a surface coating treatment by a sputtering method, an evaporation method, a plating method, or the like, glass, ceramics, and the like.

When the substrate is electrically conductive such as a metal, it may be used as an electrode for direct current extraction. When the substrate is electrically insulating such as a synthetic resin, the surface on the side on which the deposited film is formed may be made of Al. , Ag, Pt, Au, Ni, Ti, Mo, W,
Fe, V, Cr, Cu, stainless steel, brass, nichrome, so-called simple metals or alloys such as SnO ₂ , In ₂ O ₃ , ZnO, ITO, etc., and transparent conductive oxide (TCO) by plating, vapor deposition, sputtering, etc. It is desirable to form a current extraction electrode by performing a surface treatment in advance by a method.

Of course, even if the substrate is made of an electrically conductive material such as metal, the reflectance of long-wavelength light on the substrate surface can be improved, and the mutual interaction of constituent elements between the substrate material and the deposited film can be improved. A different kind of metal layer or the like may be provided on the side of the substrate on which the deposited film is formed for the purpose of preventing diffusion or the like. When the substrate is relatively transparent and a photovoltaic element having a layer structure in which light enters from the side of the substrate is used, a conductive thin film such as the transparent conductive oxide or a metal thin film is previously deposited. It is desirable to form it.

The surface of the substrate may be a so-called smooth surface, but it is more preferable to have a fine uneven surface.

Conventionally, the purpose was to scatter light on the substrate surface due to the unevenness of the substrate surface. Therefore, it was desired that Rmax be larger than the wavelength of light. Since the polycrystalline thin film formed on the substrate approaches the conventional so-called textured structure, the leakage current increases and the shunt or open circuit voltage (Voc) or fill factor (FF) of the photovoltaic element is increased.
The problem of the conventional texture structure, such as the decrease of the texture, appears. Further, when the Rmax of the substrate surface is too small and close to a mirror surface, the adhesion may be reduced depending on the combination of the material of the substrate and the material of the polycrystalline thin film formed thereon, which may cause a problem of peeling.

Therefore, in the case of forming a fine uneven surface, it is desirable that the uneven shape is spherical, conical, pyramidal, or the like, and that the maximum height (Rmax) is equal to or less than the wavelength of light. . That is, preferably 0.01 μm to 1 μm
m, more preferably 0.02 μm to 0.5 μm. As a result, the adhesion between the substrate and the polycrystalline thin film could be improved without causing the problem of the conventional texture structure. As a result, the selectivity of materials for the substrate and the polycrystalline thin film is improved, the controllability and flexibility of the manufacturing process of the photovoltaic element are improved, the production yield is improved, and the weather resistance of the photovoltaic element is improved. And durability have been improved.

The shape of the substrate may be a plate having a smooth surface or an uneven surface, a long belt shape, a cylindrical shape, or the like, depending on the application, and the thickness thereof may form a desired photovoltaic element. However, when flexibility is required as the photovoltaic element, or when light is incident from the side of the substrate, as much as possible within the range where the function as the substrate is sufficiently exhibited. It can be thin. However, from the viewpoints of mechanical strength and the like in manufacturing and handling the substrate,
It is 10 μm or more.

(Polycrystalline Thin Film) The polycrystalline thin film according to the present invention is a feature of the present invention, and is particularly characterized by its crystal form and surface shape.

As a crystal form, a polycrystalline form is used and is formed on the substrate.

As a result of the study, the present inventors have found that the surface shape of the polycrystalline thin film has a difference in the flatness of the surface of each crystal grain of the polycrystalline thin film, and that the surface of the polycrystalline thin film has irregularities. It has been found that a shape in which a polycrystalline grain having a surface with a surface and a polycrystalline grain having a flat surface are mixed is preferable.

Further, if the difference in the flatness of the surface of each crystal grain of the polycrystal is too small, that is, it means that the surface is flat over the entire surface of the substrate or a texture structure is formed over the entire surface. In this case as well, it has been found that conventional problems such as a decrease in light scattering or an increase in leak current of the photovoltaic element appear. In addition, if the difference in flatness of the surfaces of the individual crystal grains of the polycrystal is too large, there are polycrystal grains having large irregularities on the surface. It has been found that problems such as an increase in the shunt or leak current of the photovoltaic element and a decrease in the open circuit voltage (Voc) or the fill factor (FF) appear.

Therefore, the difference in the flatness of the surface of each individual crystal grain of the polycrystal is the difference in Rmax, preferably 0.01%.
It has been found that a thickness of from μm to 1.5 μm, more preferably from 0.02 μm to 1 μm, optimally from 0.05 μm to 0.7 μm is desirable.

If the average grain size of the polycrystal is too small (less than 0.05 μm), it tends to be either flat over the entire surface of the substrate or a textured structure over the entire surface. In this case as well, conventional problems such as a decrease in light scattering, an increase in leak current of the photovoltaic element, and a decrease in shunt or open-circuit voltage (Voc) or fill factor (FF) of the photovoltaic element appear. I understood. It was also found that when the average grain size of the polycrystal was too large (exceeding 2 mm), irregular reflection on the back surface of the photovoltaic element was reduced, and the short-circuit current (Jsc) was reduced.

Therefore, the average particle size of the polycrystal is preferably 0.1 μm to 2 mm, more preferably 0.2 μm to 2 mm.
μm to 1 mm, optimally 0.5 μm to 100 μm
Is desirable.

Further, in a photovoltaic element in which a step is provided along the polycrystalline grain boundary on the surface of the polycrystalline thin film, or a protrusion or a depression is provided in the polycrystalline grain boundary, the polycrystalline thin film is polycrystalline. If the height of the steps or irregularities along the grain boundaries is too small, the scattering of light will decrease, and the short-circuit current (Jsc) of the photovoltaic device will decrease. It has been found that the leakage current of the power element may increase and lower the manufacturing yield.

Therefore, the height of the step on the surface of the polycrystalline thin film along the polycrystalline grain boundary, or the height or depth of the protrusion or dent at the polycrystalline grain boundary is preferably
0.01 μm to 2 μm, more preferably 0.02 μm
m to 1.5 μm, optimally 0.03 μm to 1 μm
Turned out to be desirable. Further, it is preferable that the flatness of the surface within each crystal grain is smaller than the height of the step or the unevenness along the grain boundary of the polycrystal. If the Rmax of the surface in each crystal grain is large, it approaches a conventional so-called texture structure, so that the leakage current increases, the shunt or open circuit voltage (Voc) or the fill factor (FF) of the photovoltaic element decreases. The problem of the conventional texture structure comes out. Therefore, the preferable range of the flatness of the surface within each crystal grain varies depending on the height of the steps or irregularities along the grain boundaries of the polycrystal, but is preferably 2 μm or less in Rmax, more preferably Rmax. 1.5 μm or less, optimally Rmax 1
μm or less is desirable.

The material of the polycrystalline thin film may be a conductive material or an electrically insulating material. Further, they may be translucent or non-translucent, but need heat resistance and durability that can withstand the manufacturing process of the photovoltaic element. Specifically, Fe, Ni, Cr, Al, Mg, Mo, Au,
Metals such as Nb, Ta, V, Ti, Pt, Pb or alloys thereof, for example, polycrystalline materials of brass, stainless steel, etc. and composites thereof, or SiO ₂ , Si ₃ N ₄ , Al ₂ O
₃ , insulating polycrystalline material containing AlN, etc., or
In ₂ O ₃ , SnO ₂ , IT
O (In ₂ O ₃ + SnO ₂ ), ZnO, CdO, Cd ₂ Sn
O ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂ O ₃ , MoO ₃ , Na _x W
A conductive oxide such as O ₃ , a mixture thereof, or a compound obtained by adding a dopant to these compounds can be used.

When the polycrystalline thin film is an electrically conductive material such as a metal, it may be used as an electrode for direct current extraction. When the polycrystalline thin film is insulative, a conductive thin film is laminated to form an electrode for extracting current.

Of course, even if the polycrystalline thin film is made of an electrically conductive material such as a metal, the reflectance of long wavelength light on the substrate surface can be improved, or the distance between the polycrystalline thin film and the semiconductor layer can be increased. The polycrystalline thin film may be formed of a laminated film composed of two or more layers for the purpose of preventing mutual diffusion of the constituent elements described above.

In the case of a photovoltaic element in which light enters the semiconductor layer from the side opposite to the substrate, the polycrystalline thin films 102 and 202 which are the feature of the present invention are arranged on the back surface of the semiconductor layer in the light incident direction. In addition, it also functions as a light reflection layer that reflects light that could not be absorbed by the semiconductor layer back to the semiconductor layer, and also as a back electrode of the photovoltaic element. In this case, among the aforementioned materials, metals having high reflectivity, such as aluminum, magnesium, copper, silver, and gold, are particularly preferable. By using a metal having a high reflectivity, light that could not be absorbed by the semiconductor layer is reflected again by the semiconductor layer with a high reflectivity, the optical path length in the semiconductor layer is determined, and light absorption of the semiconductor layer increases. As a result, the short-circuit current (Jsc) of the photovoltaic element increases.

As a method of forming a polycrystalline thin film, microwave plasma CVD, RF plasma CVD, light CV
Various CVD methods such as D method, thermal CVD method, MOCVD method,
Alternatively, various evaporation methods such as EB evaporation, sputter evaporation, MBE, ion plating, and ion beam, or a plating method, a printing method, and the like are used. In order to process the surface of the polycrystalline thin film so as to have the features of the present invention, the following method can be used.

(Method of Surface Treatment of Polycrystalline Thin Film) The method of forming a polycrystalline thin film, which is a feature of the present invention, is as follows.
Depending on the material of the polycrystalline thin film, the following method can be employed.

That is, there is a difference in the flatness of the surface of each crystal grain of the polycrystalline thin film, and the polycrystalline thin film has a polycrystalline thin film having an uneven surface and a polycrystalline thin film having a flat surface. In order to mix crystal grains, anisotropic etching in which the etching rate differs depending on the plane orientation of the polycrystal exposed on the surface of the polycrystalline thin film is physically or chemically performed in the gas phase or the liquid phase. It is obtained by doing.

More specifically, when the etching is performed in the gas phase, gas etching, plasma etching, ion etching, or the like can be used. As the etching gas, CF ₄ ,
C ₂ F ₆ , C ₃ F ₈ , C ₄ F ₁₀ , CHF ₃ , CH ₂ F ₂ , C
l ₂ , ClF ₃ , CCl ₄ , CCl ₂ F ₂ , CCIF ₃ , CH
ClF ₂ , C ₂ Cl ₂ F ₄ , BCl ₃ , PCl ₃ , CBr
F ₃ , SF ₆ , SiF ₄ , SiCl ₄ , HF, O ₂ , N ₂ , H
₂ , He, Ne, Ar, Xe and the like or a mixed gas thereof. The gas pressure in the case of plasma etching is 10 ⁻³ Torr to 1 Torr, and DC or AC or 1
A high frequency such as an RF wave of 100 MHz or a microwave of 0.1 to 10 GHz can be used.

When the reaction is carried out in a liquid phase, examples of the acid include
Sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, hydrofluoric acid, chromic acid, sulfamic acid, oxalic acid, tartaric acid, citric acid, formic acid, lactic acid,
Glycolic acid, acetic acid, gluconic acid, succinic acid, malic acid, etc., or those diluted with water, or a mixture thereof can be used. Examples of the alkali include sodium hydroxide, ammonium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, sodium first phosphate, sodium second phosphate, sodium third tertiary phosphate, sodium pyrophosphate, and sodium tripolyphosphate. Sodium acid, sodium tetrapolyphosphate, sodium trimetaphosphate, sodium tetrametaphosphate, sodium hexametaphosphate, sodium orthosilicate, sodium metasilicate, etc., or those obtained by diluting them with water or using a mixture thereof Can be. When etching is performed in a liquid phase, the etching liquid may be heated or energy such as ultrasonic waves may be applied.

Further, the preferable etching conditions cannot be specified unconditionally because they vary greatly depending on the material or surface shape of the polycrystalline thin film. However, as an example, an aluminum thin film having a thickness of 0.5 μm is as follows. Conditions are preferred.

For example, when etching is performed in a gas phase, 47
Stainless steel cut into mm square (SUS430-BA)
Ar was introduced at a flow rate of 20 to 150 sccm and a gas pressure of 4 was set in a state in which an aluminum thin film having a thickness of 0.4 μm was formed on a substrate and set in a substrate holder of a sputtering apparatus.
１００100 mTorr and 100WＷ4 on the substrate side
Applying a RF high frequency of 13.56 MHz of 00W to Ar
It is desirable to generate plasma and etch the substrate surface by Ar plasma treatment for 2 to 20 minutes.
Of course, other etching gas may be used, and plasma may be generated by other energy such as DC power or microwave. In that case, naturally, suitable conditions differ depending on the gas and energy.

When the above-mentioned aluminum thin film is etched in a liquid phase, for example, phosphoric acid, nitric acid and water are mixed in a ratio of 3:
It is desirable to perform etching for 0.2 to 5 minutes while stirring with an etching solution mixed at a ratio of 1:20. Of course, other etchants such as a mixture of hydrofluoric acid, nitric acid, acetic acid, and water can be used. The preferred etching time varies depending on the type of etching solution or the mixing ratio. In the case of an acid or alkali having a strong etching effect on a certain polycrystalline thin film material, it is desirable to increase the dilution rate and to shorten the etching time.

