JPH06204541A - Photovoltaic device - Google Patents

Abstract

PURPOSE:To furnish a photovoltaic device of which the photoelectric conversion efficiency is improved. CONSTITUTION:A surface protecting layer 101 is provided in lamination on the light incidence side and at least one light-scattering layer 102 having a refractive index different from the one of the surface protecting layer and having an indented structure is formed in the surface protecting layer 101. When a light cast on a photovoltaic device is scattered by the light-scattering layer 102, according to this constitution, an optical path in a semiconductor layer 104 is prolonged substantially, a short-circuit current of the photovoltaic device is improved and the photoelectric conversion efficiency is improved. Since absorption of the light by the semiconductor layer increases, besides, the semiconductor layer can be made thin, optical deterioration of the photovoltaic device can be suppressed and the cost of manufacture can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device,
In particular, it relates to a photovoltaic device for improving the stable output characteristics by effectively utilizing incident light.

[0002]

2. Description of the Related Art In a photovoltaic device having a semiconductor layer for generating a photovoltaic power and an electrode, as a method for improving the photoelectric conversion efficiency, the light incident on the photovoltaic device is scattered to form the semiconductor layer. There is known a method of increasing the short-circuit current by substantially increasing the optical path length in the inside and thereby increasing the amount of light absorbed in the semiconductor layer.

In this case, the structure of the photovoltaic device for scattering the light incident on the photovoltaic device is one in which a transparent electrode having an uneven structure is formed on a transparent substrate such as a glass substrate, or on the substrate. Known are those provided with a light-reflecting layer having a concavo-convex structure, and further those having a concavo-convex structure formed on the surface of a semiconductor substrate.

Among these structures, the one using the glass substrate and the semiconductor substrate as the substrate scatters the light on the surface on the light incident side, and the one having the unevenness in the light reflecting layer is the light incident side. It has a structure that scatters light on the back side.

Of these, in the case of a structure in which light is scattered on the light incident side surface and a glass substrate is used, since light is incident on the semiconductor layer from the substrate side, a concavo-convex structure is formed before the semiconductor layer is formed. The transparent electrode is formed, and the concavo-convex structure is formed at a relatively high temperature of approximately 300 ° C. or higher.

[0006]

However, in the photovoltaic device of the type in which light is incident on the semiconductor layer from the side opposite to the substrate, the thin film semiconductor layer is formed on the substrate and then the light is scattered. Since the structure is formed, the substrate temperature cannot be raised to the formation temperature of the semiconductor layer or more, and it is difficult to form the transparent electrode having the uneven structure as in the case of the glass substrate.

On the other hand, in the case of a structure in which the transparent electrode also functions as an antireflection layer, the reflectance is lowered in a wide wavelength range, so that the optical thickness (nd) of the transparent electrode is λ /
It is often made as thin as about 4 (where λ is the wavelength that minimizes the reflectance). In the case of such a configuration, the transparent electrode is too thin and is not suitable for forming an uneven structure for scattering light.

Further, in the case of a structure in which a semiconductor substrate is used to form a concavo-convex structure for scattering light on the surface of the semiconductor, the semiconductor itself is processed, so delicate handling is required and the number of manufacturing steps increases. This causes a large increase in manufacturing cost.

As described above, in a photovoltaic device other than the type in which light is incident on the semiconductor layer from the substrate side using the glass substrate, it is difficult to have a structure in which light is scattered on the surface on the light incident side. Or there was a problem in terms of manufacturing cost.

However, in order to put into practical use a low-cost photovoltaic device that can be used for various purposes including general power supply, a low-cost substrate such as a stainless substrate or a synthetic resin film other than a glass substrate can be used. It has been desired to improve the photoelectric conversion efficiency of a photovoltaic device that uses, and as a result, even in a photovoltaic device that uses a low-cost substrate other than a glass substrate, light is emitted on the surface on the light incident side. A structure having a scattering structure has been desired.

The present invention has been made to solve the above-mentioned problems of the prior art, and is a photovoltaic device of the type in which light is incident on the semiconductor layer from the side opposite to the substrate, or an optical device using a semiconductor substrate. It is an object of the present invention to provide a photovoltaic device which is applied to an electromotive force device, has a structure that scatters light on the surface on the light incident side, and is capable of stably improving photoelectric conversion efficiency.

[0012]

In order to achieve the above object, the invention of claim 1 is a photovoltaic device in which a surface protective layer is laminated on a light incident side of a semiconductor layer, in which the surface protective layer is provided. Is characterized by forming at least one light-scattering layer having a refractive index different from that of the surface protective layer and having an uneven structure.

The invention of claim 2 is characterized in that, in the invention of claim 1, the light-scattering layer has a concavo-convex structure on the surface side with respect to the light incident direction.

The invention of claim 3 is characterized in that, in the invention of claim 1, the light-scattering layer has an uneven structure on the back surface side with respect to the light incident direction.

The invention of claim 4 is characterized in that, in the invention of claim 1, the light-scattering layer has a concavo-convex structure on both the front surface and the back surface in the light incident direction.

The invention of claim 5 is from claim 1 to claim 4.
In the inventions up to, the concavo-convex structure has a surface roughness Rma.
It is characterized in that the value of x lies between 0.05 μm and 100 μm.

The invention of claim 6 is from claim 1 to claim 5.
2. The light according to claim 1, wherein the difference between the refractive index of the substance forming the surface protective layer and the refractive index of the substance forming the light scattering layer is 0.1 or more. Electromotive force device.

The invention of claim 7 is from claim 1 to claim 6.
In the above inventions, a light reflection layer for light scattering is formed on the side opposite to the light incident direction with respect to the semiconductor layer.

[0019]

According to the inventions of claims 1 to 4, since the light-scattering layer having the concavo-convex structure is provided in the surface protective layer on the light-incident side, the light incident on the photovoltaic device is After being scattered in the surface protective layer, it is incident on the semiconductor layer, the optical path length in the semiconductor layer is extended, the absorption of light by the semiconductor layer is increased, and the short-circuit current is increased, which can improve the photoelectric conversion efficiency. it can.

In this case, when a plurality of the light-scattering layers having the concavo-convex structure are formed in the surface protection layer as in the fifth aspect of the invention, the scattering of incident light is further increased, and the light from the semiconductor layer is further increased. Is increased and the short-circuit current is increased, so that the photoelectric conversion efficiency of the photovoltaic device can be further improved.

According to the invention of claim 6, the difference between the refractive index of the substance forming the light scattering layer and the refractive index of the substance forming the surface protective layer is 0.1 or more. Since the scattering of incident light is increased, the absorption of light by the semiconductor layer is increased, the short-circuit current is increased, and the photoelectric conversion efficiency can be further improved.

Further, according to the invention of claim 7, the light incident on the photovoltaic device is scattered on both the incident side and the reflecting side, and the light absorption by the semiconductor layer is further increased. It is possible to realize an increase and an improvement in photoelectric conversion efficiency.

FIG. 1 shows the structure of a typical photovoltaic device according to the present invention. In the figure, 101 is a surface protection layer, 102 is a light scattering layer, 103 is a transparent electrode, 10
4 is a semiconductor layer, 105 is a collector electrode, 106 is a back electrode,
Reference numeral 107 is a substrate, and 108 is a back surface protective layer.

(Surface Protective Layer) The surface protective layer 101 is formed to protect the photovoltaic device from the external environment, and is formed on the surface of the photovoltaic device. As a material, a material having weather resistance may be appropriately selected from synthetic resins and the like. However, when it is formed on the light incident side surface, in addition to weather resistance, the transmittance of the photovoltaic device for light of a wavelength having sensitivity is preferably 80% or more, more preferably 90% or more on average, and most preferably. It is desirable that the average is 95% or more. Further, it is desirable that the transmittance does not decrease much even if it is left outdoors for a long time.

The surface protective layer 101 may be divided into an upper transparent material, a filler, and an adhesive, depending on the function.

As a concrete material of the surface protective layer 101, as the upper transparent material, a fluororesin such as glass, acrylic, polycarbonate, FRP or PVF (polyvinyl fluoride), a silicone resin or the like is preferably used. As the filler, silicone resin, PVB (polyvinyl butyral), EVA (ethylene vinyl acetate), etc. are preferably used.

