JP3072831B2 - Photovoltaic element - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a photovoltaic device having a back reflection layer.

[0002]

2. Description of the Related Art Conventionally, it has been known that a metal reflection layer is provided on a side opposite to a light incident side of a photoelectric conversion layer in order to increase the conversion efficiency of a photovoltaic element, and the incident light is effectively used. I have. In addition, by providing a transparent conductive layer between the metal reflection layer and the photoelectric conversion layer, it is possible to prevent the components of the metal reflection layer from diffusing into the photoelectric conversion layer, and at the same time, when a short circuit occurs in the photoelectric conversion layer, It has been known that the flow of water can be prevented and the adhesion of the photoelectric conversion layer is further improved. This is described, for example, in JP-B-59-43101, JP-B-60-43101.
-41878 and Japanese Patent Publication No. 60-84888. In addition, TiO is provided between the metal layer and the photoelectric conversion layer.
_{2 through} the transparent conductive layer. Hamaka
wa, et. al, Appl. Phys. Lett. ,
43 (1983) p644.

Further, by forming a so-called texture structure in which the surface of the transparent conductive layer is made to have fine irregularities,
It is known that light is scattered at the interface between the transparent conductive layer and the photoelectric conversion layer to achieve more effective light absorption. This is for example T. Toedje, et. al, Proc. 16th
IEEE Photovoltaic Special
ist Conf. (1982) p1425.

[0004]

However, when a photovoltaic element is actually manufactured by employing the back electrode having such a structure, there are some problems in view of workability and durability. Have been.

[0005] On the one hand, a typical concavo-convex shape called a conventional so-called texture structure is described in US Pat. Tiedje,
et. al, Proc. 16th IEEE Photo
ovoltaic Specialist Conf.
(1982) It has been considered that a material having pyramid-shaped irregularities as shown in p1423 has an excellent light confinement effect. However, when a transparent conductive layer is formed on a substrate having such a surface shape, the surface of the transparent conductive layer also has pyramid-shaped irregularities. The leakage current of the photovoltaic element may increase through a defective portion of the layer or the like, and the production yield of the photovoltaic element may decrease. In addition, the semiconductor layer formed on the surface having pyramid-shaped irregularities has a smaller effective film thickness than the semiconductor layer formed on the mirror surface, so that the originally designed thin doping layer is further thinned. That is, the open-circuit voltage (Voc) and the fill factor (FF) of the photovoltaic element may be lower than those of the photovoltaic element formed on the mirror-finished substrate surface.

Further, for example, when Ag or Cu is used as the back metal reflective layer, when the humidity is high and a positive bias voltage is applied to the back metal reflective layer, Ag or Cu migrates to cause the light incident side. And the photovoltaic element was shunted (short-circuited). This phenomenon was remarkable when the back metal reflection layer had an uneven shape (texture structure) having a size about the wavelength of light.

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

On the other hand, the substrate for the photovoltaic element was originally
From the viewpoint of characteristics and yield, a material having a surface roughness as small as possible and close to a mirror surface has been favorably used. However, when the back surface reflection layer or the substrate and the back surface reflection layer are formed in a mirror surface having a diffuse reflectance of 1% or less, instead of a concave-convex shape, the surface of the transparent conductive layer becomes flat, and light scattering on the back surface is small. Depending on the problem of insufficient light absorption of the semiconductor layer and the combination of the materials of the substrate and the back electrode, the adhesion between the substrate and the back reflection layer or the back reflection layer and the transparent conductive layer or between the transparent conductive layer and the semiconductor is insufficient. In addition, there has been a problem that in the processing step of the photovoltaic element, peeling is likely to occur at any interface of each layer. Polishing the substrate to a mirror surface also has the problem of increasing the production cost of the substrate and increasing the production cost of the photovoltaic element.

[0009] The above problems are caused by using low-cost substrates such as resin films and stainless steel, and increasing the production speed by increasing the formation speed of the semiconductor layer. This is particularly noticeable when the process is employed, and has been a factor in lowering the production yield of the photovoltaic element.

(Object of the Invention) An object of the present invention is to solve the problems of workability, yield and durability as described above by making the substrate including the transparent conductive layer a new structure, and It is an object of the present invention to provide a thin-film photovoltaic element which increases the light absorption of a semiconductor layer, can be produced at a high yield, has high reliability, and has high photoelectric conversion efficiency, at low cost suitable for practical use.

[0011]

Means for Solving the Problems The present inventors have overcome the above-mentioned problems of processability and reliability, and have increased the light absorption of the semiconductor layer and at the same time have a photovoltaic device excellent in processability and reliability. In order to obtain a power device, a new structure and a new method of forming a transparent conductive layer interposed between the rear reflective layer and the semiconductor layer have been studied. Achieved by power elements.

The photovoltaic device of the present invention that achieves the above object is formed by sequentially laminating at least a substrate, a back reflection layer, a transparent conductive layer, and a photoelectric conversion layer containing silicon and germanium. Or, the surface of the back reflection layer is not a mirror surface, nor has pyramid-shaped irregularities formed thereon, and has an appropriate surface roughness of 3% or more and 50% or less in diffuse reflectance of light having a wavelength of 800 nm,
Further, the transmittance of the transparent conductive layer for light having a wavelength of 650 nm or more is 80% or more.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the structure of a photovoltaic device according to the present invention and a method for manufacturing the same will be described in more detail with reference to the drawings.

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

The substrate 101 and the back metal reflection layer 102
An adhesion layer for improving the adhesion of the back metal reflection layer to the substrate may be inserted between them.

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

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

(Substrate) As a substrate suitable for the present invention, the surface shape of the photovoltaic element is required to suppress the leak current, maintain a high production yield, and enhance the adhesion to the backside reflection layer. Is a preferable range. That is, the surface of the substrate is not a mirror surface, nor has pyramid-shaped irregularities formed thereon, but has an appropriate surface roughness such that the diffuse reflectance of light having a wavelength of 800 nm is 3% or more and 50% or less. Is preferably used. With the substrate having such a surface shape, the leakage current of the photovoltaic element is suppressed, the adhesion to the back reflection layer is increased, the production yield of the photovoltaic element is improved, and the weather resistance and durability are improved. Performance can be improved. However, when the thickness of the back metal reflective layer is large and a desired diffuse reflectance can be formed, a substrate having a diffuse reflectance outside the above range can be used.

The material of the substrate may be a single crystalline or non-single crystalline material, and furthermore, they may be conductive or electrically insulating. . Further, they may be light-transmitting or non-light-transmitting, but preferably have a small amount of deformation and distortion and a desired strength. Specifically, Fe, Ni, Cr, Al, Mo, Au,
Metals such as Nb, Ta, V, Ti, Pt, Pb or alloys thereof, for example, thin plates such as brass and stainless steel and composites thereof, and polyester, polyethylene, polycarbonate, cellulose acetate, polypropylene, polyvinyl chloride, polyvinyl chloride Films or sheets of heat-resistant synthetic resins such as vinylidene, polystyrene, polyamide, polyimide, epoxy or composites of these with glass fibers, carbon fibers, boron fibers, metal fibers, etc., and thin plates of these metals, resin sheets, etc. Metal thin films of different materials and / or SiO ₂ , Si on the surface
_{3 N 4, Al 2 O 3} , sputtering an insulating film such as AlN,
Examples thereof include those subjected to a surface coating treatment by a vapor deposition method, a plating method, and the like, glass, ceramics, and the like. Among the above materials, stainless steel is particularly excellent in workability and durability.