In both the gas phase etching and the liquid phase etching, it is preferable that the etching condition be stronger as the surface state of the formed polycrystalline thin film is closer to the mirror surface. Further, the preferred etching conditions also differ depending on the change in the composition of the polycrystalline thin film or the amount of impurities mixed in the polycrystalline thin film. Further, suitable etching conditions also differ depending on the thickness of the polycrystalline thin film. If the composition and surface properties of the polycrystalline thin film are the same, etching conditions that are generally stronger are preferred when the polycrystalline thin film is thicker than when it is thin.

(Back Metal Reflective Layer) In the present invention, in the case of a photovoltaic element in which the substrate is translucent and light enters from the substrate side, after forming the semiconductor layer, the back metal reflective layer also serving as the back electrode is formed. May be laminated.

The back metal reflection layer reflects the long-wavelength light that could not be absorbed by the semiconductor layer again to the semiconductor layer, extends the optical path length in the semiconductor layer, increases the light absorption of the semiconductor layer, and increases the photovoltaic power. Increase the short-circuit current (Jsc) of the device.

As the material of the back metal reflection layer, gold, silver,
Examples thereof include metals such as copper, aluminum, magnesium, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel. Among them, metals having high reflectivity such as aluminum, magnesium, copper, silver, and gold are particularly preferable.

For the formation of the back metal reflection layer, various vapor deposition methods such as EB vapor deposition and sputter vapor deposition, various CVD methods, plating methods, printing methods and the like are used.

(Transparent Conductive Layer) The transparent conductive layer 1 according to the present invention
Numeral 03 denotes a photovoltaic element which receives light from the substrate side between the polycrystalline thin film 102 and the semiconductor layer 104 in the case of a photovoltaic element which receives light from the opposite side to the substrate mainly for the following purposes. In the case of an element, it is arranged between the back metal reflection layer and the semiconductor layer.

First, irregular reflection on the back surface of the photovoltaic element is improved, light is confined in the photovoltaic element by multiple interference by the thin film, the optical path length in the semiconductor layer is extended, and the short-circuit current of the photovoltaic element is reduced. (Jsc). Next, it is necessary to prevent the polycrystalline thin film 102 also serving as the back electrode or the metal of the back metal reflection layer from diffusing into the semiconductor layer or causing migration, thereby preventing the photovoltaic element from shunting. In addition, by providing the transparent conductive layer with a slight resistance value, a defect such as a pinhole of the semiconductor layer can be caused between the transparent electrode 107 and the polycrystalline thin film 102 or the back metal reflection layer provided with the semiconductor layer interposed therebetween. The purpose is to prevent a short circuit from occurring.

The transparent conductive layer 103 is required to have a high transmittance in a wavelength region where the semiconductor layer can absorb light and to have an appropriate resistivity. Preferably, the transmittance at 650 nm or more is 80% or more, more preferably 85% or more, and optimally 90% or more. Further, the resistivity is preferably 1 × 10 ⁻⁴ Ωcm or more and 1 × 10 ⁶ Ωcm.
Or less, more preferably 1 × 10 ⁻² Ωcm or more, and 5 × 1
0 is desirably ⁴ [Omega] cm or less.

The material of the transparent conductive layer 103 is In ₂
O ₃ , SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ), Zn
O, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂
A conductive oxide such as O ₃ , MoO ₃ , and Na _x WO ₃ or a mixture thereof is preferably used. Further, an element (dopant) that changes the conductivity may be added to these compounds.

As the element (dopant) that changes the conductivity, for example, when the transparent conductive layer 103 is ZnO,
Al, In, B, Ga, Si, F, etc., In the case of In ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb, etc., and in the case of SnO ₂ , F, Sb, P, As, In, T
1, Te, W, Cl, Br, I, etc. are preferably used.

As a method for forming the transparent conductive layer 103, E
Various deposition methods such as B deposition and sputter deposition, various CVD
Method, spray method, spin-on method, dipping method and the like are preferably used.

Although the surface of the transparent conductive layer 103 may be flat, the surface corresponding to the polycrystalline grain boundary of the polycrystalline thin film may be used.
By forming steps, bumps, or depressions, the adhesion between the transparent conductive layer and the semiconductor layer is improved, the degree of freedom and controllability of the photovoltaic element manufacturing process is further improved, and the manufacturing yield is further improved. And the weather resistance of the photovoltaic element,
Durability has been further improved. In addition, light scattering at the interface between the transparent conductive layer and the semiconductor layer was promoted, and the short-circuit current (Jsc) was further increased. Transparent conductive layer 10 corresponding to polycrystalline grain boundaries
The height of the step 3 or the height or depth of the bulge or dent at the polycrystalline grain boundary is preferably 0.0
1 μm to 2 μm, more preferably 0.02 μm to 1.5 μm, and most preferably 0.03 μm to 1 μm.

Further, due to the polycrystalline growth of the transparent conductive layer, irregularities corresponding to the growth surface may be formed on the surface. Also, the polycrystalline thin film has a step, a bump, or a dent corresponding to the polycrystalline grain boundary,
The average grain size of the polycrystal in the transparent conductive layer was increased, light scattering was increased, and the short-circuit current (Jsc) of the photovoltaic device was further improved.

(Semiconductor Layer) As a material of the semiconductor layer according to the present invention, a material using a group IV element such as Si, C, Ge, or the like, or a material using a group IV alloy such as SiGe, SiC, SiSn, or II- such as CdS and CdTe
Using a group VI element, or CuInSe ₂ , C
I-III-V such as u (InGa) Se ₂ , CuInS ₂
Those using an I ₂ group element are used.

Among the above semiconductor materials, semiconductor materials particularly preferably used for the photovoltaic device of the present invention include a-Si: H (abbreviation for hydrogenated amorphous silicon), a
-Si: F, a-Si: H: F, a-SiGe: H, a
-SiGe: F, a-SiGe: H: F, a-SiC:
Group IV and group IV alloy-based amorphous semiconductor materials such as H, a-SiC: F and a-SiC: H: F, microcrystalline semiconductor materials, and polycrystalline semiconductor materials are given.

The semiconductor layer can perform valence electron control and forbidden band width control. Specifically, a raw material compound containing an element serving as a valence electron controlling agent or a forbidden band width controlling agent when forming a semiconductor layer is used alone, or mixed with the deposited film forming raw material gas or the diluent gas to form a film. You only have to introduce it in the space.

The semiconductor layer is controlled by valence electrons.
At least a portion is doped p-type and n-type to form at least one set of pin junctions. And
By stacking a plurality of pin junctions, a so-called stack cell configuration is obtained.

As a method of forming a semiconductor layer, a microwave plasma CVD method, an RF plasma CVD method,
VD method, thermal CVD method, various CVD methods such as MOCVD method, or various evaporation methods such as EB evaporation, MBE, ion plating, ion beam method, sputtering method,
It is formed by a spray method, a printing method, or the like. As a method adopted industrially, a plasma CVD method in which a raw material gas is decomposed by plasma and deposited on a substrate is preferably used. In addition, as the reaction device, a batch type device, a continuous film forming device, or the like can be used as desired.

Hereinafter, a semiconductor layer using a group IV and group IV alloy-based amorphous semiconductor material particularly suitable for the photovoltaic device of the present invention will be described in more detail.

(1) i-type semiconductor layer (intrinsic semiconductor layer) Particularly in a photovoltaic device using a group IV or group IV alloy-based amorphous semiconductor material, an i-type layer used for a pin junction is exposed to irradiation light. It is an important layer for generating and transporting carriers.

As the i-type layer, a slightly p-type or slightly n-type layer can be used.

As described above, the group IV and group IV alloy non-single-crystal semiconductor materials contain a hydrogen atom (H, D) or a halogen atom (X), which has an important function.

The hydrogen atoms (H, D) or the halogen atoms (X) contained in the i-type layer work to compensate for dangling bonds in the i-type layer, and the carrier in the i-type layer. To improve the product of the mobility and the lifetime. Also p
It has a function of compensating the interface state of each interface of the mold layer / i-type layer and the n-type layer / i-type layer, and has an effect of improving the photovoltaic power, the photocurrent, and the photoresponsiveness of the photovoltaic element. It is. The number of hydrogen atoms and / or halogen atoms contained in the i-type layer is 1 to
40 at% is mentioned as the optimum content. In particular, p
A preferable distribution form is one in which a large amount of hydrogen atoms and / or halogen atoms is distributed on each interface side of the n-type layer / i-type layer and the n-type layer / i-type layer. The preferred range of the content of atoms and / or halogen atoms is 1.1 to 2 times the content in the bulk. Further, it is preferable that the content of hydrogen atoms and / or halogen atoms is changed in accordance with the content of silicon atoms.

In the stack type photovoltaic element, the material of the pin junction i-type semiconductor layer close to the light incident side may be a material having a wide band gap, or a material far away from the light incident side.
As a material for the in-junction i-type semiconductor layer, a material having a narrow band gap is preferably used.

Amorphous silicon and amorphous silicon germanium are formed by an element for compensating for dangling bonds.
a-Si: H, a-Si: F, a-Si: H: F, a-
SiGe: H, a-SiGe: F, a-SiGe: H:
It is written as F or the like.

Further, as the characteristics of the i-type semiconductor layer suitable for the photovoltaic device of the present invention, the hydrogen atom content (C _H ) is 1.0-25.0%, AM 1.5, 100
The photoelectric conductivity (σ _p ) under mW / cm ² simulated sunlight irradiation is
1.0 × 10 ⁻⁷ S / cm or more, the dark conductivity (σ _d )
1.0 × 10 ⁻⁹ S / cm or less, Urbach Energy by Constant Photocurrent Method (CPM)
Those having a local state density of 10 ¹⁷ / cm ³ or less are preferably used.

(2) P-type semiconductor layer or n-type semiconductor layer As an amorphous material (denoted as a-) or a microcrystalline material (denoted as μc-) of a p-type semiconductor layer or an n-type semiconductor layer, For example, a-Si: H, a-Si: HX, a-S
iC: H, a-SiC: HX, a-SiGe: H, a-
SiGe: HX, a-SiGeC: H, a-SiGe
C: HX, a-SiO: H, a-SiO: HX, a-S
iN: H, a-SiN: HX, a-SiON: H, a-
SiON: HX, a-SiOCN: H, a-SiOC
N: HX, μc-Si: H, μc-Si: HX, μc −
SiC: H, μc-SiC: HX, μc-SiO: H,
μc-SiO: HX, μc-SiN: H, μc-Si
N: HX, μc-SiGeC: H, μc-SiGeC:
HX, μc-SiON: H, μc-SiON: HX, μ
c-SiOCN: H, μc-SiOCN: HX, etc.
Type valence electron controlling agents (Group III atoms B, Al,
Ga, In, Tl) or a material in which an n-type valence electron controlling agent (group V atom P, As, Sb, Bi) in the periodic table is added at a high concentration, and is referred to as a polycrystalline material (poly-). ) Is, for example, poly-Si: H, poly-Si:
HX, poly-SiC: H, poly-SiC: H
X, poly-SiO: H, poly-SiO: HX,
poly-SiN: H, poly-SiN: HX, po
ly-SiGeC: H, poly-SiGeC: HX,
poly-SiON: H, poly-SiON: HX,
poly-SiOCN: H, poly-SiOCN: H
X, poly-Si, poly-SiC, poly-S
p-type valence electron control agents (Group III atoms B, Al, Ga, In, Tl) and n-type valence electron control agents (Group V atoms P in the periodic table) for iO, poly-SiN, etc. , As, S
b, Bi) at a high concentration.

In particular, the p-type layer or the n-type layer on the light incident side includes:
A crystalline semiconductor layer with little light absorption or an amorphous semiconductor layer with a wide band gap is suitable.

The addition amount of Group III atoms of the periodic table to the p-type layer and the addition amount of Group V atoms of the periodic table to the n-type layer are 0.
The optimal amount is 1 to 50 at%.

Further, hydrogen atoms (H, D) or halogen atoms contained in the p-type layer or the n-type layer work to compensate for dangling bonds of the p-type layer or the n-type layer, and To improve the doping efficiency. The number of hydrogen atoms or halogen atoms added to the p-type layer or the n-type layer is 0.
The optimum amount is 1 to 40 at%. In particular, when the p-type layer or the n-type layer is crystalline, the optimum amount of hydrogen atoms or halogen atoms is 0.1 to 8 at%. Further, a preferred distribution form is one in which a large content of hydrogen atoms and / or halogen atoms is distributed on each interface side of the p-type layer / i-type layer and the n-type layer / i-type layer. The content of the hydrogen atom and / or the halogen atom is preferably in a range of 1.1 to 2 times the content in the bulk. Thus, the p-type layer / i-type layer and the n-type layer / i
By increasing the content of hydrogen atoms or halogen atoms near each interface of the mold layer, the defect level and mechanical strain near the interface can be reduced, and the photovoltaic power and light of the photovoltaic device of the present invention can be reduced. The current can be increased.

The electric characteristics of the p-type layer and the n-type layer of the photovoltaic element are preferably those having an activation energy of 0.2 eV or less, and those having an activation energy of 0.1 eV or less are optimal. The non-resistance is preferably 100 Ωcm or less, and most preferably 1 Ωcm or less. Further, the layer thickness of the p-type layer and the n-type layer is 1 to
50 nm is preferred, and 3 to 10 nm is optimal.

Examples of a p-type semiconductor layer or an n-type semiconductor layer using II-VI group elements include CdS and CdT.
e, ZnO, ZnSe, etc., and I-III-VI
Examples of using Group ₂ elements include CuInSe ₂ , Cu (I
nGa) Se ₂ , CuInS ₂ , CuIn (Se,
S) ₂ , CuInGaSeTe and the like.

(3) Method of Forming Semiconductor Layer In order to form a suitable group IV and group IV alloy-based amorphous semiconductor layer as a semiconductor layer of the photovoltaic device of the present invention, a preferable manufacturing method is RF This is a plasma CVD method using an alternating current or a high frequency such as a plasma CVD method or a microwave plasma CVD method.

