JP2002289888A - Substrate for solar cell and method of manufacturing the same, and the solar cell formed by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem of a defect such as chips, cracks or the like, strain and warpage being generated, when a substrate which comprises irregularities suitable for a solar cell is formed by two sand blasting operations. SOLUTION: In a sintered and molded object, which is formed of a raw- material powder as 80 to 95 wt.% of a ceramic powder formed, by mixing particles of particle size of 3 to 6 μm with particles in the particle size of 0.5 to 1 μm in an arbitrary ratio and 20 to 5 wt.% of an organic substance by a binder and which comprises a first irregular step part in an average step of 3 μm or larger, an abrasive machining operation is performed to the surface of the first irregular step part, and a second irregular step part, whose average step is set to be smaller than the thickness of the power generation layer of the solar cell formed on the substrate for the solar cell, is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell substrate having an uneven shape, a method for manufacturing the same, and a solar cell formed using the solar cell substrate.

[0002]

2. Description of the Related Art A general solar cell comprises a laminated film of a lower electrode layer, a power generation layer (for example, an amorphous silicon layer) and an upper electrode layer on a substrate made of glass, metal, resin or the like. Further, in order to increase the amount of light absorbed by the power generation layer of the solar cell, the photoelectric conversion efficiency has been improved by forming the laminated film on a substrate having an uneven surface.

[0003] The conventional structure specifically disclosed and its manufacturing method will be described below. FIG. 4 is a sectional process view showing a conventional method for manufacturing a solar cell substrate.

Japanese Patent Application Laid-Open No. 10-70294 discloses FIG.
As shown in (c), a ceramic substrate having a second uneven step 2 smaller than the first uneven step 1 on the surface of the first uneven step 1 is described. If the solar cell is formed as an upper layer using the substrate, light is scattered at the interface of the laminated film due to the shape of the first and second large and small uneven portions provided on the substrate surface, and the amorphous silicon layer is formed. It is possible to increase the optical path length in the inside, and it is possible to improve the short-circuit current and the photoelectric conversion efficiency of the solar cell.

In the above-mentioned publication, sandblasting is performed twice as a method for forming the first and second large and small uneven steps. Specifically, as shown in FIG. 4A, the surface of the smooth ceramic substrate 44 has a particle size of 50 μm.
The first sandblasting process is performed using the first abrasive grains 46 of m or more, and the average step d1 shown in FIG.
The above-mentioned first uneven step portion 1 is formed, and the particle size is 20 μm.
By performing the second sandblasting process using the following second abrasive grains 48, the average step shown in FIG.
The average step d2 is formed on the surface of the first uneven portion 1
Discloses that it is possible to obtain a ceramic substrate 44 having a solar cell forming surface 50 having a second uneven step portion 2 of 0.5 μm or less.

[0006]

However, in the prior art method, the substrate surface after the first sandblasting is damaged by the first abrasive grains 46 having a particle size of 50 μm or more, and many chips and cracks are formed. Are irregularly generated and can be processed into a relatively smooth surface by the second sandblasting process, but a solar cell substrate from which defects have been completely removed cannot be formed.

[0007] Further, in general, when blasting is performed, distortion or warpage occurs in the blasted object. Therefore, there is a problem that the degree of distortion or warping is further increased by performing sandblasting on the substrate twice.

An object of the present invention has been made in view of the above technical problems, and includes a defect such as a chip or a crack;
By providing a solar cell substrate having first and second uneven steps suitable for a solar cell that does not warp, a method of manufacturing the same, and a solar cell formed using the solar cell substrate. is there.

[0009]

Means for Solving the Problems A solar cell substrate according to the present invention is a solar cell substrate in which a second uneven step smaller than 3 μm is formed on the surface of the first uneven step of 3 μm or more. An average step formed by a raw material powder of 80 to 95 wt% ceramic powder in which particles having a diameter of 3 to 6 μm and particles having a particle size of 0.5 to 1 μm are mixed at an arbitrary ratio and an organic binder of 20 to 5 wt% The surface of the first uneven step is subjected to abrasive processing on a sintered molded body having a first uneven step of 3 μm or more, and the thickness of the power generation layer of the solar cell formed on the solar cell substrate It is characterized in that a second uneven portion having a smaller average step is formed.

Further, the abrasive processing performed on the solar cell substrate of the present invention is sand blasting or liquid honing.