When the substrate is electrically conductive such as metal, it may be used as an electrode for direct current extraction. When the substrate is electrically insulating such as synthetic resin, the surface on which the deposited film is formed may be formed. Al, Ag, Pt, Au, Ni, Ti, M
o, W, Fe, V, Cr, Cu, stainless steel, brass, Nichrome, SnO ₂ , In ₂ O ₃ , ZnO, ITO, and other so-called simple metals or alloys, and transparent conductive oxide (TCO) are plated and deposited. It is preferable that a surface treatment is performed in advance by a method such as sputtering to form an electrode for extracting current.

Of course, even if the substrate is made of an electrically conductive material such as a metal, the reflectance of long-wavelength light on the substrate surface can be improved or the mutual diffusion of constituent elements between the substrate material and the deposited film can be improved. A different kind of metal layer or the like may be provided on the side of the substrate on which the deposited film is formed, for the purpose of preventing the like.

The shape of the substrate can be plate-like, long belt-like, cylindrical or the like, and its thickness is appropriately determined so as to form a photovoltaic element as desired. When the element is required to have flexibility, or when light is incident from the side of the substrate, the element can be made as thin as possible within a range where the function as the substrate is sufficiently exhibited. However, the thickness is usually 10 μm or more from the viewpoint of manufacturing and handling of the substrate, mechanical strength and the like.

(Backside Reflection Layer) The backside metal reflection layers 102 and 202 used in the present invention are disposed on the backside of the semiconductor layer in the light incident direction, and reflect the light that could not be absorbed by the semiconductor layer back to the semiconductor layer. Has the role of a light reflecting layer. In addition, it also serves as the back electrode of the photovoltaic element.

The surface roughness of the back metal reflective layer is one of the features of the present invention. The surface roughness is not a mirror surface, nor does it have pyramid-shaped irregularities. Preferably, those having an appropriate surface roughness of 3% or more and 50% or less, more preferably 10% or more and 45% or less are suitably used. By such a back metal reflective layer, the adhesion between the back metal reflective layer and the transparent conductive layer is improved, and the flexibility and controllability of the manufacturing process of the photovoltaic element are improved. Spreading is suppressed,
The leakage current of the photovoltaic element was reduced, the production yield of the photovoltaic element was improved, and the weather resistance and durability were improved. In addition, the orientation of the polycrystalline transparent conductive layer is improved, the average particle size of the polycrystalline transparent conductive layer is increased, the variation in particle size is reduced, and conical or pyramidal holes are formed on the surface of the transparent conductive layer. Is easy to form. As a result, light scattering on the surfaces of the back metal reflection layer and the transparent conductive layer was promoted, and the short-circuit current (Jsc) could be increased.

In a photovoltaic element in which a plurality of pin junctions are stacked thereon, the short wavelength light is normally absorbed by the pin junction on the light incident side and the long wavelength light is absorbed by the pin junction on the substrate side. Further, the light that has not been absorbed is reflected by the surface reflection layer and returned to the semiconductor layer. Here, with respect to light having a long wavelength of 800 nm, it has been found that when the diffuse reflectance of the back reflection layer is 3% to 50%, the characteristics of the element are improved.

When the thickness of the back metal reflection layer is reduced to, for example, 0.1 μm or less, the surface of the back metal reflection layer has a shape inheriting the surface properties of the substrate. When the thickness of the back metal reflection layer is increased to, for example, 1 μm or more, the surface becomes relatively flat.

As the material of the back metal reflection layer, gold, silver,
Examples thereof include metals such as copper, aluminum, magnesium, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium, and alloys such as stainless steel. Among them, metals having high reflectivity, such as aluminum, magnesium, copper, silver, and gold, or alloys containing these high reflectivity metals as main components and other metals or silicon are particularly preferable. By using a metal with a high reflectance, light that could not be absorbed by the semiconductor layer is reflected again by the semiconductor layer with a high reflectance,
The optical path length in the semiconductor layer increases, the light absorption of the semiconductor layer increases, and the short-circuit current (Jsc) of the photovoltaic element increases.

The back metal reflective layer may be formed by laminating two or more kinds of materials in two or more layers.

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

The method of forming the surface of the back metal reflective layer so as to have a diffuse reflectance in the above range differs depending on the material and the film forming method of the back metal reflective layer.
It can be obtained by appropriately increasing the substrate temperature during film formation. Alternatively, it may be formed by polishing or etching after the film formation. It can also be obtained by forming a back metal reflective layer on a substrate having a suitable diffuse reflectance.

(Transparent Conductive Layer) The transparent conductive layer 103 is disposed between the back metal reflective layer 102 and the semiconductor layer 104 for the following purposes. First, the irregular reflection on the back surface of the photovoltaic device is improved, light is confined in the photovoltaic device by multiple interference by a thin film, the optical path length in the semiconductor layer is extended, and the short-circuit current (Jsc) of the photovoltaic device is increased. To increase. Next, it is necessary to prevent the metal of the back metal reflection layer also serving as the back electrode from diffusing or migrating into the semiconductor layer, thereby preventing the photovoltaic element from shunting. Further, by giving the transparent conductive layer a slight resistance value, the back metal reflection layer 102 provided with the semiconductor layer interposed therebetween is provided.
It is to prevent a short circuit generated due to a defect such as a pinhole in the semiconductor layer between the semiconductor device and the transparent electrode 107.

The surface shape of the transparent conductive layer 103 is one of the features of the present invention, and the holes are formed in a dispersed manner. The shape of the hole is preferably conical or pyramidal. Due to the transparent conductive layer having such a surface shape, light is effectively confined in the photovoltaic element, and a high short-circuit current (Jsc) is maintained even with a smaller surface area than a conventional pyramid-shaped uneven surface. In addition, the open voltage (Voc) and the fill factor (FF) could be improved. In addition, the adhesion between the transparent conductive layer and the semiconductor layer was improved, the shunt of the photovoltaic element was prevented, the production yield was improved, and the weather resistance and durability were improved.

Further, the average diameter of the conical or pyramid-shaped hole is d, the average depth is h, the average density is ρ, and the coefficients C ₁ and C ₂ are C ₁ = h / d C ₂ = ρ × d ² Where d is preferably from 0.05 μm to 2
μm, more preferably 0.1 μm to 1.5 μm, and most preferably 0.2 μm to 1 μm.

C ₁ is preferably from 0.2 to 0.5.
9, more preferably 0.3 to 0.6.

C ₂ is preferably 0.02 to 1.0, and more preferably 0.1 to 0.8.

The average diameter d of a conical or pyramidal hole,
By optimizing the coefficients C ₁ and C ₂ in such a range, an effect that further emphasizes the effect of the present invention was obtained.

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

The material of the transparent conductive layer 103 is In ₂
O ₃ , SnO ₂ , ITO (In ₂ O ₃ + SnO ₂ ), Zn
O, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta ₂ O ₅ , Bi ₂
A conductive oxide such as O ₃ , MoO ₃ , and Na _x WO ₃ or a mixture thereof is suitably used. Further, an element (dopant) that changes the conductivity may be added to these compounds. Among the above materials, ZnO has an appropriate resistance value, and because it has a C-axis orientation, it is easy to form a conical or pyramid-shaped hole on the surface, and the semiconductor layer It is particularly preferably used due to its durability against plasma and the like during formation.

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

As the method for forming the transparent conductive layer 103, various deposition methods such as EB deposition and sputter deposition, and various C
A VD method, a spray method, a spin-on method, a dipping method and the like are preferably used.