In the microwave plasma CVD method, a material gas such as a source gas or a diluent gas is introduced into a deposition chamber (vacuum chamber) which can be decompressed, and the inside pressure of the deposition chamber is kept constant while being evacuated by a vacuum pump. The microwave oscillated by the microwave power supply is guided by a waveguide, introduced into the deposition chamber through a dielectric window (alumina ceramics or the like), and generated by decomposing a material gas plasma,
This is a method for forming a desired deposited film on a substrate placed in a deposition chamber, and can form a deposited film applicable to a photovoltaic device under a wide range of deposition conditions.

When the semiconductor layer for a photovoltaic device of the present invention is deposited by microwave plasma CVD, the substrate temperature in the deposition chamber is 100 to 450 ° C., and the internal pressure is 0.5 to 30 m.
Torr, microwave power is 0.01 to 1 W / c
m ³ and the frequency of the microwave are preferably in the range of 0.1 to 10 GHz.

When the deposition is performed by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350 ° C., the internal pressure is 0.1 to 10 Torr, and the RF power is 0.001 to 5.
Suitable conditions are 0 W / cm ³ and a deposition rate of 0.1 to 30 ° / sec.

The source gas suitable for depositing the group IV and group IV alloy-based amorphous semiconductor layer suitable for the photovoltaic device of the present invention includes a gasizable compound containing silicon atoms,
Examples include a gasizable compound containing a germanium atom, a gasizable compound containing a carbon atom, and a mixed gas of the compound.

As a gaseous compound containing a silicon atom, a chain or cyclic silane compound is used. Specifically, for example, SiH ₄ , Si ₂ H ₆ , Si
F ₄ , SiFH ₃ , SiF ₂ H ₂ , SiF ₃ H, Si ₃ H ₈ ,
SiD ₄ , SiHD ₃ , SiH ₂ D ₂ , SiH ₃ D, SiF
D ₃ , SiF ₂ D ₂ , Si ₂ D ₃ H ₃ , (SiF ₂ ) ₅ , (Si
F ₂ ) ₆ , (SiF ₂ ) ₄ , Si ₂ F ₆ , Si ₃ F ₈ , Si ₂ H ₂
F ₄ , Si ₂ H ₃ F ₃ , SiCl ₄ , (SiCl ₂ ) ₅ , Si
Br ₄ , (SiBr ₂ ) ₅ , Si ₂ Cl ₆ , SiHCl ₃ , S
Examples thereof include those in a gas state or those which can be easily gasified, such as iH ₂ Br ₂ , SiH ₂ Cl ₂ , and Si ₂ Cl ₃ F ₃ .

Specific examples of the gasifiable compound containing a germanium atom include GeH ₄ , GeD ₄ , GeF ₄ ,
GeFH ₃ , GeF ₂ H ₂ , GeF ₃ H, GeHD ₃ , Ge
H ₂ D ₂ , GeH ₃ D, Ge ₂ H ₆ , Ge ₂ D _{6 and the} like.

[0130] Examples of the element for expanding the band gap of the i-type semiconductor layer used for forming the first p-type semiconductor layer of the photovoltaic device of the present invention include carbon, oxygen, nitrogen and the like.

Specific examples of the gasizable compound containing a carbon atom include CH ₄ , CD ₄ , and C _n H _{2n + 2} (n is an integer).
C _n H _{2n (n} is an _{integer), C 2 H 2, C} 6 H 6, CO 2, CO , and the like.

As the nitrogen-containing gas, N ₂ , NH ₃ , N
D ₃ , NO, NO ₂ , and N ₂ O.

As the oxygen-containing gas, O ₂ , CO, CO ₂ ,
NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH ₃ OH and the like.

Examples of the substance introduced into the p-type layer or the n-type layer for controlling valence electrons include Group III atoms and Group III atoms in the periodic table.

Examples of the material effectively used as a starting material for introducing a group III atom include B ₂ H ₆ , B ₄ H ₁₀ , B ₅ H ₉ , and B ₅ for introducing a boron atom. H ₁₁ , B
_{6 H 10, B 6 H 12} , B 6 H 14 hydride such as boron, BF _3, B
Halogenated boron, such as Cl ₃ , may be mentioned. In addition, AlCl ₃ , GaCl ₃ , InCl ₃ , T
1Cl _{3 and the} like can also be mentioned. Particularly, B ₂ H ₆ and BF ₃ are suitable.

Effectively used as a starting material for introducing a group V atom is, specifically, PH for introducing a phosphorus atom.
₃ , hydrogenated phosphorus such as P ₂ H ₄ , PH ₄ I, PF ₃ , PF ₅ , PC
and phosphorus halides such as l ₃ , PCl ₅ , PBr ₃ , PBr ₅ and PI ₃ . In addition, AsH ₃ , AsF ₃ , AsC
l ₃ , AsBr ₃ , AsF ₅ , SbH ₃ , SbF ₃ , Sb
_{F 5, SbCl 3, SbCl 5} , BiH 3, BiCl 3, B
iBr _{3 and the} like can also be mentioned. Particularly, PH ₃ and PF ₃ are suitable.

The compounds capable of being gasified are H ₂ , H
The gas may be appropriately diluted with a gas such as e, Ne, Ar, Xe, or Kr and introduced into the deposition chamber.

In particular, a microcrystalline or polycrystalline semiconductor or a-S
When depositing a layer having a small light absorption or a wide band gap such as iC: H, the source gas is diluted 2 to 100 times with hydrogen gas, and a relatively high microwave power or RF power is introduced. Is preferred.

(Transparent electrode) The transparent electrode 107 according to the present invention
Is an electrode on the light incident side that transmits light, and also functions as an anti-reflection film by optimizing the film thickness. The transparent electrode 107 is required to have a high transmittance in a wavelength region where the semiconductor layer can absorb light and to have a low resistivity. Preferably, the transmittance at a wavelength of 550 nm or more is 80% or more, more preferably 85%.
It is desirable that this is the case. The resistivity is preferably 5 × 10 ⁻³ Ωcm or less, more preferably 1 × 10 ⁻³ Ωcm.
It is desirable that the resistivity be ⁻³ Ωcm or less. The materials include In ₂ O ₃ , SnO ₂ , and ITO (In ₂ O ₃ + Sn).
O ₂ ), ZnO, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta
A conductive oxide such as ₂ O ₅ , Bi ₂ O ₃ , MoO ₃ , Na _x WO ₃ or a mixture thereof is preferably used.
Further, an element (dopant) that changes the conductivity may be added to these compounds.

As an element (dopant) that changes the conductivity, for example, when the transparent electrode 107 is ZnO,
l, In, B, Ga, Si, F, etc .; In the case of In ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb, etc .; and in the case of SnO ₂ , F, Sb, P, As, In, T
1, Te, W, Cl, Br, I, etc. are preferably used.

As the method for forming the transparent electrode 107, various vapor deposition methods such as EB vapor deposition and sputter vapor deposition, various C
A VD method, a spray method, a spin-on method, a dipping method and the like are preferably used.

(Current Collector) The current collector 108 according to the present invention.
Is formed on a part of the transparent electrode 107 as necessary when the resistivity of the transparent electrode 107 cannot be sufficiently reduced, and serves to reduce the resistivity of the electrode and reduce the series resistance of the photovoltaic element. Examples of the material include metals such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium; alloys such as stainless steel; and conductive materials using powdered metals. Paste and the like. Then, the shape is formed in a branch shape as shown in FIG. 4, for example, so as not to block incident light on the semiconductor layer as much as possible.

Further, in the entire area of the photovoltaic device,
The area occupied by the collecting electrode is preferably 15% or less, more preferably 10% or less, and most preferably 5% or less.

Further, a pattern of the collecting electrode is formed by using a mask, and the forming method includes a vapor deposition method, a sputtering method,
A plating method, a printing method, or the like is used.

When a photovoltaic device (module or panel) having a desired output voltage and output current is manufactured using the photovoltaic device of the present invention, the photovoltaic devices of the present invention are connected in series or in series. They are connected in parallel, protective layers are formed on the front and back surfaces, and output output electrodes and the like are attached. At this time, the substrate on which the photovoltaic element is formed may be arranged on another supporting substrate. When the photovoltaic elements of the present invention are connected in series, a diode for preventing backflow may be incorporated.

[0146]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the photovoltaic element of the present invention will be described in detail by manufacturing a photovoltaic element and a photodiode made of a non-single-crystal silicon-based semiconductor material, but the present invention is not limited to these. .

(Example 1) In this example, an acid treatment method was used for etching the surface of the reflective layer, and A was used for the material of the reflective layer.
Using l, a photovoltaic device having the configuration of FIG. 1 was produced.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) It was carried out from the preparation of the substrate. Thickness 0.2
A 50 mm × 50 mm ² SUS430BA plate was ultrasonically cleaned with acetone and isopropanol and dried with hot air to completely remove the oil and fat components remaining on the substrate surface.

(2) A reflection layer was formed by a sputtering apparatus. First, an Al reflective layer was formed using a DC magnetron sputtering apparatus shown in FIG. The SUS430BA plate 502 subjected to the acid treatment was brought into close contact with the heater 503 in FIG. 5, and the deposition chamber 501 was evacuated from an exhaust port connected to an oil diffusion pump. When the pressure reached 1 × 10 ⁻⁶ , the valve 514 was opened, the mass flow controller 516 was adjusted, Ar gas was introduced at 50 sccm, and the conductance valve 513 was adjusted so that the pressure became 7 mTorr. A current is passed through the toroidal coil, and -380 V DC power is
1 was applied to the target 504 to generate Ar plasma. The target shutter 507 was opened to form a 2.5 μm-thick Al light reflecting layer on the surface of the stainless steel plate, and then the shutter was closed to extinguish the plasma and complete the production of the Al reflecting layer.

(3) The substrate surface was etched by acid treatment. The stainless steel plate on which the Al reflective layer was deposited was set on a Teflon substrate holder (not shown), and as shown in Table 1, phosphoric nitric acid (molar ratio H ₃ P
The substrate holder was arranged so that the substrate was sufficiently immersed in a container (not shown) containing acid composed of O ₄ : HNO ₃ : H ₂ O = 3: 1: 20). Next, the container containing the acid was set in an ultrasonic cleaner (not shown), and ultrasonic treatment was applied for 30 seconds to perform surface treatment.

(4) A part of the substrate having the reflective layer subjected to the etching treatment was left for evaluation (Sample 1-1), and a transparent conductive layer was formed on the other substrates.

(5) A ZnO thin film layer was formed by the same method as that for forming the reflection layer. Ar gas was introduced into the deposition chamber at 40 sccm, the substrate temperature was set to 200 ° C., the pressure was set to 5 mTorr, and a DC power of −480 V was applied from the sputtering power supply 510 to the ZnO target 508 to generate Ar plasma.

(6) The target shutter 511 was opened, and when a ZnO thin film layer having a thickness of 1.0 μm was formed on the reflective layer surface, the shutter was closed to extinguish the plasma.

(7) At the stage when the transparent conductive layer was formed, a part of the substrate was left for evaluation (Sample 1-2), and the other substrate was formed with a semiconductor layer by the following method.

(8) On the ZnO thin film layer, an n-layer, an i-layer, and a p-layer were sequentially formed by a multi-chamber separation type deposition apparatus shown in FIG. a
-Si layer and μc-Si p layer are RF
The i-layer formed by PCVD and made of a-Si is RFPC
It was formed by the VD method and the MWPCVD method. The production procedure was performed as follows.

(8-1) All transport systems and deposition chambers
^A vacuum was drawn on a ^-6 Torr table. The substrate was set on the substrate holder 690 and placed in the load lock chamber 601. The load lock chamber was evacuated to a vacuum of the order of 10 ^-3 Torr with a mechanical booster pump / rotary pump (not shown), and switched to a turbo molecular pump to evacuate the pressure to the order of 10 ^-6 Torr. The gate valve 606 was opened, and the substrate holder 690 was transferred to the n-type layer transfer chamber 602. The gate valve 606 is closed. The substrate was moved under the heater 610 for substrate heating, and hydrogen gas was flowed to make the pressure substantially the same as the pressure at the time of film formation. The substrate was heated to the temperature shown in Table 1 by the heater 610 for substrate heating and stabilized. Mass flow controller 63
6-639, stop valves 630-634, 641-
At 644, the source gases shown in Table 1 for n-type layer deposition were supplied to the deposition chamber. The RF power shown in Table 1 was supplied from the RF power supply 622 to the RF introduction cup 620. An n-type layer having a thickness shown in Table 1 was deposited for a desired deposition time.

(8-2) The supply of the source gas for n-type layer deposition was stopped, and the gas was evacuated to a degree of vacuum of the order of 10 ^-6 Torr by a turbo molecular pump. The substrate heating heater 610 is raised, the gate valve 607 is opened, and the substrate holder is set to the MW-i.
Alternatively, it has moved to the RF-i transfer chamber 603. Gate valve 607 was closed. The substrate was conveyed under the heater 611 for substrate heating, the heater 611 for substrate heating was lowered, and the substrate was heated to the substrate temperature shown in Table 1 and stabilized. RF-i
Layers were deposited. The RF-i layer is deposited in the deposition chamber 618 by MW-i.
Alternatively, a gas supply facility for RF-i layer deposition (gas supply pipe 64
9, stop valves 650-655, 661-665,
Mass flow controllers 656-660) to RF-
Source gases shown in Table 1 for i-layer deposition were supplied. RF-i
It was adjusted with an exhaust pump so that the degree of vacuum shown in Table 1 for layer deposition was obtained. A desired RF power was introduced from an RF power supply (not shown) to the bias application electrode 628, and an RF-i layer was deposited on the n-type layer to a thickness shown in Table 1 by an RF plasma CVD method.