The surface protective layer 101 is usually formed by degassing the film-shaped material and bonding it to a photovoltaic element, or heating the material to melt it or dissolving it in a solvent to apply it. It

Further, in the photovoltaic device of the present invention, a silicone resin, PVB (polyvinyl butyral), EVA (ethylene vinyl acetate) or the like is used in order to improve the adhesion between the light scattering layer and the surface protective layer. The most suitable material is one that can be heated and melted or dissolved in a solvent and applied.

The refractive index of the surface protective layer in the vicinity of the light scattering layer is increased by quenching the molten surface protective layer material or rapidly drying the solvent of the surface protective layer material dissolved in the solvent. be able to. It is considered that this is because stress is applied to the surface protective layer near the light scattering layer.

(Light Scattering Layer) In the present invention, the light scattering layer 1
Reference numeral 02 denotes a layered structure having a concavo-convex structure, and the light scattering layer 102 provided in the surface protective layer 101 may be a single layer or a plurality of layers. Here, the uneven structure may be provided on either the front surface side or the back surface side of the light scattering layer with respect to the light incident direction, or may be provided on both the front surface side and the back surface side.

The size of the irregularities is the maximum surface roughness Rma.
x is preferably 0.1 μm to 100 μm, more preferably 0.2 μm to 50 μm, and most preferably 0.5 μm to 10 μm.

The light scattering layer 102 is the surface protective layer 10
It may be formed at any position in the layer thickness direction in 1 from near the surface to near the transparent electrode 103. However, it is desirable not to form within 1 μm in the vicinity of the transparent electrode 103. This is because if the transparent electrode 103 also serving as an antireflection layer and the light scattering layer 102 are brought too close to each other, the antireflection condition may be impaired.

Further, the material of the light scattering layer 102 has a refractive index which is preferably 0.1 or more, more preferably 0.2 or more, and most preferably 0.3 or more, together with the refractive index of the surface protective layer 101. Is desirable. Regarding the material of the light scattering layer 102, the transmittance of light having a wavelength of 400 nm to 1000 nm is preferably 80% or more on average, and more preferably 9% on average.
It is preferably 0% or more, and optimally 95% or more on average.

In particular, since most of the materials suitable for the surface protective layer 101 have a refractive index of about 1.5, the material for the light scattering layer 102 has a refractive index of 1.0 to 1.4, or A value of 1.9 to 2.5 is desirable. Substances with a refractive index in this range are wavelengths from 400 nm to 1000
Since the transmittance of light having a wavelength of nm also satisfies the above-mentioned value, it is preferable. A material having a refractive index of more than 2.5 has a good light-scattering ability, but it is not preferable because the transmittance of light having a wavelength of 400 nm to 1000 nm cannot obtain the above value in many cases.

Further, it is desirable that the material of the light scattering layer 102 has excellent adhesion to the material of the surface protective layer 101, is chemically stable, and has a thermal expansion coefficient close to that of the material of the surface protective layer 101.

As a specific example of the material of the light scattering layer 102,
For ZnS, TiO₂, Ta₂O _Five, CeO₂, Zr
O₂, Sb₂O₃, Nd₂O₃, In₂O₃, SiC,
Si ₃N_Four, SiO, La₂O₃, SnO₂, ZnO,
CdO, Cd₂SnO_Four, ThO₂, MgO, Pb
F₂, Al₂O₃, NdF₃, LaF₃, MgF₂, L
iF, Na₃AlF₆, NaF, CaF₂Etc., or
A mixture of these compounds is preferable.

Further, among the materials of these light scattering layers, the above-mentioned material which is preferably used as the surface protective layer 101 has a refractive index of about 1.5 in many cases.
nO, ZnS, TiO ₂ , In ₂ O ₃ , SnO ₂ , Mg
F ₂ and CaF ₂ are particularly preferably used. Furthermore, these materials, silicone resin, PVB as a surface protective layer
A combination of (polyvinyl butyral) and EVA (ethylene vinyl acetate) exhibits the characteristics of excellent adhesion and chemical stability, and is therefore most preferably used.

As a method of forming the light scattering layer 102, a vapor deposition method, a CVD method, a spray method, a spin-on method, a dip method or the like is preferably used. Among these forming methods, as the surface protective layer 101, silicone resin, PVB
When a synthetic resin such as (polyvinyl butyral) or EVA (ethylene vinyl acetate) is used, the heat resistance of the surface protective layer is low, and therefore the substrate temperature may be set higher than the heat resistant temperature of the surface protective layer during the formation of the light scattering layer. Can not.
Therefore, as a method capable of forming the light scattering layer at a relatively low substrate temperature, a heating vapor deposition method, a DC magnetron sputtering,
RF magnetron sputtering, MOCVD, reactive ion plating, ion beam sputtering, etc., or a spray method with a low heating temperature is particularly preferably used.

Further, as suitable conditions for forming the light scattering layer in the above vapor deposition method, the substrate temperature is preferably room temperature to 250 ° C., and the gas flow rate used is preferably 0.1 sccm to 1 slm. The pressure in the reaction vessel during vapor deposition is preferably 10 ⁻⁶ Torr to 10 ⁻² Torr in the heating vapor deposition method, and preferably 1 mTorr to 1 Tor in the sputtering method.
rr is desirable.

Further, in the case of providing the uneven structure of the light scattering layer 102, in the above-mentioned forming method, the forming condition such that the surface becomes the uneven structure is appropriately selected, or after the flat layer is formed, It can be obtained by making the surface uneven by a method such as a sandblast method, a dry etching method, or a wet etching method. Other than such a forming method, the light scattering layer 102 may be formed after the surface of the surface protective layer 101 is made uneven by the above-mentioned method, and further, on the surface protective layer having an uneven structure. A light scattering layer may be formed.

When the concavo-convex structure is provided on both sides of the light scattering layer 102 with respect to the light incident direction, both of the above methods may be used.

In addition, the light scattering layer 1 is formed in the surface protective layer 101.
02 is formed by forming the surface protective layer 101, then forming the light-scattering layer 102 having a concavo-convex structure, and then forming the surface protective layer 101 again, or using a sheet-shaped surface protective layer material. There is a method of forming the light scattering layer 102 in advance and then adhering it to the substrate 107 on which the photovoltaic element is formed to form the surface protective layer 101. In addition, the light-scattering layer 1 is previously formed on the sheet-shaped surface protective layer material.
In the case of forming No. 02, the light scattering layer 102 can be adhered on the light incident side, or the surface protective layer material can be adhered on the light incident side. By appropriately selecting the bonding direction, it is possible to select whether the uneven structure is provided on the front surface side or the back surface side with respect to the light incident direction of the light scattering layer 102.

(Transparent Electrode) In the present invention, the transparent electrode 1
Reference numeral 03 denotes an electrode on the light incident side that transmits light, and can also serve as an antireflection film by optimizing the film thickness. The transparent electrode 103 is required to have high transmittance in the wavelength range in which the semiconductor layer can absorb and low resistivity. Preferably 5
The transmittance at 50 nm is 80% or more, more preferably 85% or more.

The resistivity is preferably 5 × 10 5.^-3Ω
cm or less, more preferably 1 × 10^-3Ωcm or less
Is desirable. As its material, In₂O₃, S
nO ₂, ITO (In₂O₃+ SnO₂), ZnO, C
dO, Cd₂SnO_Four, TiO₂, Ta₂O_Five, Bi₂
O₃, MoO₃, Na_x WO₃Conductive oxide such as
A mixture of these is preferably used. Also, this
These compounds are added to the elements that change the conductivity (dope
G) may be added.

As the element (dopant) for changing the conductivity, for example, when the transparent electrode 103 is ZnO, Al, In, B, Ga, Si, F, etc., and In
_In the case of ₂ O ₃ , Sn, F, Te, Ti, Sb, Pb
Etc. are SnO ₂ , F, Sb, P, As,
In, Tl, Te, W, Cl, Br, I and the like are preferably used.

As a method of forming the transparent electrode 103, a vapor deposition method, a CVD method, a spray method, a spin-on method, a dip method or the like is preferably used.

(Semiconductor Layer) The semiconductor layer 104 used in the present invention is roughly classified into a crystalline one, a polycrystalline one, an amorphous one and a combination thereof, and is in the form of a thin film or a bulk. Used. As the material of the semiconductor layer 104, a group IV element such as Si, C, or Ge is used, a group IV alloy such as SiGe, SiC, SiSn, or GaAs, InSb, Ga is used.
Those using III-V group elements such as P, GaSb, InP, InAs, ZnSe, CdTe, ZnS,
II-VI such as ZnTe, CdS, CdSe, CdTe
Those using group elements or I-such as CuInSe ₂
Those using III-VI ₂ group elements or those using them in combination are used.