The method for manufacturing a solar cell substrate according to the present invention is characterized in that ceramic powder obtained by mixing particles having a particle size of 3 to 6 μm and particles having a particle size of 0.5 to 1 μm at an arbitrary ratio as raw material powder After sintering a substrate-like molded body containing 20 to 5 wt% of an organic binder with respect to 80 to 95 wt% of a raw material powder to form a sintered body having a first uneven step surface having an average step of 3 μm or more, A second uneven step portion having an average step smaller than the thickness of the power generation layer of the solar cell formed on the substrate is formed on the surface of the first uneven step portion by abrasive processing.

The solar cell according to the present invention comprises a lower electrode layer, a power generation layer,
A stacked film of an upper electrode layer is formed.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The method for manufacturing a solar cell substrate according to the present invention is directed to a method for manufacturing a solar cell substrate, comprising the steps of:
After a ceramic sintered body having the following structure, a blast process is performed only once on the surface of the first uneven step portion 1, and the second uneven step portion 2 having an average step equal to or less than the thickness of the power generation layer of the solar cell. Is formed, it is possible to minimize the defects, distortion, and warpage of the substrate caused by the conventional blast processing twice. An optimal embodiment of the first and second uneven step shapes will be described below with reference to FIG.

FIG. 3 is a cross-sectional view of an amorphous silicon solar cell formed by using the solar cell substrate according to the manufacturing method of the present invention. Solar cell 42 formed according to the present invention
The solar cell formation of the solar cell substrate 24 in which the second uneven step portion 2 having an average step not more than the thickness of the power generation layer of the solar cell is formed on the surface of the first uneven step portion 1 having an average step not less than 3 μm. On the surface 26, a metal film 28 of Al, Ag or the like as a lower electrode layer, an amorphous silicon film 38 as a power generation layer, and a transparent conductive film 40 as an upper electrode layer are sequentially laminated.
The amorphous silicon film 38 is made of amorphous silicon n
Layer (hereinafter abbreviated as n layer) 30, amorphous silicon i
This is a structure in which a layer (hereinafter abbreviated as i layer) 32, an amorphous silicon carbon buffer layer (hereinafter abbreviated as b layer) 34, and an amorphous silicon carbon p layer (hereinafter abbreviated as p layer) 36 are laminated in this order.

The second uneven step portion 2 at the interface of the laminated film has an effect of scattering light in the film, and the scattering of light is a refractive index (n).
Interface, for example, a transparent conductive film (n = 1.9)
And at the interface of the amorphous silicon film (n = 3.5)
The guided light will be scattered. The refracted light is i
Since the light is guided obliquely through the layer 32, the optical path length can be made longer than when the light is guided vertically. As a result, the amount of light absorbed by the solar cell into the i-layer 32 increases, and the short-circuit current can be increased.

If the unevenness at the interface of the laminated film is increased by setting the second unevenness step portion 2 to be large, the light scattering effect can be increased. 38 thickness (typically 0.5
μm), the metal film 2 of the upper electrode layer
8 and the transparent conductive film 40 of the lower electrode layer are likely to be short-circuited. Therefore, it is necessary that the average step of the second uneven step portion 2 is equal to or less than the thickness of the power generation layer of the solar cell.

The first uneven step portion 1 not only scatters light but also has the effect of causing the reflected light of the light once transmitted through the amorphous silicon film 38 and reflected by the lower electrode 28 to enter the amorphous silicon film again. It is a well-known fact that the effect is remarkable when the step is 3 μm or more, and it is clear from the experimental results described in the prior art (Japanese Patent Laid-Open No. 10-70294).

As is clear from the above description, the average step of the second uneven step 2 is set to be equal to or less than the thickness of the power generation layer of the solar cell, and the average step of the first uneven step 1 is set to 3 μm or more. Thus, an optimum light scattering effect can be obtained without short-circuiting the upper and lower electrode layers.

(Embodiments) Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 (a) to (c)
Is a process cross-sectional view showing a method for manufacturing a solar cell substrate of the present invention, and FIG. 3 is a schematic cross-sectional view of a solar cell using a substrate prepared according to an embodiment of the present invention.

First, a method of obtaining a ceramic sintered body having a surface having irregularities with an average step of 3 μm or less will be described with reference to a case where alumina (Al ₂ O ₃ ) is used as a ceramic raw material. In addition, magnesia (Mg
O), silica (SiO ₂ ), zirconia (ZrO ₂ ), mullite (3Al ₂ O ₃ .2SiO ₂ ), or the like, can similarly form the solar cell substrate of the present invention.

A substrate-like molded body 10 as shown in FIG. 2A was prepared from the alumina powder mixed in the above ratio.
The molded body 10 includes alumina particles 12 having a particle size of 3 to 6 μm,
70 wt% of alumina particles 14 having a particle size of 0.5 to 1 μm,
An alumina powder mixed at a ratio of 30 wt% and an organic binder 16 were kneaded together with an organic solvent, and then molded on a substrate. It is preferable that the alumina powder is formed in the range of 80 to 95 wt% and the binder 16 is formed in the range of 20 to 5 wt%, and the same applies when other ceramic raw materials are used.