(Method of Forming Holes on Surface of Transparent Conductive Layer) As a method of forming conical or pyramid-shaped holes on the surface of the transparent conductive layer 103 by dispersing, when the transparent conductive layer is polycrystalline, There is a method of forming the crystal by controlling the crystal growth of the crystal, or a method of forming the transparent conductive layer and then performing etching in a gas phase or a liquid phase.

As a method for controlling the crystal growth of polycrystal, the surface condition of the back metal reflective layer for forming the transparent conductive layer and the conditions for forming the transparent conductive layer can be mentioned.

The surface state of the back reflection layer greatly affects the initial state of crystal growth. If the irregularities are too large, the nucleation density of the crystal will be too large, and the grain size at the initial stage of crystal growth will be too small. In addition, when the surface of the back reflection layer is a mirror surface, a problem of peeling occurs with the transparent conductive layer. Therefore, a moderate crystal nucleation density can be obtained by a surface state in which the diffuse reflectance at a wavelength of 800 nm of the surface of the backside reflection layer at a wavelength of 800 nm is 3% or more and 50% or less. It is believed that this promotes crystal growth with proper orientation to form holes.

The suitable conditions for forming the transparent conductive layer differ depending on the type of the transparent conductive layer and the film forming method. The type and flow rate of the gas, the internal pressure, the input power, the film forming speed, the substrate temperature and the like are different. It has a significant effect. For example, when depositing ZnO by DC magnetron sputtering, the type of gas is A
Examples thereof include r, Ne, Kr, Xe, Hg, and O _{2. The} flow rate varies depending on the size of the apparatus and the pumping speed. For example, when the volume of the film forming space is 20 liters, the flow rate is preferably 10 sccm to 100 sccm. The internal pressure during film formation is 1
It is preferable that the pressure be from ^10-4 Torr to 0.1 Torr. The preferred range of input power varies depending on the material to be deposited.
When the size of the target is 15 cm in diameter, 100 W to 1000 W is desirable. The preferred range of the substrate temperature varies depending on the film formation rate.
When forming a film at μm / h, preferably from 70 ° C. to 450 ° C.
° C, more preferably 100 ° C to 350 ° C, optimally 1 ° C
Desirably, the temperature is from 50 ° C to 250 ° C.

As described above, by combining the preferable surface condition of the back metal reflective layer and the preferable film forming conditions of the transparent conductive layer, a polycrystal having a small grain size is formed near the interface with the back metal reflective layer. On top of this, polycrystals having a larger grain size were formed in a columnar orientation, and conical or pyramidal holes were formed on the surface of the transparent conductive layer.

There is also a method of forming a conical or pyramid-shaped hole by etching in a gas phase or a liquid phase after forming a transparent conductive layer.

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

When the reaction is carried out in a liquid phase, examples of the acid include
Sulfuric acid, hydrochloric acid, nitric acid, carbonic acid, phosphoric acid, hydrofluoric acid, chromic acid,
Sulfamic acid, oxalic acid, tartaric acid, citric acid, formic acid,
Lactic acid, glycolic acid, acetic acid, gluconic acid, succinic acid, malic acid, etc., or those diluted with water, or a mixture thereof can be used. Examples of the alkali include caustic soda, ammonium hydroxide,
Potassium hydroxide, sodium carbonate, sodium bicarbonate, sodium sesquicarbonate, first sodium phosphate, second sodium phosphate, third
Sodium phosphate, sodium pyrophosphate, soda polyphosphate, sodium tetrapolyphosphate, sodium trimetaphosphate,
Sodium tetrametaphosphate, sodium hexametaphosphate, sodium orthosilicate, sodium metasilicate, or the like, or a mixture thereof diluted with water or a mixture thereof can be used. When etching is performed in a liquid phase, the etching liquid may be heated or energy such as ultrasonic waves may be applied.

After the etching process, an annealing process may be performed. When performing the annealing treatment, the annealing treatment is performed in an atmosphere of air, water vapor, nitrogen, hydrogen, oxygen, an inert gas or another gas at a temperature and a time suitable for the material of the transparent conductive layer.

(Photoelectric Conversion Layer) As a material of the photoelectric conversion layer used in the present invention, a material using a group IV element such as Si, C, Ge or the like, or a group IV alloy such as SiGe, SiC, SiSn or the like is used. Or a material using a II-VI group element such as CdS or CdTe, or CuInS
_II such as e ₂ , Cu (InGa) Se ₂ , CuInS ₂
Those using II-VI group elements are used.

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

The photoelectric conversion layer can perform valence electron control and forbidden band width control. Specifically, when forming a photoelectric conversion layer, a raw material compound containing an element serving as a valence electron controlling agent or a forbidden band width controlling agent is used alone, or the deposited film forming raw material gas is mixed with the diluent gas. What is necessary is just to introduce in a film space.

Further, at least a part of the photoelectric conversion layer is doped with p-type and n-type by valence electron control to form at least one pair of pin junctions. By stacking a plurality of pin junctions, a so-called stack cell configuration is obtained.

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

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

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

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

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

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

In the stack type photovoltaic element, the material of the pin-junction i-type semiconductor layer near the light incident side may be a material having a wide band gap, or a p-type material far from the light incident side.
As a material for the in-junction i-type semiconductor layer, a material having a narrow band gap is preferably used. When having three pin junctions, the peak of each absorption wavelength is typically 500 nm, 650 nm, and 750 nm from the light incident side.
Before and after.

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

Further, the photovoltaic device of the present invention
The characteristics of the i-type semiconductor layer include the content of hydrogen atoms.
(C_H) Is 1.0-25.0%, AM1.5, 100
mW / cm^Two Photoconductivity under simulated sunlight irradiation (σp)
But 1.0 × 10^-7S / cm or more, dark conductivity (σd)
But 1.0 × 10^-9S / cm or less, constant photo
Urbach Energy by Current Method (CPM)
But 55 meV or less, and the localized level density is 10¹⁷/ Cm^ThreeLess than
The following are preferably used.

(2) P-type semiconductor layer or n-type semiconductor layer As an amorphous material (denoted as a-) or a microcrystalline material (denoted as μc-) of a p-type semiconductor layer or an n-type semiconductor layer, For example, a-Si: H, a-Si: HX, a-S
iC: H, a-SiC: HX, a-SiGe: H, a-
SiGe: HX, a-SiGeC: H, a-SiGe
C: HX, a-SiO: H, a-SiO: HX, a-S
iN: H, a-SiN: HX, a-SiON: H, a-
SiON: HX, a-SiOCN: H, a-SiOC
N: HX, μc-Si: H, μc-Si: HX, μc −
SiC: H, μc-SiC: HX, μc-SiO: H,
μc-SiO: HX, μc-SiN: H, μc-Si
N: HX, μc-SiGeC: H, μc-SiGeC:
HX, μc-SiON: H, μc-SiON: HX, μ
c-SiOCN: H, μc-SiOCN: HX, etc.
Type valence control agents (Group III atoms B, A in the periodic table)
l, Ga, In, TI) and n-type valence electron control agents (Group V atoms P, As, Sb, Bi) in a high concentration. For example, poly-SiH, poly-S
i: HX, poly-SiC: H, poly-SiC:
HX, poly-SiO: H, poly-SiO: H
X, poly-SiN: H, poly-SiN: HX,
poly-SiGeC: H, poly-SiGeC: H
X, poly-SiON: H, poly-SiON: H
X, poly-SiOCN: H, poly-SiOC
N: HX, poly-SiON: H, poly-SiO
N: HX, poly-Si, poly-SiC, pol
y-SiO, poly-SiN, etc., a p-type valence electron controlling agent (Group III atom B, Al, Ga, In,
TI) and n-type valence electron controlling agents (Group V atoms in the periodic table)
P, As, Sb, Bi) may be added at a high concentration.