(8-3) The supply of the raw material gas was stopped, and the inside of the deposition chamber was evacuated to a level of 10 ^-6 Torr by a turbo molecular pump. At the same time, the substrate temperature was set and maintained at a temperature shown in Table 1 suitable for the deposition of the MW-i layer. The source gas shown in Table 1 suitable for the deposition of the MW-i layer was supplied to the deposition chamber 618 from a gas supply facility for MW-i or RF-i layer deposition. The degree of vacuum in the deposition chamber was maintained at the degree shown in Table 1 by an exhaust device such as a diffusion pump (not shown). Table 1 from MW power supply not shown
Is introduced into the deposition chamber 618. At the same time, a bias power shown in Table 1 was introduced from a not-shown RF power supply to the bias electrode 628. The shutter 627 was opened and an MW-i layer was deposited on the substrate by the microwave plasma CVD method of the present invention.

(8-4) After that, the source gas shown in Table 1 suitable for the deposition of the MW-i layer is supplied from the gas supply equipment for MW-i or RF-i layer deposition to the deposition chamber 618, and the gas having a predetermined thickness is supplied. After forming the MW-i layer, the shutter was closed, the MW power and the like were stopped, and the supply of the source gas was stopped. In the deposition chamber 618,
The gas was evacuated to a level of 10 ^-6 Torr by a turbo molecular pump. In the same manner as the deposition of the RF-i layer, the RF-i
An i-layer was deposited under the conditions shown in Table 1.

(8-5) 10 ⁻⁶ T after Deposition of RF-i Layer
The deposition chamber was evacuated to the orr level. Substrate heating heater 6
11 was separated from the substrate, the gate valve 608 was opened, and the substrate holder 690 was moved to the p-type layer transfer chamber 604. The gate valve 608 was closed, the substrate was moved under the heater 612 for substrate heating, and the substrate temperature was set to the substrate temperature shown in Table 1 and stabilized. The p-type layer deposition gas was supplied to the deposition chamber 619 from the p-type layer deposition gas supply equipment (stop valves 670 to 674, 681 to 684, mass flow controllers 676 to 679). The degree of vacuum in the deposition chamber was adjusted to a degree shown in Table 1 by an exhaust pump (not shown). Table 1 from RF power supply 623 to RF introduction cup 621
Was applied, and a p-type layer was deposited to a thickness shown in Table 1 by an RF plasma CVD method. Pin as above
The structure is formed on a substrate.

(9) Next, the flow of gas is stopped, and for 5 minutes,
After continuing the flow of the H ₂ gas, the flow of the H ₂ gas was stopped, the inside of the deposition chamber and the inside of the gas pipe were evacuated to 1 × 10 ⁻⁵ Torr, and the substrate was moved to the unload chamber 605. After sufficiently cooling the substrate, it was taken out.

(10) Next, ITO shown in Table 1 was vacuum-deposited on the p-layer as a transparent electrode by resistance heating vacuum deposition. Then, a mask having a comb-shaped hole was placed on the transparent electrode, and as shown in Table 1, a comb-shaped current collecting electrode made of Cr / Ag / Cr was vacuum-deposited by an electron beam vacuum deposition method.

The fabrication of the photovoltaic device having the structure shown in FIG. 1 has been completed. This photovoltaic element was called (actual 1).

[0165]

[Table 1]

(Comparative Example 1-1) The present example is different from Example 1 in that the time of the acid treatment with ultrasonic waves was 1 second when the surface treatment of the reflective layer was performed.

The other conditions were the same as in Example 1, and samples (sample ratio 1-1), (sample ratio 1-4) and a photovoltaic element (ratio 1-1) were produced.

(Comparative Example 1-2) This example is different from Example 1 in that the temperature of the acid treatment by ultrasonic waves was set to 80 ° C. when the surface treatment of the reflective layer was performed.

The other conditions were the same as in Example 1, and samples (sample ratio 1-2), (sample ratio 1-5) and photovoltaic elements (ratio 1-1) were produced.

(Comparative Example 1-3) This example is different from Example 1 in that the time of the acid treatment with ultrasonic waves was set to 20 minutes when the surface treatment of the reflective layer was performed.

The other conditions were the same as in Example 1, and samples (sample ratio 1-3), (sample ratio 1-6) and photovoltaic elements (ratio 1-1) were produced.

Hereinafter, Example 1 and Comparative Example 1 described above will be described.
1, the reflective layers subjected to the surface treatment in Comparative Examples 1-2 and 1-3, that is, (Sample 1-1), (Sample ratio 1-1), (Sample ratio 1-2), (Sample Ratio 1
The results of the evaluation of (-3) will be described. First, the surface shape was observed with an electron microscope (SEM), and the crystal grain size was examined. In addition, the roughness of the substrate surface (maximum peak-to-peak value, hereinafter referred to as “Rmax”)
And the difference between the Rmax of the polycrystalline grains having the texture structure and the Rmax of the flat polycrystalline grains (referred to as Rmax (difference)) was determined. From these results, the schematic shape of the cross section of the reflective layer was examined.

Table 2 shows the results.

[0174]

[Table 2]

An SEM image of (Sample 1-1) is as shown in FIG. 3, and the surface is divided into a portion having irregularities and a flat portion for each crystal grain. While there is a difference in Rmax, (sample ratio 1−
In (1), the crystal grains are flat as a whole and there is no difference in Rmax. In (sample ratio 1-2) and (sample ratio 1-3), a pyramid-shaped uneven structure is obtained as a whole.
There was no difference in max.

In the following, the above-mentioned Example 1 and Comparative Example 1-
1, the substrates prepared up to the transparent conductive layer in Comparative Examples 1-2 and 1-3, that is, (Sample Actual 1-2), (Sample Ratio 1-4), (Sample Ratio 1-5), (Sample Ratio) The result of evaluating the ratio 1-6) will be described. First,
The surface shape was observed with an electron microscope (SEM), and the ZnO crystal grain size was examined. Further, the total reflectance and the irregular reflectance were obtained for each sample using a spectrophotometer equipped with an integrating sphere.

The results are shown in Table 3.

[0178]

[Table 3]

In (Sample 1-1), as shown in Table 3, the crystal grain size of ZnO forming the transparent conductive layer was large and both total reflectance / diffuse reflectance were excellent. In 4), the crystal grain size was small and the diffuse reflectance was low, and in (sample ratio 1-5) and (sample ratio 1-6), both the total reflectance and the diffuse reflectance were extremely low.

Hereinafter, Example 1 and Comparative Example 1 will be described.
1, the photovoltaic elements manufactured in Comparative Examples 1-2 and 1-3, ie, (actual-1), (ratio 1-1), (ratio 1-
The results evaluated for (2) and (ratio 1-3) will be described. First, three photovoltaic elements were manufactured, and all the photovoltaic elements were further divided into 25 subcells. Then, the shunt resistance was measured in a dark place with a reverse bias voltage of -1.0 V applied. The reference value of the shunt resistor is 4 × 10 ⁴
Ωcm ² and the yield was examined. Subsequently, an adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident optical power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were measured.

In the adhesion test, the photovoltaic elements produced by the cross-cut tape method were laid out in a grid at intervals of 1 mm.
Make 0 incisions and 100 squares.
The cellophane adhesive tape was adhered, and after sufficiently adhered, it was instantaneously peeled off, and the area of the peeled portion was evaluated.

The measurement of the initial photoelectric conversion efficiency can be obtained by installing the produced photovoltaic element under irradiation of AM-1.5 (100 mW / cm ² ) light and measuring the VI characteristics.

The photodeterioration was measured by measuring the initial photoelectric conversion efficiency of a photovoltaic element at a humidity of 50% and a temperature of 25%.
C. environment, and the rate of decrease in photoelectric conversion efficiency under AM1.5 light irradiation (photoelectric conversion efficiency after light degradation test / initial photoelectric conversion efficiency) after 500 hours of AM-1.5 light irradiation. went.

The measurement of the reverse bias (HHRB) at high temperature and high humidity was performed by installing a photovoltaic element whose initial photoelectric conversion efficiency was measured in advance in a dark place at a temperature of 85 ° C. and a humidity of 85%, and applying the photovoltaic element to the photovoltaic element. Apply a reverse bias of 0.7 V and hold for 100 hours,
Reduction rate of photoelectric conversion efficiency under subsequent AM1.5 light irradiation (photoelectric conversion efficiency after vibration degradation test / initial photoelectric conversion efficiency)
Was performed.

The measurement of the temperature / humidity deterioration was performed by measuring the initial photoelectric conversion efficiency of a photovoltaic element at a temperature of 85 ° C. and a humidity of 8 ° C.
This cycle was repeated 100 times in a dark place of 5% and maintained for 30 minutes, then lowered to a temperature of −20 ° C. for about 70 minutes and maintained for 30 minutes, and returned to 85 ° C. and 85% humidity again for 70 minutes. Rate of decrease in photoelectric conversion efficiency under AM1.5 light irradiation (photoelectric conversion efficiency after vibration degradation test /
(Initial photoelectric conversion efficiency).

The results are shown in Table 4.

[0187]

[Table 4]

As a result of the measurement, the ratio (1-
1) was low in yield and adhesion. Although the photoelectric conversion efficiency after each deterioration test is also inferior, these differences are mainly due to the FF due to the decrease in series resistance caused by adhesion.
Is the cause. For (actual-1), (ratio 1-
2) and (ratio 1-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
1) is a conventional photovoltaic element (ratio 1-1), (ratio 1-
2) It was found to have characteristics superior to (ratio 1-3).

Example 2 In this example, a photovoltaic element having the structure shown in FIG. 1 was manufactured by using RF sputtering as an etching treatment on the surface of a reflective layer and using AlSi as a material for the reflective layer.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) SUS430-2 as in the first embodiment
After the oil and fat components on the B plate were completely removed, AlSi was removed under the conditions shown in Table 5 using the sputtering apparatus shown in FIG.
A reflection layer was formed.

(2) Next, in order to perform an etching process on the surface of the reflection layer, the substrate 5 is supplied to the heater 503 shown in FIG.
02, and the processing chamber 501 was evacuated from the exhaust port. When the pressure became 1 × 10 ⁻⁶ , the valve 514 was opened, and the mass flow controller 516 was adjusted to adjust Ar
Gas was introduced at 100 sccm, and the pressure was adjusted with a conductance valve 513 so as to be 10 mTorr. RF power of 150 W was applied to the substrate from a sputtering power supply 506 to generate Ar plasma. After maintaining the Ar plasma for 15 minutes, the plasma was extinguished, and the etching process was completed.

(3) A part of the substrate subjected to the etching treatment was left for evaluation (Sample 2-1), and the other substrates were coated with the ZnO transparent electrode layer under the conditions shown in Table 5 in the same manner as in Example 1. Then, a part of the substrate was left for evaluation (Sample 2-2), and the other substrate was formed with a CVD apparatus under the conditions shown in Table 5 to form a pin-type semiconductor layer, an In ₂ O ₃ transparent electrode, and a current collecting electrode. Thus, a photovoltaic element was manufactured (Example-2).

[0195]

[Table 5]

(Comparative Example 2-1) In this example, when performing the surface treatment of the substrate, the processing time by RF sputtering was set to 5 hours.
The second example is different from the second example.

The other points were the same as in Example 2, and samples (sample ratio 2-1), (sample ratio 2-4) and photovoltaic elements (ratio 2-1) were produced.

(Comparative Example 2-2) In the present example, the point that the substrate temperature was set to 250 ° C. when performing the surface treatment of the substrate was obtained in Example 2.
And different.

The other conditions were the same as in Example 2, and samples (sample ratio 2-2), (sample ratio 2-5) and photovoltaic elements (ratio 2-2) were produced.

(Comparative Example 2-3) In this example, when performing the surface treatment of the substrate, the processing time by RF sputtering was set to 6 hours.
The difference from Example 2 is that the time is set to 0 minutes.

The other conditions were the same as in Example 2, and samples (sample ratio 2-3), (sample ratio 2-6) and photovoltaic elements (ratio 2-3) were produced.

In the following, the reflective layer subjected to the surface treatment in the same manner as in Example 1, ie, (Sample 2-1), (Sample ratio 2-1), (Sample ratio 2-2), (Sample ratio 2- The result of evaluating 3) will be described. In the same manner as in Example 1, the surface shape was observed, and the difference between the crystal grain size, the roughness of the substrate surface (maximum peak to peak value, hereinafter “Rmax”) and Rmax (referred to as Rmax (difference)), and the reflection layer The schematic shape of the cross section was examined.

The results are shown in Table 6.

[0204]

[Table 6]

In the same manner as in Example 1 (Sample Sample 2-1), the surface is divided into irregular portions and flat portions for each crystal grain as shown in Table 6; While there is a difference in Rmax, (sample ratio 1−
In (1), the crystal grains are flat as a whole and there is no difference in Rmax. In (sample ratio 1-2) and (sample ratio 1-3), a pyramid-shaped uneven structure is obtained as a whole.
There was no difference in max.

Hereinafter, the second embodiment and the second comparative example will be described.
1, the substrates prepared up to the transparent conductive layer in Comparative Examples 2-2 and 2-3, that is, (Sample Actual 2-2), (Sample Ratio 2-4), (Sample Ratio 2-5), (Sample Ratio) The result of evaluating the ratio 2-6) will be described. Each surface shape was observed, the ZnO crystal grain size was examined, and the total reflectance and diffuse reflectance were determined using a spectrophotometer equipped with an integrating sphere.