Since the particle size of the alumina powder greatly affects the surface shape of the sintered body, it is important to select the particle size of the powder and to set an appropriate mixing ratio. Is done.

The alumina particles 14 having a particle size of 0.5 to 1 μm exist so as to fill gaps between the alumina particles 12 having a particle size of 3 to 6 μm, thereby reducing defects and voids in the sintered body.
To increase the density and increase the strength, FIG.
It is desirable to keep the compact 10 as close as possible to the closest packing.

The binder 16 is used to enhance the moldability, plasticity and adhesiveness during molding and to firmly bind the ceramic powder until the ceramic is fired. For example, the binder 16 is made of polymethacrylate, dibutyl phthalate or the like. Can be used.

Next, the molded body 10 was placed in an electric furnace for 2 hours.
After the binder 16 was decomposed and evaporated at around 00 to 600 ° C., it was fired at 1550 to 1650 ° C. to obtain a sintered body 18 having an average step D1 of the first uneven step portion 1 of 3 μm or more. .

Further, since the surface 20 of the sintered body 18 is formed by sintering alumina particles, the surface 20 of the substrate is subjected to sandblasting using abrasive grains having a particle diameter of 50 μm or more according to a conventional method. In addition, a substrate having a smooth surface with few cracks and defects can be formed.

Next, as shown in FIG. 2B, the surface 20 of the sintered body 18 was subjected to abrasive processing by a wet liquid honing process. In the wet liquid honing process, water containing abrasive grains is sprayed on the workpiece, so that when using small abrasive grains, the workability is good, and the grinding can be performed while washing with water. Cleaning is also easier. The conditions of the wet liquid honing treatment are as follows: alumina abrasive grains having a particle diameter of 20 μm or less are used, a projection distance is 20 mm, and a projection angle is 9 mm.
0 degree, processing speed 10 mm / sec, air pressure 0.8-1.
The ejection port was set at about ² kg / cm ^2, and the size of the injection port was set according to the size of the substrate to be processed. Similar effects can be obtained by using silicon carbide (SiC) for the alumina abrasive grains.

A similar shape can be obtained by performing the above-described abrasive grain processing by sandblasting using alumina abrasive grains 22 having a particle size of 20 μm or less.

Further, by subjecting the surface 20 of the sintered body 18 to the above-mentioned abrasive processing, a solar cell substrate 24 as shown in FIG. 2C is obtained. A second uneven step portion 2 is formed on an uneven surface having an average step of 3 μm or more, and the average step D2 is 0.5 μm.
m or less.

As described above, the solar cell substrate 24 can be formed by performing the blasting process using the small abrasive grains only once on the sintered body 18 having a smooth surface, so that the abrasive grains do not damage the substrate. As much as possible, generation of distortion and warpage is suppressed, and chipping or cracking does not occur on the solar cell forming surface 26.

On the solar cell forming surface 26 of the solar cell substrate 24 manufactured as described above, for example, as shown in FIG.
g of a metal film 28 having a thickness of 1 μm, an amorphous silicon film 38 serving as a power generation layer having a thickness of about 500 nm using a plasma CVD device, and further using ITO or SnO 2 as an upper electrode layer using a sputtering device. 80n thickness
m, the solar cell 42 was obtained. Light incident from the transparent conductive film 40 side is added to the scattering effect of the small uneven step portion 2 in addition to the scattering effect of the large uneven step portion 2, and the optical path length in the amorphous silicon film 38 increases, thereby increasing the short-circuit current. It is known that the photoelectric conversion efficiency of the solar cell can be improved.

Hereinafter, a specific method of manufacturing the power generation layer will be described. The amorphous silicon film 38 has an amorphous silicon n layer (hereinafter abbreviated as n layer) 30 having a thickness of 40 nm, an amorphous silicon i layer (hereinafter abbreviated as i layer) 32 having a thickness of 400 nm, and a b layer (amorphous silicon carbon composition change layer). Hereinafter, the layer b is abbreviated to a thickness of 15 nm, and an amorphous silicon carbon p layer (hereinafter abbreviated as a p layer) 36 is laminated to a thickness of 12 nm. The conditions for forming each layer are described below. The n layer 30 has a substrate temperature of 225 ° C. and a power of 0.05 W /
cm ² , pressure 120Pa, gas flow rate is SiH4 / PH3
(2% H2 dilution) in the order of 400/40 sccm.
The i-layer 32 has a substrate temperature of 225 ° C. and a power of 0.05 W / c.
m ² , pressure 80Pa, gas flow rate is 600sc for SiH4
cm. The b layer 34 has a substrate temperature of 225 ° C., a power of 0.02 W / cm ² , a pressure of 120 Pa, and a gas flow rate of Si.
300/300 / 300scc in the order of H ₄ / CH ₄ / H ₂
m. The p-layer 36 has a substrate temperature of 225 ° C. and a power of 0.
02W / cm ^2, pressure 120 Pa, gas flow rate SiH ₄ /
CH ₄ / B ₂ H ₆ (2% H ₂ dilution) in the order of 45/105/4
The test was performed at 5 sccm.