Among the above-mentioned semiconductor materials, as the semiconductor material particularly preferably used in the photovoltaic device of the present invention, a-Si: H (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, or polycrystalline S
Examples include so-called group IV and group IV alloy-based polycrystalline semiconductor materials such as i: H, polycrystalline Si: F, and polycrystalline Si: H: F. This is because when a semiconductor layer is formed using a group IV and group IV alloy-based amorphous semiconductor material, the preferable thickness of the semiconductor layer is between 0.1 μm and 2.0 μm. This is because, when the thickness is 2.0 μm or less, it is considered that the effect of increasing light absorption by the semiconductor layer due to light scattering by the light scattering layer of the present invention becomes remarkable due to the light confinement effect.

Further, the semiconductor layer can perform valence electron control and forbidden band width control. Specifically, a raw material compound containing an element that becomes a valence electron control agent or a band gap control 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. It should be introduced in the space.

At least a part of the semiconductor layer 104 is p-type and n-type doped by valence electron control to form at least one set of pn junctions or at least one set of pin junctions. That is, a so-called stack cell structure in which a plurality of pn junctions or pin junctions are stacked can be used.

As a method of forming the semiconductor layer 104, a microwave plasma CVD method or an RF plasma CVD method is used.
Method, optical CVD method, thermal CVD method, various CVD method such as MOCVD method, or various evaporation methods such as EB evaporation, MBE, ion plating, ion beam method, sputtering method, spray method, printing method, etc. It is formed.
The following are group IV and I which are particularly suitable for the photovoltaic device of the present invention.
The semiconductor layer using the group V alloy-based amorphous semiconductor material will be described in more detail.

I-Type Layer (Intrinsic Semiconductor Layer) In particular, in a photovoltaic element using group IV and group IV alloy-based amorphous semiconductor materials, the i-type layer used for the pin junction generates carriers with respect to irradiation light. It is an important layer to transport.

As the i-type layer, only p-type and n-type layers can be used.

As described above, the group IV and group IV alloy amorphous semiconductor materials contain hydrogen atoms (H, D) or halogen atoms (X), and these have an important function.

The hydrogen atom (H, D) or halogen atom (X) contained in the i-type layer serves to compensate dangling bonds in the i-type layer, and the mobility and life of carriers in the i-type layer. To improve the product of P-type layer / i-type layer, n-type layer / i
It has the effect of compensating the interface states of each interface of the mold layer, and has the effect of improving the photovoltaic power, photocurrent and photoresponsiveness of the photovoltaic device. The optimum content of hydrogen atoms and / or halogen atoms contained in the i-type layer is 1 to 40 at%.

In particular, a preferable distribution form is one in which the content of hydrogen atoms and / or halogen atoms is largely distributed on the respective interface sides of the p-type layer / i-type layer and the n-type layer / i-type layer, The content of hydrogen atoms and / or halogen atoms near the interface is preferably in the range of 1.1 to 2 times the content in the bulk. Furthermore, it is preferable that the content of hydrogen atoms and / or halogen atoms is changed corresponding to the content of silicon atoms.

The layer thickness of the i-type layer depends on the structure of the photovoltaic element (for example, single cell, double cell, triple cell) and i
Depending on the band gap of the mold layer,
The optimum layer thickness is 1.0 μm.

More specifically, for example, an i-type hydrogenated amorphous silicon (a-Si: H) suitable for the photovoltaic device of the present invention has an optical bandgap (E).
g) is 1.60 eV to 1.85 eV, the content of hydrogen atoms (C _H ) is 1.0 to 25.0%, AM 1.5, 10
Photoconductivity (σp) under 0 mW / cm ² simulated sunlight irradiation
, 1.0 × 10 ^-8 S / cm or more, dark conductivity (σd)
However, 1.0 × 10 ⁻⁹ S / cm or less, the slope of the Arback tail by the constant photomethod method (CPM) is 55 meV or less, and the density of dangling bonds by electron spin resonance (ESR) is 10 ¹⁷ / cm ^3. It is as follows.

For example, i-type hydrogenated amorphous silicon germanium (a-SiGe: H) suitable for the photovoltaic device of the present invention has an optical band gap (Eg) of 1.35 eV to 1. .70 eV, hydrogen atom content (C _H ) is 1.0 to 20.0%, AM1.5,
Photoconductivity under the irradiation of 100 mW / cm ² of pseudo sunlight (σ
p) is 1.0 × 10 ⁻⁷ S / cm or more, and the dark conductivity (σ
d) is 1.0 × 10 ⁻⁵ S / cm or less, the gradient of the arback tail by the constant photomethod method (CPM) is 60 meV or less, and the density of dangling bonds by electron spin resonance (ESR) is 10 ¹⁷ / cm ³ or less.

For example, by using the group IV and group IV alloy-based amorphous semiconductor materials having the above characteristics, the transport characteristics of photocarriers are improved and the sensitivity of long wavelength light is improved. The effect of increasing the light absorption by the semiconductor layer due to the scattering of light by the light scattering layer is emphasized by the synergistic effect, and the characteristics of the photovoltaic device are further improved. This is because when the so-called localized level in the semiconductor layer is reduced due to the characteristics as described above, light is scattered by the light scattering layer and the optical path length passing through the semiconductor layer is extended, It is considered that the effect of increasing the long-wavelength light sensitivity of the photovoltaic device becomes remarkable by effectively collecting the light without recombination.

P-Type Layer or n-Type Layer The p-type layer or n-type layer is also an important layer that influences the characteristics of the photovoltaic device of the present invention.

As an amorphous material (denoted as a-) (microcrystalline material (denoted as μc-)) of the p-type layer or n-type layer, it goes without saying that it falls into the category of amorphous materials. Is, for example, a-Si: H, a-Si: HX, a-Si
C: H, a-SiC: HX, a-SiGe: H, a-S
iGeC: H, a-SiO: H, a-SiN: H, a-
SiON: HX, a-SiOCN: HX, μc-Si:
H, μc-SiC: H, μc-Si: HX, μc-Si
C: HX, μc-SiGe: H, μc-SiO: H, μ
c-SiGeC: H, μc-SiN: H, μc-SiO
N: HX, μc-SiOCN: HX, etc. and a p-type valence electron control agent (group III atom B, Al, Ga, I of the periodic table)
n, Tl) and n-type valence electron control agents (group V atoms P, As, Sb, Bi in the periodic table) are added at high concentrations, and as a polycrystalline material (indicated as poly-) Is, for example, poly-Si: H, poly-Si: H
X, poly-SiC: H, poly-SiC: HX,
poly-SiGe: H, poly-Si, poly-
A p-type valence electron control agent for SiC, poly-SiGe, etc. (Group III atom B, Al, Ga, In, T
l) and n-type valence electron control agents (group V atom P,
A material containing As, Sb, Bi) added in a high concentration can be used.

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

The amount of Group III atoms added to the p-type layer and the amount of Group V atoms added to the n-type layer were 0.
The optimum amount is 1 to 50 at%.

Hydrogen atoms (H, D) or halogen atoms contained in the p-type layer or the n-type layer serve to compensate dangling bonds in the p-type layer or the n-type layer, and the p-type layer or the n-type layer. It improves the doping efficiency of the mold layer. The hydrogen atom or halogen atom added to the p-type layer or the n-type layer is 0.1 to 40.
At% may be mentioned as the optimum amount. Especially when the p-type layer or the n-type layer is crystalline, the hydrogen atom or halogen atom is 0.1
-8 at% is mentioned as the optimum amount. Further p-type layer / i
The preferred distribution form is one in which the content of hydrogen atoms or halogen atoms is largely distributed on each interface side of the n-type layer and the n-type layer / i-type layer, and hydrogen atoms and / or halogen atoms near the interface are mentioned. Content of 1.1 to the content in the bulk
A preferable range is a double range. In this way, by increasing the content of hydrogen atoms or / halogen atoms in the vicinity of each interface of the p-type layer / i-type layer and the n-type layer / i-type layer, the defect level and mechanical strain near the interface can be reduced. It can be decreased and the photovoltaic power and photocurrent of the photovoltaic device of the present invention can be increased.

Regarding the electrical characteristics of the p-type layer or n-type layer of the photovoltaic element, the activation energy is preferably 0.2 eV or less, and most preferably 0.1 eV or less. The specific resistance is preferably 100 Ωcm or less, and 1
The optimum value is Ωcm or less. Furthermore, the layer thickness of the p-type layer and the n-type layer is preferably 1 to 50 nm, and most preferably 3 to 10 nm.