The results are shown in Table 7.

[0208]

[Table 7]

In the same manner as in Example 1 (Sample Sample 2-2), as shown in Table 7, the crystal grain size of ZnO forming the transparent conductive layer is large, and both the total reflectance / diffuse reflectance are excellent. , (Sample ratio 2-4), the crystal grain size was small and the irregular reflectance was low, (sample ratio 2-5), (sample ratio 2
In the case of 6), those having an exposed base were particularly low in both the total reflectance and the irregular reflectance.

Hereinafter, Example 2 and Comparative Example 2 will be described.
1, the photovoltaic elements produced in Comparative Examples 2-2 and 2-3, ie, (actual-2), (ratio 2-1), (ratio 2-
The results evaluated for (2) and (ratio 2-3) will be described. First, three shunt resistors were manufactured, and the shunt resistance was measured while a reverse bias voltage of -1.0 V was applied in a dark place after subdividing into 25 subcells. The reference value of the shunt resistance was set to 4 × 10 ⁴ Ωcm ² , and the yield was examined. Further, in the same manner as in Example 1, an adhesion test, measurement of initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were performed.

The results are shown in Table 8.

[0212]

[Table 8]

As a result of the measurement, the ratio (2-
1) was low in yield and adhesion. Although the photoelectric conversion efficiency after each deterioration test is also inferior, these differences are mainly due to the FF due to the decrease in series resistance caused by adhesion.
Is the cause. (Comparative 2)
In 2) and (ratio 2-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual-
2) are conventional photovoltaic elements (ratio 2-1), (ratio 2-
2) and (ratio 2-3) were found to have better characteristics.

Example 3 In this example, a photovoltaic element having the structure shown in FIG. 1 was formed by using a dry etching method using an etching gas as an etching treatment on the surface of a reflective layer and using AlSi as a material for the reflective layer. Was produced under the conditions shown in Table 9.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) US430-2D as in Example 1
After the oil and fat components on the plate were completely removed, an AlSi reflection layer was formed under the conditions shown in Table 9 using a sputtering apparatus shown in FIG.

(2) Next, the substrate 522 was brought into close contact with the substrate holder 521 shown in FIG. 5B in order to perform an etching process on the surface of the reflection layer, and the processing chamber 520 was evacuated from the exhaust port. When the air has been sufficiently evacuated, valves 527, 5
28, open the mass flow controllers 532, 533
Was adjusted to introduce CCl ₄ and Cl ₂ gas at 20 sccm,
The pressure was adjusted by the conductance valve 523 so that the pressure became 0.3 Torr. 200W from sputtering power supply 526
Was applied to the electrode 525 to generate plasma. After maintaining the plasma for 5 minutes, the plasma was extinguished and the etching process was completed.

(3) A part of the substrate subjected to the etching treatment was left for evaluation (Sample 3-1), and the other substrates were coated with the ZnO transparent electrode layer under the conditions shown in Table 9 in the same manner as in Example 1. Then, a part of the substrate is left for evaluation (Sample 3-2), and the other substrate is formed with a CVD device under the conditions shown in Table 9 to form a pin-type semiconductor layer, an In ₂ O ₃ transparent electrode, and a current collecting electrode. Then, a photovoltaic element was prepared (actual-3).

[0220]

[Table 9]

(Comparative Example 3-1) The present example is different from Example 3 in that the surface treatment of the reflective layer was performed with an etching gas of 3 seconds.

The other conditions were the same as in Example 3, except that the samples (sample ratio 3-1), (sample ratio 3-5), (sample ratio 3-9) and the photovoltaic element (ratio 3-1) were used. Was prepared.

(Comparative Example 3-2) This example is different from Example 3 in that the substrate temperature was set to 150 ° C. during the surface treatment of the reflective layer.
And different.

The other conditions were the same as in Example 3, except that the samples (sample ratio 3-2), (sample ratio 3-6), (sample ratio 3-10) and the photovoltaic element (ratio 3-2) Was prepared.

(Comparative Example 3-3) In this example, when the surface treatment of the reflective layer was performed, the processing time with the etching gas was reduced by 15 hours.
The third embodiment is different from the third embodiment.

The other conditions were the same as in Example 3, except that the samples (sample ratio 3-3), (sample ratio 3-7), (sample ratio 3-11) and the photovoltaic element (ratio 3-3) Was prepared.

In the following, the reflective layer subjected to the surface treatment in the same manner as in Example 1, ie, (Sample ratio 3-1), (Sample ratio 3-1), (Sample ratio 3-2), (Sample ratio 3-2) The result of evaluating 3) will be described. Each surface shape was observed, and the crystal grain size and the roughness of the reflective layer surface (maximum peak-to-peak value, hereinafter "Rmax") were used to determine
(Referred to as Rmax (difference)), and the schematic shape of the cross section of the reflective layer.

The results are shown in Table 10.

[0229]

[Table 10]

In the same manner as in Example 1 (Sample Sample 3-1), the surface is divided into uneven portions and flat portions for each crystal grain as shown in Table 10, and the surface is divided into uneven portions and flat portions. While there is a difference in Rmax, (sample ratio 3-
In (1), the crystal grains are generally flat and there is no difference in Rmax. In (sample ratio 3-2) and (sample ratio 3-3), the entire structure has a pyramid-shaped uneven structure.
There was no difference in max.

Hereinafter, Example 3 and Comparative Example 3 will be described.
1, the substrates prepared up to the transparent conductive layer in Comparative Examples 3-2 and 3-3, that is, (Sample 3-2), (Sample ratio 3-4), (Sample ratio 3-5), (Sample The result of evaluating the ratio 3-6) will be described. First,
Each surface shape was observed, and the ZnO crystal grain size, total reflectance, and irregular reflectance were determined.

The results are shown in Table 11.

[0233]

[Table 11]

In the same manner as in Example 1 (Sample Sample 3-2), as shown in Table 11, the crystal grain size of ZnO forming the transparent conductive layer was large, and both total reflectance / diffuse reflectance were excellent. , (Sample ratio 3-4), the crystal grain size was small, the diffuse reflectance was low, (sample ratio 3-5), (sample ratio 3
In the case of -6), the pyramid-shaped reflection layer and the transparent conductive layer reacted at the interface, and both the total reflectance and the irregular reflectance were extremely low.

Hereinafter, Example 3 and Comparative Example 3 will be described.
1, the photovoltaic elements produced in Comparative Examples 3-2 and 3-3, ie, (actual-3), (ratio 3-1), (ratio 3-
The results evaluated for (2) and (ratio 3-3) will be described. First, three cells were manufactured, and the cells were further divided into 25 subcells, and the yield was examined. Example 1
In the same manner as described above, adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident optical power), photodegradation, high temperature and high humidity reverse bias (HHR)
B) Deterioration and temperature / humidity deterioration were measured.

The results are shown in Table 12.

[0237]

[Table 12]

As a result of the measurement, (Comparative 3-
1) and (Comparative 3-2) were low in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. In (Comparative 3-3) and (Comparative 3-4), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all lower values than (Result-3). The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
3) is a conventional photovoltaic element (Comparative 3-1), (Comparative 3-
2) It was found to have characteristics superior to (comparative 3-3).

(Example 4) In this example, as in Example 3, an acid treatment method was used for etching the surface of the reflective layer.
A photovoltaic device having the configuration shown in FIG. 1 was manufactured using Ag as the material of the reflective layer.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) SUS430-2 as in the third embodiment
After forming an Ag reflective layer on the B plate under the conditions shown in Table 13, the surface of the reflective layer was etched using an acid.

(2) A part of the substrate subjected to the etching treatment was evaluated (Sample 4-1), and then a ZnO transparent electrode layer was formed under the conditions shown in Table 13 in the same manner as in Example 3 to obtain a substrate. The part was left for evaluation (Sample 4-2).

(3) Other substrates were the same as in Example 3 except that the pin type semiconductor layer, the In ₂ O ₃ transparent electrode,
A current collecting electrode was formed to produce a photovoltaic element (actual-4).

[0245]

[Table 13]

(Comparative Example 4-1) In this example, when depositing the transparent conductive layer, the substrate temperature was set to room temperature and the deposited film thickness was set to 10 μm.
m is different from that of the fourth embodiment.

The other conditions were the same as in Example 4, and samples (sample ratio 4-1), (sample ratio 4-4) and a photovoltaic element (ratio 4-1) were produced.

(Comparative Example 4-2) In this example, when depositing a transparent conductive layer, the substrate temperature was set to 500 ° C. and the deposited film thickness was set to 5
μm is different from the fourth embodiment.

The other conditions were the same as in Example 4, and samples (sample ratio 4-2), (sample ratio 4-5) and photovoltaic elements (ratio 4-2) were produced.

(Comparative Example 4-3) This example is different from Example 4 in that the surface treatment of the reflective layer by RF sputtering was performed for 60 minutes.

The other conditions were the same as in Example 4, and samples (sample ratio 4-3), (sample ratio 4-6) and photovoltaic elements (ratio 4-3) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 3, ie, (sample actual 4-1), (sample ratio 4-1), (sample ratio 4-2), (sample ratio 4
The results of the evaluation of (-3) will be described. Observation of the surface shape was performed, and the crystal grain size and substrate surface roughness (Rma
x), the difference of Rmax (Rmax (difference)) was determined, and the schematic shape of the substrate cross section (referred to as a schematic surface shape (base)) was examined. In each sample, the outline of the cross section of the substrate after formation of the transparent conductive layer (referred to as the outline surface shape (transparent)) was observed at exactly the same place where the surface of the substrate was observed with an electron microscope.

The results are shown in Table 14.

[0254]

[Table 14]

In the same manner as in Example 1 (Sample 4-1), the surface is divided into a portion having irregularities and a flat portion for each crystal grain as shown in Table 14, and the shape of the transparent conductive layer is determined by etching. The difference in Rmax between the uneven portion and the flat portion is reflected by reflecting the step difference on the substrate surface that has been performed as it is (sample ratio 4-1), (sample ratio 4
In -2), the substrate is divided into a portion having irregularities and a flat portion for each crystal grain, but the shape is not reflected on the transparent conductive layer. , And there was no difference in Rmax.

In the following, the above-described Example 4 and Comparative Example 4-
1. Substrates manufactured up to the transparent conductive layer in Comparative Examples 4-2 and 4-3, that is, (Sample Actual 4-2), (Sample Ratio 4-4), (Sample Ratio 4-5), (Sample Ratio) The result of evaluating the ratio 4-6) will be described. First,
Each surface shape was observed, and the ZnO crystal grain size, total reflectance, and irregular reflectance were determined.

The results are shown in Table 15.

[0258]

[Table 15]

In the same manner as in Example 3 (Sample Sample 4-2), the crystal grain size of ZnO forming the transparent conductive layer was large and both total reflectance / diffuse reflectance were excellent. In -4), the crystal grain size was small and the irregular reflectance was low,
In (sample ratio 4-5) and (sample ratio 4-6), both the total reflectance and the irregular reflectance were very low.

In the following, the above-described Example 4 and Comparative Example 4-
1, the photovoltaic elements manufactured in Comparative Examples 4-2 and 4-3, ie, (actual-4), (ratio 4-1), (ratio-4)
The results evaluated for (2) and (ratio 4-3) will be described. First, three cells were manufactured, and the cells were further divided into 25 subcells. The yield was examined, and the adhesion test, initial photoelectric conversion efficiency (photovoltaic power / incident optical power), light Degradation, high temperature and high humidity reverse bias (HHRB)
The deterioration and the temperature / humidity deterioration were measured.

The results are shown in Table 16.

[0262]

[Table 16]

As a result of the measurement, (comparative 4-
1) was low in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Actual-4)
In 2) and (comparison 4-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
4) is a conventional photovoltaic element (ratio 4-1),
2) It was found to have characteristics superior to (comparative 4-3).

Example 5 In this example, as in Example 4, an RF sputtering method was used for etching the surface of the reflective layer, and Cu was used for the material of the reflective layer. A power element was manufactured.

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) US430-2B as in Example 4
An etching treatment of the substrate surface was performed on the plate using an acid shown in Table 17. A part of the substrate subjected to the etching treatment was evaluated (Sample 5-1).

(2) Thereafter, a Cu reflection layer was formed under the conditions shown in Table 17 in the same manner as in Example 4. After forming the Cu reflection layer, a ZnO transparent electrode layer was formed under the conditions shown in Table 17, and a part of the substrate was left for evaluation (sample 5).
2).

(3) The other substrates were the same as in Example 4 under the conditions shown in Table 9, except that the pin type semiconductor layer, the In ₂ O ₃ transparent electrode,
A current collecting electrode was formed to produce a photovoltaic element (actual-5).

A part of the photovoltaic element was left for sample evaluation.

[0271]

[Table 17]

(Comparative Example 5-1) In this example, the point that the thickness of the deposited film was set to 10 μm when depositing the transparent conductive layer was described in Example 5.
And different.

The other conditions were the same as in Example 5, and samples (sample ratio 5-1), (sample ratio 5-4), and a photovoltaic element (ratio 5-1) were produced.

(Comparative Example 5-2) In this example, when depositing the transparent conductive layer, the substrate temperature was set to 500 ° C. and the deposited film thickness was set to 5
The difference from Example 5 is that it was set to μm.

The other conditions were the same as in Example 5, and samples (sample ratio 5-2), (sample ratio 5-5) and a photovoltaic element (ratio 5-2) were produced.

(Comparative Example 5-3) This example is different from Example 5 in that the surface treatment using an acid was performed for 20 minutes.