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

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

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

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

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

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

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

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

When the deposition is performed by the RF plasma CVD method, the substrate temperature in the deposition chamber is 100 to 350 ° C., the internal pressure is 0.1 to 10 torr, and the RF power is 0.001 to 1.0.
5.0 W / cm ² , the deposition rate is 0.1 to 30 ° / sec.
c is mentioned as a suitable condition.

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

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

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

Elements that expand the band gap of the i-type semiconductor layer used for forming the first p-type semiconductor layer of the photovoltaic device of the present invention include carbon, oxygen, nitrogen and the like.

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

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

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

As a substance to be introduced into the p-type layer or the n-type layer for controlling valence electrons, there can be mentioned a Group III atom and a Group III atom of the periodic table.

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

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

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

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

(Transparent Electrode) In the present invention, the transparent electrode 10
Reference numeral 7 denotes an electrode on the light incident side that transmits light, and also functions as an anti-reflection film by optimizing the film thickness. The transparent electrode 107 is required to have high transparency in a wavelength region where the semiconductor layer can absorb light and to have low resistivity. Preferably, the transmittance at a wavelength of 550 nm or more is 80% or more, more preferably 8% or more.
It is desirable that it be 5% or more. Further, the resistivity is preferably 5 × 10 ⁻³ Ω / cm or less, more preferably 1 × 10 ⁻³ Ω / cm.
It is desirable that it is 10 ⁻³ Ω / cm or less. The materials include In ₂ O ₃ , SnO ₂ , and ITO (In ₂ O ₃ + Sn
O ₂ ), ZnO, CdO, Cd ₂ SnO ₄ , TiO ₂ , Ta
A conductive oxide such as ₂ O ₅ , Bi ₂ O ₃ , MoO ₃ , and Na _x WO ₃ or a mixture thereof is suitably used.
Further, an element (dopant) that changes the conductivity may be added to these compounds.

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

The surface of the transparent electrode 107 (that is, the surface of the photovoltaic element excluding the surface protective layer) may be flat, but the surface of the transparent electrode 107 may be flat on the surface of the transparent conductive layer. It is more desirable that conical or pyramidal holes corresponding to the conical or pyramidal holes are formed dispersed over the entire surface. As a result, light scattering on the light incident side of the photovoltaic element, particularly on the interface between the semiconductor layer and the upper transparent electrode, is promoted, and light is scattered on both the light incident side and the back side of the semiconductor layer. , The optical path length in the semiconductor layer further increases, the light absorption increases, and the short-circuit current (Js
c) was further increased.

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

(Current Collecting Electrode) In the present invention, the current collecting electrode 1
08 is formed on a part of the transparent electrode 107 as necessary when the resistivity of the transparent electrode 107 cannot be sufficiently reduced;
It functions to lower the resistivity of the electrode and lower the series resistance of the photovoltaic element. Examples of the material include metals such as gold, silver, copper, aluminum, nickel, iron, chromium, molybdenum, tungsten, titanium, cobalt, tantalum, niobium, and zirconium; alloys such as stainless steel; and powdered metals. Paste and the like. Then, the shape is formed in a branch shape as shown in FIG. 4, for example, so as not to block incident light on the semiconductor layer as much as possible.

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

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

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

[0093]

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

Example 1 (Optimal value of diffuse reflectance) A back reflection layer was formed on a stainless steel plate.
A pin-type photovoltaic element having the configuration shown in FIG. 1 was prepared using the substrate having the transparent conductive layer formed thereon as a substrate.

First, the production was performed from the substrate.

As shown in Table 1-1, the stainless steel slab after the rolling treatment was subjected to various surface treatments such as photo-annealing or annealing pickling, etching treatment, skin pass treatment, polishing treatment, and ultrasonic treatment with acid. It is appropriately selected and processed so as to obtain a shape, and has a thickness of 0.15 mm and 50 × 5 shown in Table 1-1.
It was processed into a 0 mm ² SUS plate (not shown).

First, the back surface reflection layer shown in Table 1-1 was formed using the sputtering apparatus shown in FIG. The acid-treated stainless steel plate 502 is added to the heater 503 in FIG.
And the deposition chamber 501 was evacuated from the exhaust port to which the oil diffusion pump was connected. Table 1 shows the temperature of the stainless steel plate.
When the temperature reached 1 and the pressure reached 1 × 10 ⁻⁶ Torr, the valve 514 was opened, and the mass flow controller 516 was adjusted to supply Ar gas at 10 to 50 sccm.
The pressure was adjusted by the conductance valve 513 so that the pressure became 3 to 10 mTorr. Power supply 506 to -3
DC power of 50-450 V or RF power of 200-500 W was applied to the target 504 to generate Ar plasma.

The target shutter 507 was opened to form a surface reflection layer having a thickness of 50 to 100 nm as shown in Table 1-1 on the surface of the stainless steel plate. When the surface reflection layer was formed, the shutter was closed to extinguish the plasma, thereby completing the production of the rear surface reflection layer. .

Further, a plurality of samples were obtained by appropriately changing the parameters. A part of the substrate on which the back reflection layer was formed was measured for diffuse reflectance. An integrating sphere is used for measuring the diffuse reflectance. Light incident from the opening of the integrating sphere is reflected by a substrate having a back reflection layer provided in the opening opposite to the integrating sphere. Light specularly reflected inside the integrating sphere is absorbed by the black body. The diffusely reflected light reaches a spectrophotometer (Hitachi U40co) provided above the integrating sphere and has a wavelength of 800 nm.
Is measured. The ratio between the intensity of the diffusely reflected light and the intensity of the incident light is the diffuse reflectance.

First, an Ar gas is introduced into the deposition chamber at 4 to 40 sccm, and the substrate temperature is set at 200 to 45
0 ° C., pressure 5-20 mTorr, sputtering power supply 51
0 to -350 to -450 V DC power or 100 to
400 W of RF power was applied to the ZnO target 508 to generate Ar plasma.

When the target shutter 511 was opened and a ZnO thin film layer having a thickness of 0.5 to 2.0 μm was formed on the reflective layer surface, the shutter was closed to extinguish the plasma. Further, a plurality of samples were obtained by appropriately changing parameters.

The transparent conductive layer thus obtained is shown in Table 1.
In the case where the surface was further etched as shown in -1, the etching was performed as follows.

First, the substrate 522 formed up to the transparent conductive layer is brought into close contact with the heater 521 of the etching apparatus shown in FIG.
20 was evacuated. The temperature of the stainless steel plate was stabilized at a desired temperature, and when the pressure reached 1 × 10 ⁻⁶ Torr, the valve 524 was opened and the mass flow controller 53 was opened.
2,533 was adjusted and the etching gas was 5-100sc
cm, and the pressure was adjusted with a conductance valve 523 so that the pressure became 1 to 20 mTorr. DC power of -350 to -450 V from power supply 526 or 2
An RF of 00 to 500 W was applied to generate plasma.

After maintaining the plasma for a desired period of time, the plasma was extinguished, and the surface treatment of the back reflection layer was completed. Further, a plurality of samples were obtained by appropriately changing parameters.

At the stage when the transparent conductive layer was formed, a part of each substrate was observed for its surface shape by an electron microscope (SEM). As a result, a sample having a conical or pyramidal hole as shown in FIG. 3 was obtained.