As the semiconductor layer of the photovoltaic device of the present invention,
In order to form a suitable group IV and group IV alloy-based amorphous semiconductor layer, the most preferable manufacturing method is the microwave plasma CVD method, and the next preferable manufacturing method is the RF plasma CVD method.

In the microwave plasma CVD method, a material gas such as a raw material gas and a diluent gas is introduced into a deposition chamber (vacuum chamber) which can be depressurized, and the internal pressure of the deposition chamber is kept constant while exhausting with a vacuum pump. A microwave oscillated by a microwave power source is guided by a waveguide and introduced into the deposition chamber through a dielectric window (alumina ceramics, etc.) to cause plasma of material gas to be decomposed and to be deposited in the deposition chamber. This is a method of forming a desired deposited film on the arranged substrate, and the deposited film applicable to the photovoltaic device can be formed under a wide range of deposition conditions.

When the semiconductor layer for the photovoltaic device of the present invention is deposited by the microwave plasma CVD method, 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 0.01 to 1 W / c
The preferable range of m ³ and microwave frequency is 0.5 to 10 GHz.

When depositing 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 0.01 to.
5.0 W / cm ² , deposition rate is 0.1-30 A / se
c is mentioned as a suitable condition.

As a source gas suitable for depositing the group IV and group IV alloy-based amorphous semiconductor layers suitable for the photovoltaic device of the present invention, a gasifiable compound containing silicon atoms,
Examples of a gasifiable compound containing a germanium atom, a gasifiable compound containing a carbon atom, a gasifiable compound containing a nitrogen atom, a gasifiable compound containing an oxygen atom, and a mixed gas of the compounds. You can

Specifically, gasification containing silicon atoms
SiH as the compound to be obtained_Four, Si ₂H₆, SiF_Four，
SiFH₃, SiF₂H₂, SiF₃H, Si₃H₈，
SiD_Four, SiHD₃, SiH₂D₂, SiH₃D, S
iFD₃, SiF₂D₂, SiD₃H, Si₃D
₃H₃, Etc.

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

Can be gasified specifically containing carbon atoms
CH as a compound_Four, CD_Four, C _nH_{2 n + 2}(N is
Integer) C_nH_{2 n}(N is an integer), C₂H₂, C₆H₆，
CO ₂, CO and the like.

N ₂ , NH ₃ , ND are used as the nitrogen-containing gas.
₃ , NO, NO ₂ , N ₂ O can be mentioned.

O ₂ , CO, C as oxygen-containing gas
O ₂ , NO, NO ₂ , N ₂ O, CH ₃ CH ₂ OH, CH
₃ OH and the like can be mentioned.

In order to control valence electrons, a p-type layer or n
Materials introduced into the mold layer include Group III atoms and Group V atoms of the Periodic Table.

The materials 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 specifically for introducing a boroso atom. H
Borohydrides such as ₁₁ , B ₆ H ₁₀ , B ₆ H ₁₂ , and B ₆ H ₁₄ ,
Examples thereof include boron halides such as BF ₃ and BCl ₃ . Besides this, AlCl ₃ , GaCl ₃ , In
Other examples include Cl ₃ and TlCl ₃ . Especially B ₂
H ₆ and BF ₃ are suitable.

What is effectively used as a starting material for introducing a group V atom is specifically PH for introducing a phosphorus atom.
₃ , Phosphorus hydride such as P ₂ H ₄ , PH ₄ I, PF ₃ , P
F ₅ , PCl ₃ , PCl ₅ , PBr ₃ , PBr ₅ , PI
Examples thereof include phosphorus halides such as ₃ . In addition, AsH ₃ ,
_{AsF 3, AsCl 3, AsBr 3} , AsF 5, SbH
₃ , SbF ₃ , SbF ₅ , SbCl ₃ , SbCl ₅ , B
iH _3, BiCl _3, BiBr _3, and the like can also be mentioned. Particularly, PH ₃ and PF ₃ are suitable.

Further, the gasifiable compound is replaced by H ₂ , H
It may be appropriately diluted with a gas such as e, Ne, Ar, Xe, or Kr and introduced into the deposition chamber.

In particular, when depositing a layer having a small band of light absorption or a wide band gap, such as a microcrystalline semiconductor or a-SiC: H, the source gas is diluted 2 to 100 times with hydrogen gas, and microwave power or The RF power is preferably one that introduces a relatively high power.

(Collecting Electrode) In the present invention, the collecting electrode 1
05 is formed on a part of the transparent electrode 103 if necessary when the resistivity of the transparent electrode 103 cannot be sufficiently lowered, and serves to reduce the resistivity of the electrode and the series resistance of the photovoltaic element. As the material, metal, such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, or an alloy such as stainless steel, or powder metal is used as a conductive material. Examples include paste. The shape is formed in a branch shape as shown in FIG. 4, for example, so as not to block the incident light on the semiconductor layer as much as possible.

In the entire area of the photovoltaic device,
The area occupied by the collector electrode is preferably 15% or less, more preferably 10% or less, most preferably 5% or less.

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

(Backside Electrode, Light Reflecting Layer) The backside electrode 106 used in the present invention is an electrode arranged on the backside of the semiconductor layer in the light incident direction, and its material is gold, silver, copper, aluminum or nickel. Examples include metals such as iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel.
Among these, metals with high reflectance such as aluminum, copper, silver and gold are particularly preferable. When a metal having a high reflectance is used, the back electrode can also serve as a light reflection layer that reflects light that could not be absorbed by the semiconductor layer back to the semiconductor layer.

The back electrode may have a flat shape, but it is more preferable that it has an uneven shape for scattering light. By having a concavo-convex shape that scatters light, it scatters long-wavelength light that could not be absorbed by the semiconductor layer and extends the optical path length in the semiconductor layer, improving the long-wavelength sensitivity of the photovoltaic element and increasing the short-circuit current. And the photoelectric conversion efficiency can be improved. The uneven shape that scatters light has a difference in height between peaks and valleys of Rmax of 0.2 μm to 2.0 μm.
Is desirable.

However, when the substrate also serves as the back surface electrode, there is a case where the back surface electrode need not be formed.

Further, a vapor deposition method, a sputtering method, a plating method, a printing method or the like is used for forming the back surface electrode. Further, when the back electrode is formed in a concavo-convex shape that scatters light, the formed metal or alloy film is formed by dry etching, wet etching, sand plasting, heating, or the like.
It is also possible to form an uneven shape that scatters light by vapor-depositing the above metal or alloy while heating the substrate.

(Substrate) As the material of the substrate 107 used in the present invention, either a conductive material or an insulating material can be used. Examples of the conductive material include a plate and a film made of molybdenum, tungsten, titanium, cobalt, chromium, nickel, iron, copper, tantalum, niobium, zirconium, aluminum metal or alloys thereof. Among them, stainless steel, nickel-chromium alloy and nickel, tantalum, niobium, zirconium, titanium metal and / or alloy are particularly preferable from the viewpoint of corrosion resistance. As the insulating material, polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinylidene chloride,
It is also possible to use a film or sheet of synthetic resin such as polystyrene or polyamide, or a plate-like body of an inorganic insulating material such as glass, ceramic or quartz. Alternatively, a conductive material coated with an insulating material may be used.

When a crystalline semiconductor layer is used, the crystalline semiconductor itself is used as the substrate, and the substrate 1
In some cases, 07 is not particularly required.

(Backside Protective Layer) In the present invention, the backside protective layer 108 is provided to protect the backside of the photovoltaic device.
As the material, a material having weather resistance may be appropriately selected from synthetic resins and the like.

As a forming method, usually, the film-shaped material is degassed and attached to a photovoltaic element,
It is formed by heating and melting the material or dissolving it in a solvent and applying it.

The manufacturing procedure of the photovoltaic device of the present invention is as follows.

The method for forming each layer constituting the photovoltaic device is as described above. The order of forming each layer is as follows. First, the substrate 107 is washed, the back surface electrode 106 is formed thereon, then the semiconductor layer 104, the transparent electrode 103, and the current collecting electrode 105 are formed in that order, and then the The output extraction electrode shown in the figure is formed, and finally the front surface protection layer 101 having the back surface protection layer 108 and the light scattering layer 102 formed therein is formed.

However, instead of the substrate 107, the semiconductor layer 1
When 04 is used as a substrate, it may be manufactured in an order different from the above order.