The other conditions were the same as in Example 5, and samples (sample ratio 5-3), (sample ratio 5-6) and a photovoltaic element (ratio 5-2) were produced.

In the following, a substrate having a reflective layer subjected to surface treatment in the same manner as in Example 4, namely,
1), (sample ratio 5-1), (sample ratio 5-2),
The result of evaluating (sample ratio 5-3) will be described. Each surface shape is observed, and the difference of Rmax (Rmax (difference)) is determined from the crystal grain size and the roughness (Rmax) of the substrate surface, and the schematic shape of the substrate cross section (referred to as the approximate surface shape (anti))
Was examined. In addition, for each sample, at the exact same place where the surface of the substrate was observed with an electron microscope, the schematic shape of the substrate cross section after forming the photovoltaic element (referred to as a schematic surface shape (primary)) was observed. .

The results are shown in Table 18.

[0280]

[Table 18]

In the same manner as in Example 1 (Sample 5-1), the surface is divided into a portion having irregularities and a flat portion for each crystal grain as shown in Table 18, and the shape on the photovoltaic element is etched. The surface of the semiconductor layer reflects the shape of the treated reflective layer as it is, and the R
While the difference of max is inherited, (sample ratio 5-
In 1), (sample ratio 5-2), and (sample ratio 5-3), the surface shape of the substrate was not reflected on the photovoltaic element, and in (sample ratio 5-1), the surface shape of the photovoltaic element was not reflected. Is relatively flat and the Rmax (difference) is small, and in (sample ratio 5-2) and (sample ratio 5-3), the Rmax (difference) is small due to the pyramid-shaped uneven structure.

In the following, Example 5 and Comparative Example 5-
1. Substrates fabricated up to the transparent conductive layer in Comparative Examples 5-2 and 5-3, that is, (Sample Actual 5-2), (Sample Ratio 5-4), (Sample Ratio 5-5), (Sample Ratio) The result of evaluating the ratio 5-6) will be described. First,
Each surface shape was observed, and the ZnO crystal grain size, total reflectance, and irregular reflectance were determined.

The results are shown in Table 19.

[0284]

[Table 19]

In the same manner as in Example 4 (Sample Sample 5-2), the crystal grain size of ZnO forming the transparent conductive layer was large and both total reflectance / diffuse reflectance were excellent. -4), the crystal grain size is small (sample ratio 5-
In 5) and (sample ratio 5-6), both the total reflectance and the irregular reflectance were very low.

The following describes Example 5 and Comparative Example 5-
1, the photovoltaic elements produced in Comparative Examples 5-2 and 5-3, ie, (actual-5), (ratio 5-1), (ratio-5)
The results evaluated for (2) and (ratio 5-3) will be described. First, three cells were manufactured each, and the cells were further divided into 25 subcells. The yield was examined, and the adhesion test, the initial photoelectric conversion efficiency (photovoltaic power / incident optical power), and the light were performed in the same manner as in Example 4. Degradation, high temperature and high humidity reverse bias (HHRB)
The deterioration and the temperature / humidity deterioration were measured.

The results are shown in Table 20.

[0288]

[Table 20]

As a result of the measurement, the ratio (5-
1) and (ratio 5-3) were low in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. In (Comparative 5-2), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all lower values than (Result-5). The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
5) is a conventional photovoltaic element (ratio 5-1), (ratio 5-
2) It was found to have better characteristics than (ratio 5-3).

(Embodiment 6) In this embodiment, the deposition apparatus using the roll-to-roll method shown in FIG.
An npinpin type solar cell was manufactured.

The substrate used was a band-shaped SUS430BA sheet having a length of 100 m, a width of 30 cm and a thickness of 0.125 mm. First, the SUS430BA sheet is wound around a feeding bobbin (not shown) in a vacuum container (not shown), and a winding bobbin connected to one end is rotated to feed the SUS430BA sheet while a roll-to-roll method is used.
An AlSi reflection layer was formed under the conditions shown in (1).

Next, the R plasma on the surface of the reflection layer was irradiated with Ar plasma.
An F plasma etching process was performed.

A part of the etched reflective layer was evaluated (Sample 6-1), and the cross-sectional shape was examined (denoted as the approximate surface shape (anti)). Under the conditions shown, the AlSi reflective layer and Zn
An O transparent electrode layer is formed, a part of the substrate is left for evaluation (Sample 6-2), the cross-sectional shape is examined (generally described as surface shape (anti)), and other substrates are roll-to-roll method. The photovoltaic element was produced under the conditions shown in Table 21 by the CVD apparatus according to (Example-6).

Hereinafter, the deposition apparatus of FIG. 7 will be described.

FIG. 7A is a schematic view of a continuous photovoltaic device forming apparatus using a roll-to-roll method. This apparatus includes a substrate delivery chamber 729 and a plurality of deposition chambers 701.
713 and a substrate take-up chamber 730 are sequentially arranged, and connected between them by a separation passage 714. Each deposition chamber has an exhaust port, and the inside can be evacuated.

The belt-like substrate 740 passes through the deposition chamber and the separation passage, and is wound from the substrate delivery chamber to the substrate winding chamber. At the same time, gas can be introduced from the gas inlets of the respective deposition chambers and separation passages, and the gas can be exhausted from the respective exhaust ports to form respective layers. A halogen lamp heater 718 for heating the substrate from behind is installed in each deposition chamber, and is heated to a predetermined temperature in each deposition chamber.

FIG. 7B is a top view of the deposition chambers 701 to 713. Each deposition chamber has an inlet 715 and an exhaust port 716 for a source gas, and an RF electrode 717 or a microwave applicator 718 is attached. The source gas inlet 715 is connected to a source gas supply device (not shown). A vacuum exhaust pump (not shown) such as an oil diffusion pump or a mechanical booster pump is connected to an exhaust port of each deposition chamber, and an inlet 719 through which scavenging gas flows is provided in a separation passage 714 connected to the deposition chamber. Introduce gas.

In the deposition chambers 703 and 707, which are the deposition chambers for the MW-i layer, bias electrodes 720 are arranged, and an RF power supply (not shown) is connected as a power supply. The substrate delivery chamber has a delivery roll 721 and a guide roller 722 for applying an appropriate tension to the substrate and always keeping the substrate horizontal. The substrate take-up chamber has a take-up roll 723 and a guide roller 724.

In the following, description will be given in accordance with the manufacturing procedure.

(1) First, the SUS430BA sheet was wound around a delivery roll 721 (with an average curvature radius of 3).
0 cm), set in the substrate unloading chamber 729, pass through each deposition chamber, and wrap the end of the substrate on the substrate take-up roll 72.
3 wrapped around.

(2) The entire apparatus was evacuated by a vacuum pump, the lamp heaters in each deposition chamber were turned on, and the substrate temperature in each deposition chamber was set to a predetermined temperature.

(3) When the pressure of the entire apparatus becomes 1 mTorr or less, a scavenging gas as shown in FIG. 7A is introduced from the scavenging gas inlet 719, and the substrate is taken up while moving in the direction of the arrow in the figure. It was rolled up.

(4) Each raw material gas was flowed into each deposition chamber. At this time, the flow rate of the gas flowing into each separation passage or the pressure of each deposition chamber was adjusted so that the raw material gas flowing into each deposition chamber did not diffuse into other deposition chambers.

(5) Then, RF power or MW power and RF bias power were introduced to generate plasma.
Under the conditions shown in FIG. 1, an n1 layer is deposited as a first pin junction in the deposition chamber 701, an i1 layer is deposited in the deposition chambers 702, 703, and 704, and a p1 layer is deposited in the deposition chamber 705, and n2 is deposited as a second pin junction in the deposition chamber 706. Layer, i2 layer in deposition chambers 707, 708, 709, p2 layer in deposition chamber 710, and third pin
N3 layer in the deposition chamber 711 and i3 in the deposition chamber 712
A p3 layer was deposited in the layer and deposition chamber 713 to form a photovoltaic device consisting of a three-layer pin junction.

(6) When the winding of the substrate is completed,
All the MW power supply, RF power supply, and plasma were extinguished, and the inflow of the raw material gas and the scavenging gas was stopped. The entire device was leaked, and the take-up roll was taken out.

(7) Next, the transparent electrode 213 was formed into a three-layered pin using a reactive sputtering apparatus under the conditions shown in Table 21.
Made on the joint.

(8) Next, a layer thickness of 5 μm was formed by screen printing.
m, a carbon paste having a line width of 0.5 mm is printed, and a silver paste having a layer thickness of 10 μm and a line width of 0.5 mm is printed thereon to form a current collecting electrode.
It was cut into a size of mx 100 mm.

In the above, n using the roll-to-roll method
The manufacture of the ipnipnip type solar cell (actual-6) was completed.

[0310]

[Table 21]

(Comparative Example 6-1) This example is different from Example 6 in that the surface treatment of the reflective layer was performed by using RF sputtering for 5 seconds.

In other respects, samples (sample ratio 6-1), (sample ratio 6-4) and photovoltaic elements (ratio 6-1) were manufactured under the same conditions as in Example 6.

(Comparative Example 6-2) This example is different from Example 6 in that the RF power used for RF sputtering was set to 600 W when performing the surface treatment of the reflective layer.

In other respects, a sample (sample ratio 6-2), (sample ratio 6-5) and a photovoltaic element (ratio 6-2) were manufactured under the same conditions as in Example 6.

(Comparative Example 6-3) This example is different from Example 6 in that the substrate temperature was set to 350 ° C. when performing the surface treatment of the reflective layer.

The other conditions were the same as in Example 6, and samples (sample ratio 6-3), (sample ratio 6-6) and photovoltaic devices (ratio 6-3) were produced.

In the following, the substrates subjected to the surface treatment in the same manner as in Example 1, namely, (Sample 6-1), (Sample ratio 6-1), (Sample ratio 6-2), (Sample ratio 6-2)
The results of the evaluation of (-3) will be described. Each surface shape was observed, and the difference in Rmax (Rmax (difference)) was determined from the crystal grain size and the substrate surface roughness (maximum peak-to-peak value, hereinafter referred to as “Rmax”). Examined.

The results are shown in Table 22.

[0319]

[Table 22]

In the same manner as in Example 1 (Sample Sample 6-2), the surface is divided into irregular portions and flat portions for each crystal grain as shown in Table 22, and the surface is divided into irregular portions and flat portions. While there is a difference in Rmax, (sample ratio 6−
In (1), the crystal grains are entirely flat and there is no difference in Rmax. In (sample ratio 6-2) and (sample ratio 6-3), the entire structure has a pyramid-shaped uneven structure.
There was no difference in max.

Further, the substrates prepared up to the transparent conductive layer in the same manner as in Example 1, that is, (Sample ratio 6-2), (Sample ratio 6-4), (Sample ratio 6-5), (Sample ratio 6)
For -6), the surface shape was observed and Zn
The O crystal grain size was examined, and the total reflectance and irregular reflectance were determined.

The results are shown in Table 23.

[0323]

[Table 23]

In the same manner as in Example 1 (Sample Sample-6), as shown in Table 23, the crystal grain size of ZnO forming the transparent conductive layer was large, and both total reflectance / diffuse reflectance were excellent. In (sample ratio 6-4), the crystal grain size was small and the diffuse reflectance was low, (sample ratio 6-5), (sample ratio 6-6).
In 6), both the total reflectance and the irregular reflectance were very low.

In the following, similarly to Example 5, the above-described Example 6, Comparative Example 6-1, Comparative Example 6-2, and Comparative Example 6
The results of evaluating the photovoltaic elements manufactured in No. 3, that is, (Comparative-6), (Comparative 6-1), (Comparative 6-2) and (Comparative 6-3) will be described. First, three shunt resistors were manufactured, and a shunt resistance was measured in a dark place with a reverse bias voltage of -1.0 V applied. 4x shunt resistance reference value
The yield was determined at 10 ⁴ Ωcm ² . Further, in the same manner as in Example 1, an adhesion test, measurement of initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were performed.

The results are shown in Table 24.

[0327]

[Table 24]

As a result of the measurement, the ratio (6-
1) was low in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Comparative 6)
2) and (Comparative 6-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
6) are conventional photovoltaic elements (ratio 6-1), (ratio 6-
2) It was found to have better characteristics than (ratio 6-3).

(Example 7) In this example, as in Example 1, the surface of the reflective layer was etched using phosphoric acid nitric acetic acid, and the photovoltaic device having the configuration shown in FIG. 1 using CuAl as the material of the reflective layer was used. A power element was manufactured.

In the same manner as in Example 1, on a SUS304 substrate,
The CuAl alloy reflective layer was formed under the conditions shown in Table 25. Next, the surface of the reflective layer was etched using phosphoric acid nitrate shown in Table 25. A part of the substrate subjected to the etching treatment was evaluated (Sample 7-1), and thereafter, Example 1
Similarly, a ZnO transparent electrode layer was formed under the conditions shown in Table 25, and part of the substrate was left for evaluation (Sample 7-2).
Other substrates were pin-type semiconductor layers under the conditions shown in Table 25,
An In ₂ O ₃ transparent electrode and a current collecting electrode were formed to produce a photovoltaic element (actual-7).

Next, an n-layer made of a-Si, a p-layer made of μc-Si, and an i-layer made of poly-Si were sequentially formed on the ZnO thin film layer by a multi-chamber separation type deposition apparatus (not shown).

Hereinafter, description will be made in accordance with the manufacturing procedure.

(1) First, using the same apparatus as in Example 1, Zn
An n-layer made of a-Si was deposited on the O thin film layer.

(2) Next, H using a double tube (not shown)
Using a deposition apparatus (not shown) by the RCVD method, Table 25 was used.
An i-layer made of poly-Si was deposited under the following conditions.