Next, an n-layer, an i-layer, and a p-layer were sequentially formed on the ZnO thin film layer by a multi-chamber separation type deposition apparatus shown in FIG. a-
The n layer made of Si and the p layer made of μc-Si are RFP
An i-layer made of a-Si formed by a CVD method is RFPCV
It was formed by the D method and the MWPCVD method. The production procedure was performed as follows.

First, all the transport systems and the deposition chambers were set at 10 ⁻⁶ T.
Vacuum was applied to the orr table. The substrate was set on the substrate holder 690 and placed in the load lock chamber 601. The load lock chamber was evacuated to a vacuum of the order of 10 ^-3 Torr with a mechanical booster pump / rotary pump (not shown), and switched to a turbo molecular pump to evacuate the pressure to the order of 10 ^-6 Torr. Open the gate valve 606 and set the substrate holder 6
90 was transferred to the n-type layer transfer chamber 602. Gate valve 6
06 is closed. The substrate was moved under the substrate heating heater 610, and a hydrogen gas was flowed to make the pressure substantially the same as the pressure at the time of film formation. The substrate was heated to a temperature shown in Table 1-1 by the substrate heating heater 610 and stabilized. Mass flow controller 63
6-639, Stop Balf 630-634, 641-
Source gas shown in Table 1-1 for n-type layer deposition was supplied to the deposition chamber via 644. RF power shown in Table 1-1 was supplied from the RF power supply 622 to the RF introduction cup 620. An n-type layer having a thickness shown in Table 1-1 was deposited for a desired deposition time. The supply of the source gas for n-type layer deposition was stopped, and the gas was evacuated to a degree of vacuum of the order of 10 ^-6 Torr by a turbo molecular pump. The substrate heating heater 610 is raised, the gate valve 607 is opened, and the substrate holder is set to MW-i or RF-i.
After moving to the transfer chamber 603, the gate valve 607 was closed. The substrate is transferred under the heater 611 for substrate heating,
After lowering the substrate heating heater 611 to heat and stabilize the substrate to the substrate temperature shown in Table 1-1, the RF-i layer was deposited. The RF-i layer is supplied to the deposition chamber 618 through the MW-i or RF-i layer deposition gas supply equipment (gas supply pipe 649, stop valves 650 to 655, 661 to 665, and mass flow controllers 656 to 660). i
Source gases shown in Table 1-1 for layer deposition were supplied. RF-
The evacuation pump was used to adjust the degree of vacuum shown in Table 1-1 for i-layer deposition. R (not shown) is applied to the bias application electrode 628.
Introduce desired RF power from F power source and RF plasma CV
An RF-i layer was deposited on the n-type layer at a layer thickness shown in Table 1-1 by Method D. The supply of the source gas was stopped, and the inside of the deposition chamber was evacuated to a level of 10 ^-6 Torr by a turbo-molecular pump. At the same time, the substrate temperature was set and maintained at a temperature shown in Table 1-1 suitable for the deposition of the MW-i layer. Table 1 suitable for deposition of MW-i layer
-1 was supplied to the deposition chamber 618 from a gas supply facility for MW-i or RF-i layer deposition. The degree of vacuum in the deposition chamber was maintained at the degree shown in Table 1-1 by an exhaust device such as a diffusion pump (not shown). MW power shown in Table 1-1 was introduced into the deposition chamber 618 from a MW power supply (not shown). At the same time, an RF power source (not shown) is connected to the bias electrode 628 according to Table 1
The bias power shown in FIG. The shutter 650 is opened and M is applied on the substrate by the microwave plasma CVD method of the present invention.
A Wi layer was deposited. Thereafter, the source gas shown in Table 1-1 suitable for the deposition of the MW-i layer is supplied from the gas supply equipment for MW-i or RF-i layer deposition to the deposition chamber 618 to form the MW-i layer having a predetermined thickness. After that, the shutter was closed, the MW power and the like were stopped, and the supply of the raw material gas was stopped. The inside of the deposition chamber 618 was evacuated to 10 ⁻⁶ Torr by a turbo molecular pump. RF on the MW-i layer in the same manner as the deposition of the RF-i layer.
-I layer was deposited under the conditions shown in Table 1-1. After deposition of the RF-i layer, the deposition chamber was evacuated to the order of 10 ^-6 Torr. The substrate heating heater 611 is separated from the substrate, and the gate valve 6
08 and open the substrate holder 690 to the p-type layer transfer chamber 604.
Move to The gate valve 608 is closed, and the substrate is moved under the heater 612 for substrate heating.
The substrate temperature is set to -1 and stabilized. H ₂ gas was supplied under the conditions shown in Table 1-1, and RF power shown in Table 1-1 was introduced into the deposition chamber 619 to generate hydrogen plasma. After terminating the hydrogen plasma treatment, the gas supply equipment for the p-type layer deposition (stop valves 670 to 674, 681 to 681)
684, a p-type layer deposition gas was supplied to the deposition chamber 619 from the mass flow controllers 676 to 679). The degree of vacuum in the deposition chamber was adjusted to a degree shown in Table 1-1 by an exhaust pump (not shown). RF into cup 621 for RF introduction
The power shown in Table 1-1 was introduced from the power supply 623, and a p-type layer was deposited to a thickness shown in Table 1-1 by the RF plasma CVD method. As described above, the pin structure is formed on the substrate.

Next, after stopping the flow of the gas and continuing the flow of the H ₂ gas for 5 minutes, the flow of the H ₂ gas was stopped, and the deposition chamber and the gas pipe were evacuated to 1 × 10 ^-5 Torr.
The substrate was moved to the unload chamber 605. After sufficiently cooling the substrate, it was taken out.

Next, a transparent electrode was formed on the p-layer as shown in Table 1
Indium oxide shown in No. 1 was vacuum-deposited by a resistance heating vacuum deposition method. Then, a mask having a comb-shaped hole is placed on the transparent electrode, and as shown in Table 1-1, a comb-shaped current collecting electrode (FIG. 4) made of Cr / Ag / Cr is vacuum-evaporated by electron beam vacuum evaporation. Evaporated. Thus, the fabrication of the photovoltaic device having the configuration shown in FIG. 1 has been completed.

[0110]

[Table 1]

First, the results of the measurement of diffuse reflectance on the substrate on which the back metal reflection layer is formed will be described.

The value of the diffuse reflectance ranged from 1% to 55% depending on the surface treatment on the stainless steel plate and the conditions for forming the reflective layer.

It has been found that the surface of the transparent conductive layer can take various shapes depending on the shape of the stainless steel surface, the material and shape of the reflective layer, the thickness of the transparent conductive layer, the deposition rate, the forming temperature, and the like. Among them, focusing on the conical or pyramid-shaped holes, the holes were classified into those present on the surface and those not present.

Next, with regard to the photovoltaic elements prepared in Example 1, three pieces were prepared for each substrate, and all the photovoltaic elements were further divided into 10 subcells. The efficiency (photovoltaic power / incident optical power) was measured. Subsequently, a light deterioration test and a high temperature / high humidity reverse bias (HHRB) deterioration test were performed.

{Circle around (1)} The initial photoelectric conversion efficiency can be measured by installing a photovoltaic device under AM-1.5 (100 mW / cm ² ) light irradiation and measuring V-1 characteristics.

(4) The photodegradation was measured by measuring the initial photoelectric conversion efficiency of a photovoltaic element at a humidity of 50% and a temperature of 5%.
After installing in an environment of 0 ° C. and irradiating AM-1.5 light for 500 hours, the rate of decrease in photoelectric conversion efficiency under AM1.5 light irradiation (photoelectric conversion efficiency after light degradation test / initial photoelectric conversion efficiency) Was performed.