Further, when the photovoltaic devices formed on a plurality of substrates are connected in series or in parallel, or in order to reinforce the substrates, a substrate having a collector electrode formed on a support on a flat plate. After attaching, the protective layer may be formed on the front and back.

[0097]

The present invention will be described in detail below with reference to examples, but the present invention is not limited thereto.

Example 1 FIG. 2 is a sectional view showing an example of a photovoltaic device of the present invention. The photovoltaic device of FIG. 2 uses amorphous silicon (hereinafter abbreviated as a-Si) and amorphous silicon germanium (hereinafter abbreviated as a-SiGe) as semiconductor layers.

In FIG. 2, 201a, 201b, 20
1c is a surface protective layer, and the upper transparent material 20 is classified according to its function.
1a and adhesive layers 201b and 201c. Again 2
02 is a light scattering layer, 203 is a transparent electrode, and 204a, 204
Reference numerals b and 204c are semiconductor layers, 205 is a collector electrode, 206 is a back surface electrode, 207 is a substrate, 208a and 208b are adhesive layers, and 208c is a back surface protective layer. 209 is a transparent conductive layer and 210 is an insulating layer. In this embodiment, the transparent conductive layer 209 functions to prevent the back surface electrode 209 from diffusing into the semiconductor layer 204, improve the manufacturing yield of the photovoltaic device, and increase the light scattering by the back surface electrode 209. It has a function.

A photovoltaic device having the structure shown in FIG. 2 was manufactured by the following steps.

First, the surface of the substrate 207 is Rmax.
Is 0.1 μm or less, 0.7 mm thick, and 10 cm square S
A US304 stainless steel substrate is washed and the back electrode 206 is used.
As an average of 0.4 by the RF sputtering method known as
μm formed. At this time, by performing sputtering while heating the substrate to 380 ° C., Rmax is 0.6 μm.
An uneven shape that scatters m light was prepared.

Next, zinc oxide (ZnO) was formed to 0.4 μm by using the DC magnetron sputtering apparatus shown in FIG.

In FIG. 3, 301 is a vacuum container,
The heating plate 303 is supported by the supporting portion 302 having an insulating property. A heater 306 and a thermocouple 3 are provided on the heating plate 303.
04 is embedded and is controlled to a predetermined temperature by the temperature controller 305. The substrate 308 is a substrate retainer 309.
Supported by. The target 31 facing the substrate 308
0 is arranged, but the target 310 is the target table 3
The magnetic field is formed in the plasma space 320 by being installed in No. 11 and having a magnet 312 on the back surface. Cooling water is introduced from the cooling water introducing pipe 313 to the back surface of the target in order to cool the target heated during sputtering. The introduced water cools the target and then is discharged from the cooling water discharge pipe.

The target 310 is obtained by mixing zinc oxide powder with zinc and sintering it. It is also possible to use a target made of metallic zinc.

The target base 3 is attached to the target 310.
A DC voltage is applied from the sputter power supply 314 via 11. The DC current supplied from the sputtering power source is preferably set to 0.01 A or more, more preferably 0.1 A or more. According to the experiments conducted by the present inventor, the larger the current supplied to the sputter, the less the absorption of light by the zinc oxide layer to be produced, and the larger the photoelectric conversion efficiency of the photovoltaic device, especially the generated current. This also applies to the case where the zinc oxide layer is formed by using the RF type sputtering method, and the photovoltaic device manufactured by increasing the RF power is higher than the photovoltaic device when the RF power is smaller. Was also advantageous in terms of generated current.

Reference numeral 315 denotes an RF high frequency power source, which is used to apply a high frequency to the substrate side as necessary to roughen the substrate surface. The roughening of the substrate surface is performed before DC sputtering, and is intended to improve the adhesion of the film formed by DC sputtering to the substrate.

Argon gas and oxygen gas are supplied to the sputtering gas through the mass flow controller 316 or 317, respectively. Of course, it is also possible to dope fluorine with the zinc oxide layer formed by mixing the sputtering gas with another gas such as SiF ₄ or NF ₃ gas. The flow rate of the argon gas is preferably 1 sccm to 1 slm, and the flow rate of the oxygen gas is preferably 0.1 sccm to 100 sccm.
It is said that

The internal pressure can be monitored by the vacuum gauge 318 attached to the vacuum container 301. Vacuum container 3
The whole 01 is brought into a vacuum state via a main valve 319 connected to an exhaust system (not shown). The background internal pressure before starting the sputtering is preferably 10 ^−4.
The internal pressure during sputtering is 1 mTorr or more and 1To or less, more preferably 10 ^-5 Torr or less.
rr or less.

If necessary, an RF high frequency power can be applied to the substrate side by the high frequency power supply 315.

After the formation of the zinc oxide layer is started under the conditions shown above and the layer thickness of the zinc oxide layer reaches a desired value, the power supply from the sputtering power source and the sputtering gas are appropriately supplied. After stopping and appropriately cooling the substrate, the inside of the vacuum container is leaked to the atmosphere to take out the substrate on which the zinc oxide layer is formed.

Zinc oxide (ZnO) was formed by the DC magnetron sputtering apparatus configured as described above.

Thereafter, a known so-called glow discharge method (GD) in which an RF high frequency of 13.56 MHz is applied to the electrodes to decompose the raw material gas into a plasma state under reduced pressure
Method), the following semiconductor layers were formed.

First, while heating the substrate to 300.degree.
₂Diluted with monosilane (SiH _Four) And phosphine
(PH₃) Is decomposed and the n-type a-Si layer 204c is replaced with Zn.
20 nm was formed on the substrate formed to O.

Next, while heating the substrate to 250 ° C., H 2
Monosilane (SiH ₄ ) and germane (GeH ₄ ) diluted with ₂ are decomposed to give an intrinsic a-SiGe layer 204b.
Of 250 nm was formed thereon. At this time, when intrinsic a-SiGe was deposited on the glass substrate to a thickness of 1 μm under the same film forming conditions and evaluated, the optical band gap (Eg) was 1.5.
It was 0 eV.

In addition, the intrinsic a-SiGe layer 204b is formed from a-SiGe to a-Si 30 nm each in the vicinity of the n-layer and the p-layer.
A so-called buffer layer whose composition changes continuously is provided. Then, while heating the substrate to 200 ° C., H 2
Monosilane (SiH ₄ ) and boron trifluoride (BF ₃ ) diluted with ₂ are decomposed to form a p-type microcrystalline silicon layer 20.
4a was formed to 5 nm.

Next, the substrate is made 17 by resistance heating vapor deposition.
While heating to 0 ° C., ITO was vapor-deposited to 70 nm to form the transparent electrode 203.

Next, Al was vapor-deposited in a pattern as shown in FIG. 4 by using an electron beam vapor deposition method using a mask to form a collector electrode 205.

Next, a take-out electrode (not shown) was connected to the end of the back electrode and the end of the collector electrode.

Next, EVA (ethylene vinyl acetate) was hot-melted at 80 ° C. and applied on the surface of the photovoltaic device formed up to the extraction electrode, and at 1500 ° C. for 1 hour.
The surface protective layer 201c was formed by heating and curing for a time.

Next, while applying RF high frequency to the substrate side by the DC magnetron sputtering apparatus shown in FIG.
While maintaining the substrate formed up to EVA at 50 ° C, Z
nO was formed to a thickness of 1.5 μm.

Next, ZnO was etched with oxalic acid diluted to 3% with water for 180 seconds to form a concavo-convex structure with Rmax of about 1 μm on the surface to form a light scattering layer 202.

Next, a PVF film having a thickness of 40 μm is formed on the surface of the light scattering layer 202 as an upper transparent material 201a by EVA.
201b was applied and adhered. As a result, the light scattering layer 202 was formed in the surface protective layer.

Then, a nylon film having a thickness of 50 μm as an insulating layer 210 and a PVF film having a thickness of 40 μm as a back surface protective layer were applied between the back surface of the substrate 207 and EVA, and adhered to each other. The photovoltaic device of the present invention shown is completed.

Through the above steps, 20 so-called single layer type a-SiGe photovoltaic devices of 10 cm square were manufactured.

After that, the parallel resistance is 1 KΩ per cm ^2.
The above photovoltaic device was irradiated with pseudo sunlight of AM1.5, 100 mw / cm ² at 25 ° C. by a solar simulator to open voltage (Voc), short circuit current (J
sc), fill factor (FF), photoelectric conversion efficiency (η), and other photovoltaic device characteristics were measured, and the average value was obtained. Table 1 summarizes the results of photovoltaic device characteristics.