(3) Further, using the same apparatus as in Example 1, a p-layer made of μc-Si was deposited.

(4) Thereafter, an In ₂ O ₃ transparent electrode and a current collecting electrode were formed under the conditions shown in Table 25 in the same manner as in Example 1 to produce a photovoltaic element (Example-7).

[0338]

[Table 25]

(Comparative Example 7-1) This example is different from Example 7 in that the surface treatment of the reflection layer was performed with a phosphoric acid acetic acid treatment time of 3 seconds.

The other conditions were the same as in Example 7, and samples (sample ratio 7-1), (sample ratio 7-4) and a photovoltaic element (ratio 7-1) were produced.

(Comparative Example 7-2) This example is different from Example 7 in that the surface temperature of the phosphoric acid acetic acid was set to 80 ° C. when performing the surface treatment of the reflection layer.

The other conditions were the same as in Example 7, and samples (sample ratio 7-2), (sample ratio 7-5) and photovoltaic elements (ratio 7-2) were produced.

(Comparative Example 7-3) This example is different from Example 7 in that the surface treatment of the reflective layer was performed with phosphoric acid acetic acid for 20 minutes.

The other conditions were the same as in Example 7, and samples (sample ratio 7-3), (sample ratio 7-6) and photovoltaic elements (ratio 7-3) were produced.

In the following, the reflective layer subjected to the surface treatment in the same manner as in Example 1, ie, (Sample 7-1), (Sample ratio 7-1), (Sample ratio 7-2), (Sample ratio 7-2)
The results of the evaluation of (-3) will be described. Observe the surface shape of each, determine the difference in Rmax (Rmax (difference)) from the crystal grain size and the surface roughness of the substrate (maximum peak-to-peak value, hereinafter "Rmax"), and examine the schematic shape of the cross section of the substrate. Was.

The results are shown in Table 26.

[0347]

[Table 26]

In the same manner as in Example 1 (Sample 7-2), as shown in Table 26, the surface is divided into irregular portions and flat portions for each crystal grain. While there is a difference in Rmax, (sample ratio 7−
In (1), the crystal grains are entirely flat and there is no difference in Rmax. In (sample ratio 7-2) and (sample ratio 7-3), the entire structure has a pyramid-shaped uneven structure.
There was no difference in max.

The substrates prepared up to the transparent conductive layer in the same manner as in Example 1, namely, (Sample 7-2), (Sample ratio 7-4), (Sample ratio 7-5), (Sample ratio 7-7)
For -6), the surface shape was observed and Zn
The O crystal grain size was examined, and the total reflectance and irregular reflectance were determined.

The results are shown in Table 27.

[0351]

[Table 27]

In the same manner as in Example 1 (Sample 7-2), as shown in Table 27, the crystal grain size of ZnO forming the transparent conductive layer was large, and both total reflectance / diffuse reflectance were excellent. , (Sample ratio 7-4), the crystal grain size was small and the diffuse reflectance was low, (sample ratio 7-5), (sample ratio 7-
In 6), both the total reflectance and the irregular reflectance were very low.

In the following, similarly to Example 5, the above-described Example 7, Comparative Example 7-1, Comparative Example 7-2, and Comparative Example 7-
The results of evaluating the photovoltaic elements manufactured in No. 3, that is, (real-7), (ratio 7-1), (ratio 7-2) and (ratio 7-3) will be described. First, each of the three cells was fabricated and then divided into 25 subcells.
The shunt resistance was measured with a reverse bias voltage of 1.0 V applied. The reference value of the shunt resistor is 4 × 10 ⁴ Ωcm ²
Then, the yield was checked. Further, in the same manner as in Example 1, an adhesion test, measurement of initial photoelectric conversion efficiency (photovoltaic power / incident light power), photodegradation, high-temperature high-humidity reverse bias (HHRB) degradation, and temperature-humidity degradation were performed.

The results are shown in Table 28.

[0355]

[Table 28]

As a result of the measurement, (comparative 7-
1) was low in yield and adhesion. Although the photoelectric conversion conversion efficiencies after each deterioration test are also inferior, these differences are mainly due to a decrease in FF due to a decrease in series resistance due to adhesion. (Comparative 7-)
In 2) and (ratio 7-3), the initial photoelectric conversion efficiency and the photoelectric conversion efficiency after each deterioration were all low values. The initial photoelectric conversion efficiency was due to a decrease in short-circuit current (Jsc) due to a decrease in total reflectance and irregular reflectance, and the photoelectric conversion efficiency after each deterioration was mainly due to a decrease in open-circuit voltage (Voc). .

As described above, the photovoltaic device of the present invention (actual
7) are conventional photovoltaic elements (ratio 7-1), (ratio 7-
2) It was found to have characteristics superior to (Comparative 7-3).

Example 8 In this example, the relationship between the average polycrystalline grain size of the reflective layer and the difference (Rmax (difference)) in the surface roughness of the reflective layer was examined. In the same manner as in Example 3, the surface of the reflective layer is etched using a dry etching apparatus, and Al, CuAl, AgAl, Ag, Cu, C
A photovoltaic device using uMg and AlSi and having the configuration shown in FIG. 1 was manufactured.

In the same manner as in Example 3, a SUS
Was formed. Next, an etching treatment shown in Table 29 was performed as a surface treatment of the reflection layer. A part of the substrate subjected to the etching treatment was evaluated (samples 8-1 to 8-1).
81) Then, as in Example 3, Z
An nO transparent electrode layer is formed, a part of the substrate is left for evaluation (Samples 8-1 to 81), and the other substrates are the same as in Example 1 under the conditions shown in Table 29, and the pin type semiconductor layer,
n ₂ O ₃ transparent electrodes, to form a collecting electrode to fabricate a photovoltaic element (real -1～81).

[0360]

[Table 29]

The surface shape of the substrate (samples 8-1 to 81) which had been subjected to the surface treatment of the reflective layer in the same manner as in Example 1 was observed, and the crystal grain size and the substrate surface roughness (Rmax) were measured.
(Rmax (difference)) and the schematic shape of the cross section of the substrate were examined.

The results are shown in Table 30.

[0363]

[Table 30]

According to Table 30, the crystal grain size of the reflection layer was 0.05.
μm to 2500 μm, the difference in the surface roughness of the reflective layer (Rmax
(Difference) was found to be in the range of 0 to 2.5 μm.

For the substrates (samples 8-1 to 81-81) fabricated up to the transparent conductive layer in the same manner as in Example 1, the surface shape was observed, the ZnO crystal grain size was checked, and the total reflectance and irregular reflectance were determined. . As a result, the crystal grain size becomes Rmax
It was found that when the (difference) was 0.01 μm or more, the cells grew to a good size. On the other hand, the total reflectance and the irregular reflectance are R
If max (difference) is smaller than 0.01 μm, the diffuse reflectance is low, and if max (difference) is larger than 1.50 μm, the total reflectance is reduced.

Suitable etching conditions (Sample 8-2)
1 to 24, 30 to 33, 39 to 42, and 48 to 51), the crystal grain size of ZnO is large, and the total reflectance / diffuse reflectance;
Both proved to be excellent.

In the same manner as in Example 1, the photovoltaic element (actual 8-
1 to 81), each was manufactured in three pieces, and further divided into 25 subcells, and the yield was examined. Further, the adhesion test, the high-temperature high-humidity reverse bias (HHRB) deterioration,
Each test of temperature and humidity deterioration was performed.

The results are shown in Tables 31 to 34.

[0369]

[Table 31]

[0370]

[Table 32]

[0371]

[Table 33]

[0372]

[Table 34]

As a result of the measurement, (Examples 8-21 to 24, 30 to
33, 39 to 42, and 48 to 51), the others had low yield and adhesion. When the crystal grain size is smaller than 0.1 μm or Rmax (difference) is smaller than 0.01 μm, the photoelectric conversion efficiency after the deterioration test is inferior, but these are mainly caused by adhesion. This is due to a decrease in FF due to a decrease in series resistance. When the crystal grain size was greater than 2000 μm or the Rmax (difference) was greater than 1.50 μm, the photoelectric conversion efficiencies after each deterioration were all low values, but this was mainly due to the open circuit voltage (Voc). Due to the decrease in

As described above, the polycrystalline substrate of the present invention has an average polycrystalline particle diameter of 0.1 μm to 2 mm and an Rmax (difference) of 0.1 μm.
It was found that the photovoltaic element having a size of from 01 μm to 1.5 μm had excellent characteristics.

(Embodiment 9) In this embodiment, a step of a polycrystalline substrate was examined. The surface of the reflective layer is etched using an acid, and Al, CuAl, AgA
A photovoltaic element having the configuration shown in FIG. 1 using 1, Ag, Cu, CuMg, and AlSi was manufactured.

In the same manner as in Example 8, on a SUS substrate, Table 35
Was formed. Next, an etching treatment shown in Table 35 was performed as a surface treatment of the reflection layer. A part of the substrate subjected to the etching treatment was evaluated, and then a ZnO transparent electrode layer was formed under the conditions shown in Table 35 in the same manner as in Example 8, and the pin-type semiconductor was completely formed in the same manner as in Example 8 under the conditions shown in Table 35. A layer, an In ₂ O ₃ transparent electrode and a current collecting electrode were formed to produce a photovoltaic device.

[0377]

[Table 35]

With respect to the substrate which had been subjected to the surface treatment in the same manner as in Example 8, the surface shape was observed, and the crystal grain size was 6.0 μm.
After selecting a substrate having m and Rmax (difference) of 0.2 μm,
The distribution of Rmax was examined. As a result, Rmax is 0.005
It was found to be in the range of 1.5 μm.

As in Example 8, these substrates were fabricated up to the photovoltaic element, the yield was examined, and the adhesion test, the high temperature / high humidity reverse bias (HHRB) deterioration, and the temperature / humidity deterioration tests were performed. Was.

The results are shown in Tables 36 to 39.

[0381]

[Table 36]

[0382]

[Table 37]

[0383]

[Table 38]

[0384]

[Table 39]

As a result of the measurement, Rmax was 0.01 to 1.00.
Those having a thickness of μm showed good results in all the tests, but those having an Rmax of 0.01 μm or less had a low yield and a low value in the photoelectric conversion efficiency after the adhesion test. These are mainly due to a decrease in series resistance caused by adhesion.
This is due to a decrease in F. When Rmax is larger than 1.00 μm, the yield and the adhesion are not so bad values, but the photoelectric conversion efficiency after other deterioration tests is significantly inferior. For these, the open circuit voltage (V
oc).

As described above, it has been found that the photovoltaic device of the present invention in which the step of the polycrystalline substrate is 0.01 μm to 1 μm has excellent characteristics.

(Embodiment 10) In this embodiment, similarly to Embodiment 9, Al, CuAl, AgAl, Ag, Cu, CuM
g, AlSi was used as a material for the reflective layer, and an etching treatment was performed with an acid to produce a photovoltaic device having the configuration shown in FIG.

As in the case of the ninth embodiment, on the SUS substrate,
Was formed. Next, an etching treatment shown in Table 40 was performed as a surface treatment of the reflection layer. A part of the substrate subjected to the etching treatment was evaluated, and then a ZnO transparent electrode layer was formed under the conditions shown in Table 40 in the same manner as in Example 9; A layer, an In ₂ O ₃ transparent electrode and a current collecting electrode were formed to produce a photovoltaic device.

[0389]

[Table 40]

The surface shape of the substrate which had been subjected to the surface treatment in the same manner as in Example 8 was observed, and the crystal grain size was 6.5 μm.
After selecting a substrate having m and Rmax (difference) of 0.3 μm,
The distribution of steps or irregularities along the polycrystalline boundaries (abbreviated as “steps”) was examined. As a result, it was found that the distribution of the steps was in the range of 0.005 to 2.5 μm.

These substrates were fabricated up to the photovoltaic element in the same manner as in Example 9, the yield was examined, and an adhesion test, a high-temperature high-humidity reverse bias (HHRB) deterioration test, and a temperature-humidity deterioration test were performed. Was.

[0392] The results are shown in Tables 41 to 44.

[0393]

[Table 41]

[0394]

[Table 42]

[0395]

[Table 43]

[0396]

[Table 44]

As a result of the measurement, the step was 0.01 to 2.00 μm.
Those with m showed good results in all the tests, but those with a step difference of 0.01 μm or less yielded low values in the photoelectric conversion efficiency after the adhesion test. These are mainly caused by a decrease in FF due to a decrease in series resistance due to adhesion. When the step is larger than 2.00 μm, the yield and adhesion are not so bad values, but the photoelectric conversion efficiency after other deterioration tests is significantly inferior. These were mainly due to a decrease in open circuit voltage (Voc).

As described above, it was found that the photovoltaic device of the present invention in which the step of the polycrystalline substrate was 0.01 μm to 2 μm had excellent characteristics.

[0399]

According to the first aspect of the present invention, there is provided a photovoltaic device in which a polycrystalline thin film is formed on a substrate and a non-single-crystal semiconductor is formed on the polycrystalline thin film. There is a difference in the flatness of the surfaces of the individual crystal grains of the crystalline thin film, and the polycrystalline thin film has a mixture of polycrystalline grains having a surface with irregularities and polycrystalline grains having a flat surface. The use of a crystalline thin film has the following effects.