(4) The measurement of high temperature and high humidity reverse bias (HHRB) degradation is performed by installing a photovoltaic element whose initial photoelectric conversion efficiency has been measured in advance in a dark place at a temperature of 80 ° C. and a humidity of 80%. Then, a reverse bias of 0.7 V was applied and the voltage was held for 200 hours. Thereafter, the rate of decrease in photoelectric conversion efficiency (HHRB) under AM1.5 light irradiation (photoelectric conversion efficiency after deterioration test / initial photoelectric conversion efficiency) was performed.

The results are shown in FIG. 8-1, FIG. 8-2, FIG.
-3. The numerical values are normalized on an arbitrary scale.

As a result of the measurement, good initial conversion efficiency was obtained when a substrate having conical or pyramidal holes was used and when the diffuse reflectance on the back reflection layer was 3% or more and 50% or less. Was done. This is mainly the open circuit voltage (Voc),
This is due to the improvement of the fill factor (FF). On the other hand, when a substrate having no conical or pyramid-shaped hole was used, the value was generally lower than in the case where a hole was present.

Next, regarding the conversion efficiency after the light deterioration test, when there is a hole, the case where the diffuse reflectance on the back reflection layer is 3% or less or 50% or more compared to the case where the diffuse reflectance is 3% or more and 50% or less. Was low. This is considered to be caused by an increase in series resistance due to peeling for diffuse reflectance of 3% or less, and to a decrease in shunt resistance due to texture structure for diffuse reflectance of 50% or more.

Regarding the conversion efficiency after the HHRB deterioration test, the same result as the measurement result after the light deterioration test was obtained.

As described above, the light of the present invention using the substrate in which the diffuse reflectance of the surface of the back reflection layer is 3% or more and 50% or less and the conical or pyramid-shaped holes are dispersedly formed in the surface of the transparent conductive layer. It has been found that the electromotive element has better characteristics than the conventional photovoltaic element.

Example 2 (Optimal values of d, C ₁ , C ₂ ) The processing conditions of the SUS plate used in Example 1, the formation conditions of the back metal reflection layer, and the manufacturing conditions of the transparent conductive layer, A condition in which the diffuse reflectance of the surface of the metal reflective layer is 3% or more and 50% or less, and a conical or pyramid-shaped hole is present on the transparent conductive layer is selected. The condition is further subdivided, and another processing method is added. A photovoltaic device having the configuration shown in FIG. 1 was formed on a substrate (not shown) having a thickness of 0.20 mm and 50 × 50 mm ² shown in Table 2-1 in the same manner as in Example 1 on the substrate. An element was manufactured.

First, the production was performed from the substrate.

The stainless slab was treated under various conditions as shown in Table 2-1 and then subjected to a process such as surface etching and polishing. Next, as in the first embodiment, FIG.
The back metal reflective layer and the transparent conductive layer were formed under the conditions shown in Table 2-1 using the sputtering apparatus shown in Table 1.

For a part of the substrate up to the transparent conductive layer, the surface of the conductive layer was etched under the conditions shown in Table 2-1 in the same manner as in Example 1.

A part of the substrate after the above steps was left for evaluation, and the other substrates were formed with semiconductor layers under the conditions shown in Table 2-1 in the same manner as in Example 1.

Thereafter, the substrate was subjected to the CVD system as shown in Table 2-1.
A pin-type semiconductor layer, an In ₂ O ₃ transparent electrode, and a current collecting electrode were formed under the conditions shown in (1) to produce a photovoltaic element.

[0129]

[Table 2]

For the photovoltaic element, the substrate under each condition was manufactured, and the substrate was further divided into ten subcells. The yield, the initial photoelectric conversion efficiency were examined, the adhesion test, the high temperature and high humidity reverse bias (HHRB) were performed. Each test of deterioration and deterioration of temperature and humidity was performed.

In the adhesion test, 10 cuts were made on the photovoltaic element at intervals of 1 mm in a grid pattern.
After attaching 0 squares, the cellophane adhesive tape was adhered, and after sufficient adhesion, it was instantaneously peeled off, and the area of the peeled portion was evaluated.

{Circle around (2)} The temperature and humidity cycle deterioration is measured by measuring the initial photoelectric conversion efficiency of a photovoltaic element at a temperature of 80 ° C.
Installed in a dark place at 80 ° C and 80% humidity and kept for 4 hours, then about 9
The temperature is lowered to −30 ° C. over 0 minutes, held for 30 minutes, and returned to 80 ° C. and 80% humidity again over 90 minutes. After repeating this cycle 15 times, the reduction rate of the photoelectric conversion efficiency under AM1.5 light irradiation (photoelectric conversion efficiency after temperature / humidity cycle deterioration test / initial photoelectric conversion efficiency) was performed.

First, in the same manner as in Example 1, the surface shape of the substrate which had been subjected to the steps immediately before the preparation of the semiconductor layer was observed, and a conical or pyramidal hole was formed using a stylus type surface roughness measuring instrument. The average diameter was determined as d (μm), the average depth was determined as h (μm), and the coefficient C1≡h / d was determined. Also, when surface observation was performed, the number of conical or pyramidal holes within the range of 50 × 50 μm was checked and the average density ρ
And a coefficient C2≡ρ × d ² was determined.

As a result, the average diameter d of the cone or pyramid
Was 0.03 to 5 μm.

First, a coefficient C1 is set for a conical or pyramidal hole having an average diameter of 0.03 to 5 μm.
Regardless of the values of C2 and C2, the characteristics of the photovoltaic element were examined for each of the above items.

Table 2-2 shows the results. The numerical values are standardized values in each item.

As a result, all of the conical or pyramid-shaped holes having an average diameter in the range of 0.05 μm to 2 μm were excellent, while the average diameter of the conical or pyramid-shaped holes was 0.05 μm.
Those having a diameter of less than μm were deteriorated in characteristics as in the case where no conical or pyramid-shaped holes were present, due to an increase in series resistance caused by peeling due to adhesion. In the case of a conical or pyramid-shaped hole having an average diameter of more than 2 μm, the characteristics decreased due to the decrease in Jsc.

Based on the above results, the coefficients C1 and C2 were examined from substrates having a conical or pyramidal average diameter in the range of 0.05 μm to 2 μm.

As a result, the coefficient C1 was in the range of 0.1 to 1.5, and the coefficient C2 was in the range of 0.01 to 1.5.

Then, the initial photoelectric conversion efficiency of the photovoltaic element formed on the substrate having the coefficient in these ranges was examined in the same manner as described above, and the high-temperature high-humidity reverse bias (HHR) was measured.
B) Each test of deterioration and deterioration of temperature and humidity was performed to examine the characteristics.

The results are shown in Tables 2-3, 2-4 and 2-5.
Shown in The numerical values are standardized values in each item.

As a result, when the coefficient C1 is in the range of 0.2 to 0.9 and the coefficient C2 is in the range of 0.02 to 1.0, all the characteristics are excellent. 2
Alternatively, when C2 is smaller than 0.02, a decrease in characteristics due to a decrease in Jsc is observed.
Alternatively, when it is larger than 1.0, the characteristics are lowered due to the reduction of Voc and FF.

As described above, according to the present invention, the conical or pyramid-shaped average diameter d is from 0.05 μm to 2.0 μm, the coefficient C1 is from 0.2 to 0.9, and C2
It has been found that a photovoltaic element using a substrate having a value of 0.02 to 1.0 has excellent characteristics.