However, the characteristics of the photovoltaic device are standardized with the values of Comparative Example 1 described later.

The spectral sensitivity of the photovoltaic device was measured and is shown by the solid line in FIG. In FIG. 5, the vertical axis represents the ratio (quantum efficiency) extracted as a current with respect to the number of photons incident on the photovoltaic device.

(Comparative Example 1) The procedure of Example 1 is the same as that of Example 1 except that the light-scattering layer 202 is not formed.
e 20 photovoltaic devices were produced.

In the same manner as in Example 1, the characteristics of the photovoltaic device were measured and the average value was obtained.

Further, the spectral sensitivity of the photovoltaic device was measured in the same manner as in Example 1. The curve indicated by the chain line in FIG. 5 is for the comparative example. As is clear from FIG. 5 and Table 1, in the photovoltaic device of the present invention in which the light-scattering layer having the concavo-convex structure is formed in the surface protective layer, the photovoltaic device of Example 1 has a longer wavelength region than Comparative Example 1. The spectral sensitivity was improved, the short-circuit current (Jsc) was improved, and the photoelectric conversion efficiency (η) was improved.

[0131]

[Table 1] (Example 2) A photovoltaic device of another example of the present invention shown in FIG. 6 was manufactured by the following steps.

FIG. 6 shows a stack type photovoltaic device in which two sets of PIN junctions are laminated.

In FIG. 6, 601a, 601b and 60
1c is a surface protective layer, and the upper transparent material 60 is classified according to its function.
1a and adhesive layers 601b and 601c. Also,
602 is a light scattering layer, 603 is a transparent electrode, 604a, 60
4b, 604c, 604d, 604e, and 604f are semiconductor layers, 605 is a collector electrode, 606 is a back electrode, 607 is a substrate, and 608a and 608b are adhesive layers. Also, 60
Reference numeral 9 is a transparent conductive layer, 610 is an insulating layer, and 611 is a support which also serves as a back surface protective layer. In this embodiment, the transparent conductive layer 609 has the same function as in the first embodiment.

As shown in FIG. 6, in the photovoltaic device of this embodiment, the light scattering layer 602 is provided with unevenness on the upper and lower sides.

First, as the substrate 607, the surface has an Rmax of 0.1 μm or less, a thickness of 0.15 mm, and a width of 32 cm.
A sheet-shaped stainless steel substrate having a length of 15 m is washed, and the following treatment is performed by a so-called roll-to-roll method, in which the treatment is performed while continuously moving the substrate between a roll for delivery and a roll for winding. It was

First, Ag was formed as an average of 0.4 μm as the back electrode 606 by a known RF magnetron sputtering device using a high frequency of 13.56 MHz. At this time, by performing sputtering while heating the substrate at 380 ° C., a concavo-convex shape that scatters light of Rmax of 0.6 μm was produced.

Then, zinc oxide (ZnO) of 0.4 μm is formed as the transparent conductive layer 609 by the RF sputtering method described above.
Formed.

Next, the glow discharge method (GD method)
Then, the following semiconductor layers were formed.

First, while heating the substrate to 300 ° C., a first n-type a-Si layer 604f was formed to a thickness of 20 nm.

Next, while heating the substrate to 280 ° C., the first intrinsic a-SiGe layer 604e is formed thereon with a thickness of 250 nm.
Formed. At this time, when 1 μm of intrinsic a-SiGe was deposited on the glass substrate under the same film forming conditions and evaluated, the optical band gap (Eg) was 1.46 eV.

In addition, the intrinsic a-SiGe layer 604e is formed from a-SiGe to a-Si 30 nm each in the vicinity of the n-layer and the p-layer.
A so-called buffer layer whose composition changes continuously is provided.

Next, while heating the substrate to 260 ° C., a first p-type microcrystalline silicon layer 604d was formed to a thickness of 5 nm.

Next, while heating the substrate to 240 ° C., a second n-type a-Si layer 604c having a thickness of 20 nm was formed.

Next, while heating the substrate to 240 ° C., a second intrinsic a-Si layer 604b was formed thereon to a thickness of 220 nm.

Next, while heating the substrate to 200 ° C., a second p-type microcrystalline silicon layer 604a having a thickness of 4 nm was formed.

Next, using a DC magnetron sputtering apparatus similar to that shown in FIG.
O was vapor-deposited to a thickness of 70 nm to form a transparent electrode 603.

Next, the photovoltaic device is set to 1 by etching.
The substrate was cut into 0 cm squares and cut along the etching line.

Next, Al was vapor-deposited in the pattern as shown in FIG. 4 by electron beam vapor deposition to form a collector electrode 605.

Next, an extraction electrode (not shown) was connected to the end of the back electrode and the end of the current collecting electrode.

Next, EVA (ethylene vinyl acetate) was applied by hot-melting at 80 ° C. to a stainless steel thin plate having an irregularity of Rmax of about 3 μm on the back surface, followed by cooling and peeling from the stainless steel thin plate. To Rmax
To form an EVA film having irregularities of about 2.0 μm.

Next, diethyl zinc (DEZ) and H ₂ O were vaporized and introduced by a MOCVD device (not shown), and Z was formed at room temperature on the EVA film having the irregularities on the surface.
An average of 0.2 μm was formed for nO. In this case, the surface of the formed ZnO had irregularities of Rmax of about 0.5 μm.

Next, the support 611 having a thickness of 0.30 m
EVA is hot-melted and applied at 80 ° C. on a galvanized steel sheet having a thickness of 50 mm, which is an insulating layer 610.
Attach a nylon film of μm and EVA on it
Is applied, a photovoltaic device having the collector electrode 605 formed thereon is adhered thereon, and an EVA film having ZnO formed on the above-mentioned surface is adhered thereon, and E is further applied thereon.
VA was applied, and a PVF film having a thickness of 40 μm was attached as the upper transparent material 601a on the top to form the layer structure shown in FIG.

Finally, the whole was heated at 150 ° C. for 1 hour to cure EVA as the adhesive layer, and the photovoltaic device shown in FIG. 6 was completed.

Through the above steps, so-called Si /
100 SiGe2 stack type photovoltaic devices were produced.

[0155] In addition, the parallel resistance is more than 1kΩ per 1 cm ² photovoltaic device, at 25 ° C., by a solar simulator, by irradiating similar sunlight AM 1.5, 100 mW / cm ^2, the open-circuit voltage (Voc) , Short-circuit current (Js
c), fill factor (FF), photoelectric conversion efficiency (η)
The characteristics of the photovoltaic device such as the above were measured, and the average value was obtained.

Table 2 summarizes the results of photovoltaic device characteristics.

However, the characteristics of the photovoltaic device are standardized with the values of Comparative Example 2 described later.

(Comparative Example 2) In Example 2, the light scattering layer 602 was not provided, and otherwise the procedure was the same as that of Example 2, and a 10 cm square so-called two-layer stack type photovoltaic layer of Si / SiGe was used. 100 devices were produced.

In the same manner as in Example 2, the characteristics of the photovoltaic device were measured and the average value was obtained.

As is clear from Table 2, the short-circuit current (Jsc) of the SiGe cell is particularly improved by the photovoltaic device of the present invention in which the light scattering layer having the uneven structure is formed in the surface protective layer.
, Thereby improving the overall short-circuit current (Jsc) and fill factor (FF), and improving the photoelectric conversion efficiency (η).
Has improved.

[0161]

[Table 2] (Example 3) In the following steps, a photovoltaic device of another example of the present invention shown in Fig. 7 was manufactured.

FIG. 7 shows an example of a photovoltaic device of the present invention using a semiconductor layer of II-VI group element.

In FIG. 7, 701a, 701b and 70
1c is a surface protective layer, and the upper transparent material 70 is classified according to its function.
1a and adhesive layers 701b and 701c. Again 7
02 is a light scattering layer, 703 is a transparent electrode, and 704a is n-type C.
dS semiconductor layer, 704b is a p-type CdTe semiconductor layer, 70
Reference numerals 6a and 706b denote back surface electrodes, and 707 denotes a substrate which also serves as a back surface protective layer.

First, the surface of the substrate 701 is Rmax.
0.1 μm or less, thickness 0.18 mm, width 32 c
A sheet-like polyethylene terephthalate (PET) film having a length of 10 m and a length of 10 m was used as a substrate for cleaning, and Example 2 was used.
The following treatment was performed by the so-called roll-to-roll method similar to the above.