First, the adhesion between the thin film laminated on the polycrystalline thin film and the polycrystalline thin film is improved as compared with the case where a conventional polycrystalline thin film having a flat surface is used. In the process, peeling between the polycrystalline thin film and the thin film laminated thereon is eliminated, and the controllability and the degree of freedom of the manufacturing process are improved, and the production yield of the photovoltaic element is improved. In addition, as a result of accelerated weather resistance tests such as a high-temperature and high-humidity cycle test and a salt water test, weather resistance was improved. Furthermore, as a result of mechanical strength tests such as a scratch test and a bending test,
Durability improved. In addition, irregular reflection on the back surface of the photovoltaic element increases due to unevenness of the surface of the polycrystalline thin film,
The long-wavelength light that could not be absorbed by the semiconductor layer was scattered, the optical path length in the semiconductor layer was extended, the short-circuit current (Jsc) of the photovoltaic element was increased, and the photoelectric conversion efficiency was improved. Also,
The series resistance of the photovoltaic element was reduced, the fill factor (FF) was improved, and the photoelectric conversion efficiency was improved.

Further, compared to the case of using a conventional polycrystalline thin film having a surface with unevenness uniformly, the leakage current of the photovoltaic element was reduced, and the yield of the photovoltaic element was improved. . Further, the open-circuit voltage (Voc) and the fill factor (FF) were improved while the short-circuit current (Jsc) of the photovoltaic element was maintained at a high value, and the photoelectric conversion efficiency was improved.

Further, when the thin film laminated on the polycrystalline thin film is also polycrystalline, the orientation of the polycrystalline thin film laminated thereon is improved, the average grain size of the polycrystal is increased, and The variation in crystal grain size was reduced. As a result, the series resistance of the photovoltaic element decreases, and the fill factor (FF)
At the same time, light scattering was further promoted and the short-circuit current (Jsc) increased.

According to the second aspect of the present invention, since the surface of the substrate has irregularities, the adhesion between the substrate and the polycrystalline thin film is improved, and the controllability and the freedom of the manufacturing process of the photovoltaic element are improved. At the same time, the production yield of the photovoltaic device was improved, and the weather resistance and durability of the photovoltaic device were improved.

According to the third aspect of the present invention, since the main material constituting the polycrystalline thin film is a metal or an alloy, the polycrystalline thin film has a function as a back electrode of the photovoltaic element. Further, it is easy to make a difference in the flatness of the surface of each crystal grain of the polycrystalline thin film. Further, it becomes easy to form polycrystals having a particle size suitable for the use of the present invention. When the substrate is a metal or an alloy, the adhesion between the substrate and the polycrystalline thin film is improved.

According to the invention of claim 4, the main material constituting the polycrystalline thin film is a metal having high reflectance from visible to infrared light, such as gold, silver, copper, aluminum and magnesium. Has the following effects.

That is, the reflectance of the back surface of the photovoltaic element was further improved, the light absorption of the semiconductor layer was increased, and the short-circuit current (Jsc) of the photovoltaic element was further improved.

Also, a polycrystalline thin film made of a metal having a high reflectance has a difference in the flatness of the surface of each of the polycrystalline grains, and a polycrystalline thin film having irregularities on the surface and a polycrystalline thin film having a flat surface. Due to the coexistence of crystal grains, the above-mentioned metal having high reflectivity hardly diffuses into the semiconductor layer or causes migration while maintaining high diffuse reflection and high short-circuit current (Jsc), and photovoltaic power The production yield of the device was significantly improved. Also, the leakage current of the photovoltaic element decreases, and the open circuit voltage (Voc) and the fill factor (F
F) improved.

[0408] The main material of the polycrystalline thin film is
Even when aluminum is used, as in the present invention, there is a difference in the flatness of the surface of the crystal grains on the aluminum surface, and polycrystal grains having irregularities on the surface and polycrystal grains having a flat surface are mixed. By doing so, while the light is scattered on the back surface, the total reflectance of the aluminum surface including the case where the transparent conductive layer is laminated does not decrease, and the semiconductor layer is formed by the high total reflectance of the aluminum surface. And the short-circuit current (Jsc) of the photovoltaic element was improved. In addition, the adhesion between aluminum and the thin film laminated on it is also improved, the flexibility and controllability of the manufacturing process are improved, the manufacturing yield is improved, and the weather resistance and durability of the photovoltaic element are improved. did.

According to the invention of claim 5, the following effects are obtained by forming a transparent conductive layer between the polycrystalline thin film and the non-single-crystal semiconductor.

That is, the combination of the polycrystalline thin film also serving as the backside reflection layer and the transparent conductive layer improves the reflectance of the backside of the photovoltaic element, especially for long-wavelength light. The optical path length in the semiconductor layer is extended, the light absorption is increased, the short-circuit current (Jsc) of the photovoltaic element is further increased, and Conversion efficiency was further improved. In addition, by improving the adhesion between the polycrystalline thin film and the transparent conductive layer, and by reducing the current flowing in the defect region of the semiconductor layer by the transparent conductive layer having an appropriate resistance value. Thus, the degree of freedom and controllability of the manufacturing process of the photovoltaic element were improved, the production yield was improved, and the weather resistance and durability of the photovoltaic element were improved. Also,
When the polycrystalline thin film has the features of claim 1, the orientation of the transparent conductive layer is improved, the average grain size of the polycrystal of the transparent conductive layer is increased, and the variation of the grain size is reduced. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

According to the invention of claim 6, the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film, and the surface of the polycrystalline thin film has irregularities. And a region having a flat surface are mixed, the following effects are obtained.

That is, by improving the adhesion between the transparent conductive layer and the semiconductor layer, the degree of freedom and controllability of the manufacturing process of the photovoltaic element are further improved, the production yield is further improved, and the The weather resistance and durability were further improved. In the case where pyramid-shaped irregularities are formed on the entire surface of the transparent conductive layer, a defective portion of the semiconductor layer is likely to be formed on a mountain portion of the pyramid, and the photovoltaic element shunts or an open voltage ( Voc) and fill factor (FF) may be reduced, but as in the present invention, the surface of the transparent conductive layer has a difference in flatness according to the polycrystalline grain boundaries of the polycrystalline thin film. , By mixing the area where the surface is uneven and the area where the surface is flat,
Light scattering at the interface between the transparent conductive layer and the semiconductor layer is promoted while maintaining a high yield of the photovoltaic element and a high open circuit voltage (Voc) and a fill factor (FF), thereby causing a short circuit. The current (Jsc) further increased.

According to the seventh aspect of the present invention, the following effects can be obtained when the polycrystalline thin film is a transparent conductive layer.

That is, even when the substrate is a translucent photovoltaic element configured to receive light from the substrate side, the light scattering on the light incident side of the photovoltaic element causes a high short-circuit current ( While maintaining Jsc), the controllability and flexibility of the manufacturing process of the photovoltaic element were improved, the production yield was improved, and the weather resistance and durability of the photovoltaic element were improved. Also,
In the case where pyramid-shaped irregularities are formed on the entire surface of the transparent conductive film, defects in the semiconductor layer are apt to occur at the peaks of the pyramid, and the photovoltaic element shunts and the open-circuit voltage (Voc) And fill factor (FF)
However, as in the present invention, the surface of the transparent conductive layer film has a difference in flatness according to the polycrystalline grain boundaries, and the surface of the polycrystalline grains having irregularities formed on the surface has Of the transparent conductive layer and the semiconductor layer while maintaining a high yield of the photovoltaic element, and maintaining a high open voltage (Voc) and a fill factor (FF) by mixing flat polycrystalline grains. Light scattering at the interface was promoted, and the short-circuit current (Jsc) was further increased.

[0415] According to the invention of claim 8, the surface of the photovoltaic element has a difference in flatness according to the polycrystalline grain boundary of the polycrystalline thin film, and irregularities are formed on the surface. The mixture of the region and the flat surface promotes scattering of light at the light incident side of the photovoltaic element, particularly at the interface between the semiconductor layer and the upper transparent electrode, and the light incident side and the back surface of the semiconductor layer. The light will be scattered on both sides, further increasing the optical path length in the semiconductor layer, increasing light absorption and short circuit current (Jsc)
Increased further.

[0416] According to the ninth aspect of the present invention, the surface of the polycrystalline thin film is provided with a step along the grain boundary of the polycrystal, or a protrusion or a depression at the grain boundary portion of the polycrystal. The adhesion between the thin film laminated on the polycrystalline thin film and the polycrystalline thin film is further improved, the degree of freedom and controllability of the manufacturing process of the photovoltaic element are further improved, and the production yield is further improved. However, the weather resistance and durability of the photovoltaic element were further improved. In addition, due to steps or irregularities in the crystal grain boundaries on the surface of the polycrystalline thin film, irregular reflection on the back surface of the photovoltaic element increases, and long-wavelength light that could not be absorbed by the semiconductor layer is scattered in the semiconductor layer. , The short-circuit current (Jsc) of the photovoltaic element further increased, and the photoelectric conversion efficiency was further improved. Further, the orientation of the thin film laminated on the polycrystalline thin film was further improved, and the average grain size of the polycrystal of the thin film was further increased. As a result, the series resistance of the photovoltaic element was reduced, and the fill factor (FF) was improved. At the same time, light scattering was further promoted, and the short-circuit current (Jsc) was increased.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing an example of a layer configuration of a photovoltaic device according to the present invention.

FIG. 2 is a schematic sectional view showing another example of the layer configuration of the photovoltaic device according to the present invention.

FIG. 3 is an example of an electron micrograph of a substrate of a photovoltaic device according to the present invention.

FIG. 4 is a schematic plan view showing a collecting electrode of the photovoltaic device according to the present invention.

FIG. 5 is a schematic sectional view showing a sputtering apparatus and a dry etching apparatus suitable for producing a substrate of a photovoltaic element according to the present invention.

FIG. 6 is a schematic sectional view showing a deposition film forming apparatus suitable for producing a photovoltaic element according to the present invention.

FIG. 7 is a schematic cross-sectional view and a plan view showing a roll-to-roll type deposited film forming apparatus suitable for producing a photovoltaic element according to the present invention.

[Explanation of symbols]

101, 201 substrate, 102, 202 back metal reflective layer, 103, 203 transparent conductive layer, 104, 204, 207, 210 n-type semiconductor layer, 105, 205, 208, 211 i-type semiconductor layer, 106, 206, 209, 212 p-type semiconductor layer, 107, 213 transparent electrode, 108, 214 current collecting electrode, 501, 520 processing chamber, 502, 522 substrate, 503, 521 heater, 504, 508 target, 506, 510, 526 power supply, 525 electrode, 507, 511 Shutter, 512, 529 Pressure gauge, 513, 523 Conductance valve, 514, 515, 524, 527, 528, 530, 5
31 supply valve, 516, 517, 532, 533 mass flow controller, 600 deposition apparatus, 601 load lock chamber, 602, 603, 604 transfer chamber, 605 unload chamber, 606, 607, 608, 609 gate valve, 610, 611, 612 Substrate heater, 613 Substrate transfer rail, 631-634, 641-644, 651-655, 6
61 to 666, 671 to 674, 681 to 684 Stop valve, 636 to 639, 656 to 660, 676 to 679 Mass flow controller, 617, 618, 619 Deposition chamber, 620, 621 electrode, 622, 623, 624 RF power supply, 628 Bias electrode, 649 gas supply pipe, 650 shutter, 701-713 deposition chamber, 714 separation passage, 715 source gas inlet, 716 exhaust port, 717 RF electrode, 718 microwave applicator, 719 scavenging gas inlet, 720 bias electrode, 721 delivery Roll, 722, 724 Guide roller, 723 Take-up roll, 729 Delivery room, 730 Take-up room.

Claims (13)

[Claims] 1. A photovoltaic device having a polycrystalline thin film and a non-single-crystal semiconductor on a substrate, wherein the polycrystalline thin film has a difference in flatness of the surface of each crystal grain of the polycrystalline thin film. A photovoltaic device, wherein polycrystalline grains having a surface with irregularities and polycrystalline grains having a flat surface are mixed on the surface of the polycrystalline thin film. 2. The photovoltaic device according to claim 1, wherein the surface of the substrate has irregularities. 3. The photovoltaic device according to claim 1, wherein a main material constituting the polycrystalline thin film is a metal or an alloy. 4. The main material constituting the polycrystalline thin film is a metal having a high reflectance from visible to infrared light, such as gold, silver, copper, aluminum, and magnesium. 4. The photovoltaic device according to any one of 3. 5. The photovoltaic device according to claim 1, wherein a transparent conductive layer is formed between said polycrystalline thin film and said non-single-crystal semiconductor. 6. The method according to claim 1, wherein the surface of the transparent conductive layer has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film. Photovoltaic element. 7. The photovoltaic device according to claim 1, wherein the polycrystalline thin film is a transparent conductive layer. 8. The photovoltaic element according to claim 1, wherein the surface of the photovoltaic element has a difference in flatness according to a polycrystalline grain boundary of the polycrystalline thin film. The photovoltaic device according to any one of the preceding claims. 9. The method according to claim 1, wherein a step along a grain boundary of the polycrystal or a protrusion or a depression is provided at a grain boundary portion of the polycrystal on the surface of the polycrystalline thin film. The photovoltaic element according to any one of the above. 10. The difference in flatness of the surface of each crystal grain of the polycrystalline thin film is from 0.01 μm to 1.
The photovoltaic device according to claim 1, wherein the photovoltaic device has a thickness of 5 μm. 11. The photovoltaic device according to claim 1, wherein the polycrystalline thin film has a polycrystalline average particle size of 0.1 μm to 2 mm. 12. The method according to claim 1, wherein the unevenness provided on the surface of the substrate is Rma.
The photovoltaic device according to claim 1, wherein x is from 0.01 μm to 1 μm. 13. The method according to claim 1, wherein a height or a depth of a step, a ridge, or a depression along a grain boundary of the polycrystal is 0.01 μm to 2 μm on a surface of the polycrystalline thin film. Item 13. The photovoltaic element according to any one of Items 1 to 12.