[0144]

[Table 3]

[0145]

[Table 4]

[0146]

[Table 5]

[0147]

[Table 6]

Example 3 (Optimal Value of Diffuse Reflectance / Roll-to-Roll Manufacturing Method) In the same manner as in Example 1, a stainless steel plate was treated with a length of 100 m, a width of 30 cm, and a thickness of 0.13 mm. Table 3-1
Using the belt-shaped SUS sheet shown in FIG.
The triple type solar cell of FIG. 2 was produced using a deposition apparatus using a roll method.

First, the SUS sheet was rolled to 0.13 mm by a rolling device, and after the treatment as shown in Table 3-1 was completed, the back metal was roll-to-rolled under the conditions shown in Table 3-1. After forming the reflective layer, a part of the substrate was evaluated for reflectance in the same manner as in Example 1, and the other substrate was formed with a transparent conductive layer by a roll-to-roll method, and if necessary, the surface of the transparent conductive layer was formed. The processing was performed.

A part of the substrate having been subjected to the steps up to this point is left for substrate surface observation, and the other substrate is formed with a photovoltaic device under the conditions shown in Table 3-1 by a roll-to-roll CVD apparatus. did.

FIG. 7A is a schematic view of an apparatus for continuously forming photovoltaic elements using the roll-to-roll method. This apparatus includes a substrate delivery chamber 710 and a plurality of deposition chambers 701 to 701.
13 and a substrate take-up chamber 730 are sequentially arranged and connected between them by a separation passage 714. Each deposition chamber has an exhaust port, and the inside can be evacuated.

The strip-shaped substrate 740 is wound up from the substrate delivery chamber to the substrate winding chamber through these deposition chambers and separation passages. At the same time, gas is introduced from the gas inlets of the respective deposition chambers and the separation passages, and the gas is exhausted from the respective exhaust ports to form respective layers. A halogen lamp heater (not shown) that heats the substrate from the back is installed in each deposition chamber, and is heated to a predetermined temperature in each deposition chamber. RF electrodes 71 are provided in each deposition chamber.
7 or a microwave applicator 718 is attached, and a source gas supply device (not shown) is connected to an inlet 715 of the source gas. A bias electrode 720 is disposed in the deposition chambers 703 and 707, which are deposition chambers for the MW-i layer, and an RF power supply (not shown) is connected as a power supply. The substrate delivery chamber has a delivery roll 721 and a guide roller 722 for applying an appropriate tension to the substrate and always keeping the substrate horizontal. The substrate take-up chamber has a take-up roll 723 and a guide roller 724.

FIG. 7B is a top view of the deposition chambers 701 to 713. Each deposition chamber has a raw material gas inlet 715 and an exhaust port 716, and the exhaust port includes an oil diffusion pump and a mechanical booster pump. A vacuum pump (not shown) is connected.

First, the SUS430BA sheet is wound around a delivery roll 721 (average radius of curvature 30c).
m), the substrate is set in the substrate delivery chamber 710, and after passing through each deposition chamber, the end of the substrate is wound around the substrate take-up roll 723. The entire device is evacuated with a vacuum pump,
The lamp heater in each deposition chamber is turned on to set the substrate temperature in each deposition chamber to a predetermined temperature. When the pressure of the entire apparatus becomes 1 mTorr or less, the inlet 7 of the scavenging gas
From 19, a scavenging gas as shown in FIG. 7A flows in, and the substrate is taken up by a take-up roll while moving the substrate in the direction of the arrow in the figure. Each source gas flows into each deposition chamber. At this time, the flow rate of the gas flowing into each separation passage or the pressure of each deposition chamber is adjusted so that the raw material gas flowing into each deposition chamber is not diffused into another deposition chamber. Then R
F power, or MW power and RF bias power are introduced to generate plasma, and the first p is applied under the conditions shown in Table 6-1.
The n1 layer in the deposition chamber 701 as the in-junction, the deposition chamber 702,
The i1 layer is deposited in 703 and 704, the p1 layer is deposited in the deposition chamber 705, and the n2 layer is deposited as the second pin junction in the deposition chamber 706, the i2 layer is deposited in the deposition chambers 707, 708, and 709, and the p2 layer is deposited in the deposition chamber 710. , Deposition chamber 711 as third pin junction
Is the n3 layer, the deposition chamber 712 is the i3 layer, and the deposition chamber 713 is p3.
Layers were deposited to form a photovoltaic device consisting of three layers of pin junctions.

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

Next, a transparent electrode 213 was formed on a three-layer pin junction using a reactive sputtering apparatus under the conditions shown in Table 3-1.

Next, a wire grid composed of a silver clad layer and a carbon layer using a urethane resin as a binder is formed around the copper wire on the transparent electrode 213 by heating and fusion to form a current collecting electrode. 250m solar cell
It was cut into a size of mx 100 mm.

The fabrication of the triple solar cell using the roll-to-roll method has been completed.

[0159]

[Table 7]

First, the results of the measurement of diffuse reflectance on the substrate on which the back metal reflection layer is formed as in Example 1 will be described.

The value of the irregular reflectance was in the range of 2% to 55% depending on the surface treatment on the stainless steel plate and the material of the reflective layer.

As in the case of Example 1, the surface of the transparent conductive layer can take various shapes depending on the shape of the stainless steel surface, the material and shape of the reflective layer, the thickness and the deposition rate of the transparent conductive layer, the forming temperature, and the like. all right. Similarly to Example 1, attention was paid to holes in the shape of a cone or a pyramid, and the holes were classified into those having a hole on the surface and those not having the hole.

Next, with respect to the photovoltaic elements prepared in Example 3, three pieces were prepared for each substrate, and all the photovoltaic elements were further divided into ten subcells. Conversion efficiency (photovoltaic power / incident optical power)
Was measured. Subsequently, a light deterioration test and a high temperature / high humidity reverse bias (HHRB) deterioration test were performed.

The results are shown in FIGS.
-3. The numerical values are normalized on an arbitrary scale.

As a result of the measurement, as in the case of Example 1, when a substrate having a conical or pyramid-shaped hole was used, the diffuse reflectance on the back reflection layer was 3% or more and 50% as in Example 1.
Good characteristics were obtained in the following cases. This is mainly due to improvements in open circuit voltage (Voc) and fill factor (FF). When a substrate having no conical or pyramid-shaped hole was used, the value was generally lower than that in the case where a hole was present.

Next, regarding the conversion efficiency after the light deterioration test, when there is a hole, the case where the diffuse reflectance on the back reflection layer is 3% or less or 50% or more compared with the case where the diffuse reflectance is 3% or more and 50% or less. Was low. This is considered to be caused by an increase in series resistance due to peeling for diffuse reflectance of 3% or less, and to a decrease in shunt resistance due to texture structure for diffuse reflectance of 50% or more.

Regarding the conversion efficiency after the HHRB deterioration test, the same result as the measurement result after the light deterioration test was obtained.

As described above, the light using the substrate in which the diffuse reflectance of the surface of the back reflection layer of the present invention is 3% or more and 50% or less and the conical or pyramidal holes are dispersedly formed in the surface of the transparent conductive layer. It has been found that the electromotive element has better characteristics than the conventional photovoltaic element.

Example 4 A pin type solar cell of FIG. 1 was produced in the same manner as in Example 1 except that the back reflection layer was changed from Al to Cu.

The diffuse reflectance values ranged from 2% to 70%.

When the initial photoelectric conversion efficiency, the conversion efficiency after the light deterioration test, and the conversion efficiency after the HHRB deterioration test were measured in the same manner as in Example 1, the diffuse reflectance of the back reflection layer surface was 3%.
% Or more and 50% or less, a photovoltaic device using a substrate in which conical or pyramid-shaped holes are dispersedly formed on the surface of the transparent conductive layer may have characteristics superior to those of a conventional photovoltaic device. Do you get it.