First, by using the DC magnetron sputtering apparatus shown in FIG.
μm formed. Next, 20 nm of Au was formed as the back surface electrode 706a by the same DC magnetron sputtering apparatus.

Then, the semiconductor layer of the photovoltaic device shown in FIG. 7 was manufactured by the following steps.

First, while heating the substrate at 160 ° C., the p-type CdTe layer 704b was formed to a thickness of 1.5 μm by the vacuum evaporation method.
Formed.

Next, while heating the substrate at 150 ° C., the n-type CdS layer 704a was formed to a thickness of 0.1 μm by the vacuum evaporation method.
Formed.

Next, with a DC magnetron sputtering apparatus similar to that shown in FIG.
O was vapor-deposited to a thickness of 200 nm to form a transparent electrode 703.

After that, heat treatment was performed at 120 ° C. for 1 hour in an N ₂ atmosphere.

Next, the photovoltaic device is set to 1 by etching.
The substrate was cut into 0 cm squares and cut along the etching line.

Next, an extraction electrode (not shown) was connected to the end of the transparent electrode and the end of the collector electrode.

Next, polyvinyl butyral (PVB) was applied as the adhesive layer 701c. Then, TiO ₂ was formed to ₂ μm on PVB at room temperature by the reactive ion plating method.

After that, dry etching is performed with plasma of a mixed gas of CF ₄ and O ₂ to obtain TiO 2.
Roughness of 0.6 μm was formed on the surface of No. ₂ by Rmax to form a light scattering layer 702.

Next, a silicone resin was applied as an adhesive layer 701b on TiO ₂ , and a PVF film having a thickness of 30 μm was adhered as an upper transparent material 701a.

Through the above steps, 200 so-called CdS / CdTe photovoltaic devices of 10 cm square shown in FIG. 7 were produced.

The parallel resistance is 1 kΩ per cm ^2.
The above photovoltaic device was irradiated with artificial sunlight of AM 1.5 and 100 mW / cm ² at 25 ° C. by a solar simulator to open voltage (Voc) and short circuit current (J
sc), fill factor (FF), photoelectric conversion efficiency (η), and other photovoltaic device characteristics were measured, and the average value was obtained. Table 3 summarizes the results of photovoltaic device characteristics.

However, the characteristics of the photovoltaic device are standardized with the values of Comparative Example 3 described later.

Comparative Example 3 The light scattering layer 7 in Example 3
In the same procedure as in Example 3 except that 02 was not provided, 200 10 cm square so-called CdS / CdTe photovoltaic devices were manufactured.

In the same manner as in Example 3, the characteristics of the photovoltaic device were measured and the average value was obtained.

As is apparent from Table 3, the photovoltaic device of the present invention in which the light-scattering layer having the uneven structure is formed in the surface protective layer improves the short-circuit current (Jsc) and improves the photoelectric conversion efficiency (η). Has improved.

[0182]

[Table 3] (Example 4) A photovoltaic device according to still another example of the present invention shown in FIG. 8 was manufactured by the following steps.

FIG. 8 shows an example of the photovoltaic device of the present invention using polycrystalline silicon as the semiconductor layer.

In FIG. 8, 801a, 801b, 80
Reference numerals 1c, 801d, 801e, and 801f are surface protection layers, and upper transparent materials 801a, 801c, and 80 are classified according to their functions.
1e and filling layers 801b, 801d, and 801f. Further, 802a and 802b are light scattering layers, 803 is an antireflection layer or a transparent electrode also serving as an antireflection layer, 804
a and 804b are polycrystalline silicon semiconductor substrates,
4a is a portion converted to a conductivity type opposite to the semiconductor substrate. Further, 806 is a back surface electrode, 808 is a back surface filling layer, 8
Reference numeral 11 is a support which also serves as a back surface protection layer, and 812 is a back surface passivation layer of the semiconductor substrate.

First, a p-type polycrystalline silicon substrate having a thickness of 150 μm formed by the casting method is prepared,
After cleaning the surface of the substrate, the surface 804a was converted to n ⁺ type by an ion implantation method to form a pn junction.

Next, a passivation layer of SiO ₂ (not shown) having a thickness of 5 nm was formed on the surface of the polycrystalline silicon substrate on which the pn junction was formed.

Next, a thickness of 2 is formed on the back surface of the polycrystalline silicon substrate.
A 00 nm Si ₃ N ₄ passivation layer was formed.

Next, a collector electrode 805 and a back electrode 806 of Ti and Ag were formed on the front surface and the back surface of the polycrystalline silicon substrate on which the passivation layer was formed.

Next, the transparent electrode 803 which also functions as an antireflection layer.
As a result, Ta ₂ O ₅ having a thickness of 0.2 μm was formed at a substrate temperature of 200 ° C. by using a DC magnetron sputtering apparatus similar to that shown in FIG.

On the other hand, Ta ₂ O ₅ having a thickness of 3.0 μm was formed on a polyimide film having a thickness of 30 μm at a substrate temperature of 200 ° C. by a DC magnetron sputtering apparatus similar to that shown in FIG.

Then, Ta ₂ O ₅ was etched with acetic acid diluted to 5% with water for 120 seconds to obtain Rmax of 1.5 μm.
An uneven structure of a certain degree was formed on the surface to form a light scattering layer.

Next, a support 811 of an Al plate having a thickness of 1 mm
A photovoltaic device having transparent electrodes formed thereon, two polyimide films having Ta ₂ O ₅ having irregularities on the surface thereof formed thereon, and a PVF film serving as an upper transparent material 801a formed on the top of the photovoltaic device. As a packed bed between the EV
A was applied and attached. At this time, extraction electrodes (not shown) were formed at the ends of the collector electrode 805 and the back surface electrode 806.

Then, the whole was heated at 150 ° C. for 1 hour to cure the EVA, and the photovoltaic device of the present invention shown in FIG. 8 was completed.

Through the above steps, fifty 10 cm square polycrystalline silicon photovoltaic devices of FIG. 8 were manufactured.

The parallel resistance is 1 kΩ per cm ^2.
The above photovoltaic device was irradiated with pseudo sunlight of AM1.5, 100 mw / cm ² at 25 ° C. by a solar simulator to open voltage (Voc), short circuit current (J
sc), fill factor (FF), photoelectric conversion efficiency (η), and other photovoltaic device characteristics were measured, and the average value was obtained. Table 4 summarizes the results of photovoltaic device characteristics.

However, the characteristics of the photovoltaic device are standardized with the values of Comparative Example 5 described later.

(Comparative Example 4) In Example 4, the light scattering layer 802b was not provided and only one light scattering layer was provided.
Fifty angled polycrystalline silicon photovoltaic devices were fabricated.

In the same manner as in Example 4, the characteristics of the photovoltaic device were measured and the average value was obtained.

(Comparative Example 5) In Example 4, the light scattering layers 802a and 802b were not provided, and the procedure was the same as that of Example 4 except that 50 pieces of 10 cm square polycrystalline silicon photovoltaic devices were used. It was made.

In the same manner as in Example 4, the characteristics of the photovoltaic device were measured and the average value was obtained.

As is clear from Table 4, the photovoltaic device of the present invention in which the light-scattering layer having the uneven structure is formed in the surface protective layer improves the short-circuit current (Jsc) and improves the photoelectric conversion efficiency (η). Has improved. Moreover, the short-circuit current (Jsc) was further improved and the photoelectric conversion efficiency (η) was improved by using two light scattering layers.

[0202]

[Table 4] (Example 5) A photovoltaic device according to still another example of the present invention was manufactured by the following steps.

The present embodiment is an example of the photovoltaic device of the present invention in which unevenness is provided on both front and back surfaces of the light scattering layer and single crystal GaAs is used as the semiconductor layer in the photovoltaic device having the configuration of FIG. .

First, an n-type GaAs wafer having a thickness of 200 μm was prepared, and an n-type GaAs layer doped with sulfur (S) was formed by 5.0 μm by the MOCVD method.
Next, p doped with Zn by MOCVD method
A p-type GaAs layer was formed in the order of 5.0 μm, a p-type AlGaAs layer doped with Zn was 0.15 μm, and a p-type GaAs layer doped with Zn was 0.5 μm in this order to form a pn junction.

Next, an antireflection layer of Si ₃ N ₄ (not shown) having a thickness of 75 nm was formed on the surface of the GaAs wafer on which the pn junction was formed.

Next, a GaAs wafer having a thickness of 20 is formed on the back surface thereof.
A 0 nm Si ₃ N ₄ passivation layer was formed.