The characteristics of the solar cell 42 formed as described above include a short-circuit current of 47.1 μA / cm ² , an open voltage of 0.64 V, a fill factor of 0.73, and a photoelectric conversion efficiency of 15.
1% could be obtained. This characteristic is not inferior to the characteristics of a solar cell formed on a ceramic substrate for a solar cell manufactured by using the conventional technique, and the solar cell substrate according to the manufacturing method of the present invention is a ceramic substrate having irregularities. Since the blast process is performed once using small abrasive grains after forming the consolidated body, chipping and cracking caused by abrasive grain processing can be suppressed, and the problem of substrate distortion and warpage can be solved. Substrate cracking does not occur in subsequent handling.

Further, by the one blast process,
A surface shape suitable for a solar cell substrate can be realized on a ceramic substrate.

[0035]

As described above, in the solar cell substrate formed by the present invention, the surface of the first uneven step portion 1 formed at the stage of the ceramic sintered body is subjected to abrasive grain processing only once. The second uneven step portion 2 can be formed in this way, so that the effect on the solar cell due to the unevenness of the large and small steps can be maintained, without causing defects such as chipping or cracks on the substrate, and warping, distortion, and cracking. A solar cell formed using the solar cell substrate, the method of manufacturing the same, and the solar cell substrate could be provided.

The solar cell substrate of the present invention can also be applied to the production of a translucent ceramic dial for a solar cell watch that also serves as a solar cell substrate.

[Brief description of the drawings]

FIG. 1 is a structural sectional view showing a solar cell substrate according to an embodiment of the present invention.

FIG. 2 is a process cross-sectional view illustrating a method for manufacturing a solar cell substrate according to an embodiment of the present invention.

FIG. 3 is a schematic structural cross-sectional view of a solar cell configured using a solar cell substrate formed according to an embodiment of the present invention.

FIG. 4 is a process sectional view showing a conventional method for manufacturing a solar cell substrate.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 1st uneven | corrugated step part 2 2nd uneven | corrugated step part 10 Molded body 12 Alumina particles with a particle diameter of 3-6 μm 14 Alumina particles with a particle diameter of 0.5-1 μm 16 Binder 18 Sintered body 20 Sintered body surface 22 Grinding Particles 24 Solar cell substrate 26 Solar cell forming surface 28 Metal film 30 n layer 32 i layer 34 b layer 36 p layer 38 amorphous silicon film 40 transparent conductive film 42 solar cell

Claims (4)

[Claims] 1. A solar cell substrate in which a second uneven step smaller than 3 μm is formed on the surface of a first uneven step having a diameter of 3 μm or more and a particle having a particle diameter of 3 to 6 μm and a particle having a diameter of 0.5 to 0.5 μm.
80-95 wt% of 1 μm particles mixed at any ratio
And a first powder having an average level difference of 3 μm or more formed by a raw material powder of ceramic powder and an organic binder of 20 to 5 wt%.
An abrasive step is performed on the surface of the first uneven step on the sintered molded body having the uneven step of the above, and an average step smaller than the thickness of the power generation layer of the solar cell formed on the solar cell substrate. Characterized in that a second uneven step portion is formed. 2. The solar cell substrate according to claim 1, wherein the abrasive processing is sand blasting or liquid honing. 3. A particle having a particle size of 3 to 6 μm and a particle size of 0.5 to 1
A ceramic powder obtained by mixing particles of each μm in an arbitrary ratio is used as a raw material powder, and a substrate-like molded body containing 20 to 5 wt% of an organic binder with respect to 80 to 95 wt% of the raw material powder is sintered. After forming a sintered body having a first uneven step surface having a step of 3 μm or more, the thickness of the power generation layer of the solar cell formed on the substrate by abrasive processing on the surface of the first uneven step A method for manufacturing a solar cell substrate, comprising: forming a second uneven step portion having a small average step. 4. A solar cell using the solar cell substrate according to claim 1.