Next, Ga with a passivation layer was formed.
A Ti and Ag collector electrode 805 and a back electrode 806 were formed on the front and back surfaces of the As wafer.

On the other hand, PET was hot-melted and applied on a stainless thin plate having an irregularity of about 5 μm at Rmax on the surface, then cooled and peeled off from the thin stainless plate, and an irregularity of about 2.0 μm at Rmax was formed on the surface. Having a PET film having.

[0209] Then, the above PET film was subjected to reactive ion plating at a substrate temperature of 120 ° C to obtain Mg.
F ₂ was formed to a thickness of ₂ μm. After that, dry etching was performed with plasma of a mixed gas of NF ₃ and O ₂ to form irregularities of 0.6 μm in Rmax on the surface of MgF ₂ . As a result, MgF having irregularities on both front and back surfaces
_Two light-scattering layers were formed.

Next, a support 811 of an Al plate having a thickness of 1 mm
A photovoltaic device having a collector electrode formed thereon, two PET films having MgF ₂ having irregularities on the surface formed thereon, and a PV film having an upper transparent material 801a at the top.
EVA was applied and stuck with the F film as a filling layer between them. At this time, extraction electrodes (not shown) were formed at the ends of the collector electrode 805 and the back surface electrode 806.

Then, the whole was heated at 150 ° C. for 1 hour to cure the EVA, and the photovoltaic device of the present invention shown in FIG. 8 was completed.

Through the above steps, 20 GaAs photovoltaic devices each having a diameter of 3 inches were manufactured.

The parallel resistance is 1 kΩ per cm ^2.
The above photovoltaic device was irradiated with artificial sunlight of AM 1.5 and 100 mW / cm ² at 25 ° C. by a solar simulator to open voltage (Voc) and short circuit current (J
sc), fill factor (FF), photoelectric conversion efficiency (η), and other photovoltaic device characteristics were measured, and the average value was obtained. Photovoltaic device characteristics such as photoelectric conversion efficiency (η) were measured, and an average value was obtained.

The results of photovoltaic device characteristics are summarized in Table 5.

However, the characteristics of the photovoltaic device are standardized with the values of Comparative Example 7 described later.

(Comparative Example 6) In Example 5, the light scattering layer 802b was not provided, and only one light scattering layer was used. Otherwise, the procedure was exactly the same as that of Example 5, and the GaAs light having a diameter of 3 inches was used. 20 electromotive force devices were produced.

In the same manner as in Example 5, the characteristics of the photovoltaic device were measured and the average value was obtained.

(Comparative Example 7) In Example 5, 20 GaAs photovoltaic devices each having a diameter of 3 inches were prepared in the same procedure as in Example 5 except that the light scattering layers 802a and 802b were not provided. did.

In the same manner as in Example 5, the characteristics of the photovoltaic device were measured and the average value was obtained.

As is clear from Table 5, the photovoltaic device of the present invention in which the light-scattering layer having an uneven structure is formed in the surface protective layer improves the short-circuit current (Jsc) and improves the photoelectric conversion efficiency (η). Has improved. Moreover, the short-circuit current (Jsc) was further improved and the photoelectric conversion efficiency (η) was improved by using two light scattering layers.

[0221]

[Table 5]

[0222]

As described above, according to the inventions of claims 1 to 4, since the light-scattering layer having the concavo-convex structure is provided in the surface-protecting layer on the light-incident side, the photo-generating layer is formed. Light incident on the power device is incident on the semiconductor layer after being scattered in the surface protective layer, the optical path length in the semiconductor layer is extended, the absorption of light by the semiconductor layer is increased, and the short-circuit current is increased. The photoelectric conversion efficiency can be improved.

According to the fifth aspect of the present invention, if a plurality of light scattering layers having the concavo-convex structure are formed in the surface protective layer, the scattering of incident light is further increased, and the light generated by the semiconductor layer is further increased. Is increased and the short-circuit current is increased, so that the photoelectric conversion efficiency of the photovoltaic device can be further improved.

According to the invention of claim 6, the difference between the refractive index of the substance forming the light scattering layer and the refractive index of the substance forming the surface protective layer is set to 0.1 or more. Since the scattering of incident light is increased, the absorption of light by the semiconductor layer is increased, the short-circuit current is increased, and the photoelectric conversion efficiency can be further improved.

Furthermore, according to the invention of claim 7, the light incident on the photovoltaic device is scattered on both the incident side and the reflecting side, and the light absorption by the semiconductor layer is further increased. It is possible to realize an increase and an improvement in photoelectric conversion efficiency.

In general, according to the present invention, the optical path length in the semiconductor layer is extended and the absorption of light by the semiconductor layer is increased, so that the thickness of the semiconductor layer can be reduced. Therefore, for example, when an amorphous semiconductor is used as the semiconductor layer, generation of photo-induced defects in the semiconductor layer is suppressed, and deterioration of photoelectric conversion efficiency of the photovoltaic device due to light irradiation (so-called photo-deterioration) is suppressed. To be done.

Furthermore, for example, when a crystalline semiconductor is used as the semiconductor layer, the thickness of the semiconductor substrate can be reduced to reduce the weight of the photovoltaic device, and the reduction of semiconductor materials can reduce the manufacturing cost. I can contribute.

[Brief description of drawings]

FIG. 1 is a conceptual schematic diagram of a photovoltaic device according to the present invention.

FIG. 2 is a sectional view showing an example of a photovoltaic device of the present invention.

FIG. 3 is a cross-sectional view of an example of a manufacturing apparatus for forming a light scattering layer of the photovoltaic device of the present invention.

FIG. 4 is a schematic view of an example of the photovoltaic device of the present invention.

FIG. 5 is a graph showing the spectral sensitivity of an example of the photovoltaic device of the present invention.

FIG. 6 is a cross-sectional view showing another example of the photovoltaic device of the present invention.

FIG. 7 is a cross-sectional view showing still another example of the photovoltaic device of the present invention.

FIG. 8 is a cross-sectional view showing still another example of the photovoltaic device of the present invention.

[Explanation of symbols]

101, 201, 601, 701, 801 Surface protective layer 102, 202, 602, 702, 802 Light scattering layer 103, 203, 603, 703, 803 Transparent electrode 104, 204, 604, 704, 804 Semiconductor layer 105, 205, 605, 805 Current collecting electrode 106, 206, 606, 706, 806 Back surface electrode (light reflection layer) 107, 207, 607, 707 Substrate 108, 208, 608, 808 Back surface protection layer 209, 609 Transparent conductive layer 210, 610 Insulation Layer 611 Support 301 Vacuum container 302 Support part 303 Heating plate 304 Thermocouple 305 Temperature controller 306 Heater 307 Heat transfer plate 308 Substrate 309 Substrate retainer 310 Target 311 Target stand 312 Magnet 313 Cooling water introduction pipe 314 Sputtering power source 31 The light incident surface 402 out electrode of the high-frequency power source 316, 317 the mass flow controllers 318 gauge 319 main valve 320 plasma space 401 photovoltaic device

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Koichi Matsuda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc. (72) Inventor Yuzo Koda 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon (72) Inventor Naoto Okada 3-30-2 Shimomaruko, Ota-ku, Tokyo Canon Inc.

Claims (7)

[Claims] 1. A photovoltaic device comprising a surface protective layer laminated on a light incident side of a semiconductor layer, wherein the surface protective layer has a refractive index different from that of the surface protective layer and an uneven structure. A photovoltaic device having at least one light-scattering layer. 2. The photovoltaic device according to claim 1, wherein the light scattering layer has a concavo-convex structure on the surface side with respect to the light incident direction. 3. The photovoltaic device according to claim 1, wherein the light scattering layer has a concavo-convex structure on the back surface side with respect to the light incident direction. 4. The photovoltaic device according to claim 1, wherein the light scattering layer has a concavo-convex structure on both the front surface and the back surface with respect to the light incident direction. 5. The photovoltaic device according to claim 1, wherein the uneven structure has a surface roughness Rmax value of 0.05 μm to 100 μm. apparatus. 6. The difference between the refractive index of the material forming the surface protective layer and the refractive index of the material forming the light scattering layer is 0.
It is 1 or more, The photovoltaic device of any one of Claim 1 to 5 characterized by the above-mentioned. 7. The light reflection layer for scattering light is formed on the side opposite to the light incident light side with respect to the semiconductor layer, according to any one of claims 1 to 6. Photovoltaic device.