Example 5 The back reflection layer was changed from Al to AlS.
i (10 to 100 nm, substrate temperature RT to 100 ° C.) and Al (50 to 100 nm, substrate temperature RT to 150 ° C.) except that the two-layer configuration was changed to the same as in Example 1 except that p in FIG.
An in-type solar cell was produced.

The values of the diffuse reflectance ranged from 1% to 75%.

When the initial photoelectric conversion efficiency, the conversion efficiency after the light deterioration test, and the conversion efficiency after the HHRB deterioration test were measured in the same manner as in Example 1, the diffuse reflectance of the back reflection layer surface was 3%.
% Or more and 50% or less, a photovoltaic device using a substrate in which conical or pyramid-shaped holes are dispersedly formed on the surface of the transparent conductive layer may have characteristics superior to those of a conventional photovoltaic device. Do you get it.

[0175]

According to the first to fourteenth aspects of the present invention, the following effects can be obtained.

The adhesion between the back reflection layer and the transparent conductive layer was improved by a moderately rough surface. On the other hand, unlike the pyramid-type texture structure, the contact area between the back reflection layer and the transparent conductive layer does not become excessive, so that the diffusion (migration) of metal in the back reflection layer can be suppressed, and the metal and the components of the transparent conductive layer can be mixed. The reaction was suppressed, and a decrease in reflectance was prevented. This effect is remarkable in the case of aluminum which is suitably used as a back reflection layer. In addition, compared with the case where the back reflection layer is a mirror surface, the light that has arrived is diffusely reflected, so that the optical path length is extended, and the incident light can be used effectively.

As a result, the series resistance was reduced, the leak current was reduced, the short circuit current, the open circuit voltage, and the fill factor were improved, and high conversion efficiency was obtained. In addition, the controllability and flexibility of the manufacturing process were improved, and at the same time, a high yield was maintained. In addition, as a result of a high-temperature high-humidity cycle test, a salt water test, and the like, the weather resistance was improved. In addition, as a result of a mechanical strength test such as a scratch test and a bending test, the durability was improved.

The use of stainless steel for the substrate facilitated the formation of the backside reflection layer having a preferable diffuse reflectance.

Since holes are also formed on the surface of the photovoltaic element, light scattering at the interface between the photoelectric conversion layer and the upper transparent electrode is promoted, and the light is incident on the light incident side of the photoelectric conversion layer. Light was scattered on both sides of the back surface, the optical path length in the photoelectric conversion layer was further extended, light absorption was increased, and the short-circuit current was further increased.

Further, by using zinc oxide as the transparent conductive layer, the transparent conductive layer has an appropriate resistance value, and the current flowing in the defect region of the photoelectric conversion layer decreases, so that the photovoltaic element shunts. And the production yield improved. In addition, due to the C-axis orientation of zinc oxide, it became easy to form conical or pyramidal holes on the surface.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a layer configuration of a photovoltaic device of the present invention.

FIG. 2 is a diagram illustrating an example of a layer configuration of the photovoltaic element of the present invention.

FIG. 3 a. b. c. d is an example of an electron micrograph of the transparent conductive layer thin film on the substrate of the photovoltaic device of the present invention.

FIG. 4 is a view showing a collecting electrode of the photovoltaic element of the present invention.

FIG. 5A is a view schematically showing a sputtering apparatus suitable for depositing a back reflection layer of the photovoltaic device of the present invention. b is a diagram schematically showing an etching apparatus suitable for processing the back reflection layer of the photovoltaic device of the present invention.

FIG. 6 is a view schematically showing a deposited film forming apparatus suitable for producing a photovoltaic element of the present invention.

FIG. 7A is a diagram schematically showing a roll-to-roll type deposited film forming apparatus suitable for producing a photovoltaic element of the present invention. FIG. 1B is a schematic view of a roll-to-roll type deposited film forming apparatus suitable for producing the photovoltaic device of the present invention as viewed from above.

FIG. 8 is a graph showing the relationship between the initial conversion efficiency and the diffuse reflectance in the present invention used in Example 1 and the conventional photovoltaic device. 2 is a graph showing the relationship between the efficiency and the diffuse reflectance after the photodegradation test in the present invention and the conventional photovoltaic element used in Example 1, and FIG. 3 is Example 1
In the present invention used in the above and the conventional photovoltaic device.
It is a graph showing the relationship between the efficiency after HRB degradation test, and diffuse reflectance.

FIG. 9 is a graph showing the relationship between the initial conversion efficiency and the diffuse reflectance in the present invention used in Example 3 and a conventional photovoltaic element. 2 is a graph showing the relationship between the efficiency and the diffuse reflectance after the photodegradation test in the present invention and the conventional photovoltaic device used in Example 3, and FIG. 3 is Example 3
In the present invention used in the above and the conventional photovoltaic device.
It is a graph showing the relationship between the efficiency after HRB degradation test, and diffuse reflectance.

[Explanation of symbols]

101, 201 substrate 102, 202 back metal reflective layer 103, 203 transparent conductive layer 104, 204, 207, 210 n-type semiconductor layer 105, 205, 208, 211 i-type semiconductor layer 106, 206, 209, 212 p-type semiconductor layer 107, 213 Transparent electrode 108, 214 Current collecting electrode 501, 520 Processing chamber 502, 522 Substrate 503, 521 Heater 504, 508 Target 506, 510, 526 Power supply 525 Electrode 507, 511 Shutter 512, 529 Pressure gauge 513, 523 Conductance valve 514, 515, 524, 527, 528, 530, 5
31 Supply valve 516, 517, 532, 533 Mass flow controller 600 Deposition device 601 Load lock chamber 602, 603, 604 Transfer chamber 605 Unload chamber 606, 607, 608, 609 Gate valve 610, 611, 612 Substrate heater 613 Substrate transport Rails 631-634, 641-644, 651-655, 6
61 to 666, 671 to 674, 681 to 684 Stop valve 636 to 639, 656 to 660, 676 to 679 Mass flow controller 617, 618, 619 Deposition chamber 620, 621 electrode 622, 623, 624 RF power supply 628 Bias electrode 649 Gas supply Pipe 650 Shutter 729 Delivery chamber 730 Winding chamber 701-713 Deposition chamber 714 Separation passage 715 Source gas inlet 716 Exhaust port 717 RF electrode 718 Microwave applicator 719 Scavenging gas inlet 720 Bias electrode 721 Feeding roll 722, 724 Winding roller 723 roll

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-7-122764 (JP, A) JP-A-5-218469 (JP, A) JP-A-7-263729 (JP, A) JP-A 9-1997 293892 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 31/04 H01L 31/042

Claims (11)

(57) [Claims] 1. A photovoltaic device comprising at least a substrate, a back reflection layer, a transparent conductive layer, and a photoelectric conversion layer containing silicon and germanium sequentially laminated, wherein the surface of the substrate and / or the back reflection layer has a mirror surface. And no pyramid-shaped irregularities are formed.
nm, has an appropriate surface roughness of 3% or more and 50% or less, and a wavelength of 650 nm of the transparent conductive layer.
A photovoltaic device, wherein the light transmittance is 80% or more. 2. The photovoltaic device according to claim 1, wherein the transparent conductive layer has a conical or pyramid-shaped hole on a surface thereof. 3. The photovoltaic device according to claim 2, wherein said transparent conductive layer contains zinc oxide. 4. The photovoltaic device according to claim 1, wherein said substrate is made of stainless steel. 5. The photovoltaic device according to claim 1, wherein the back reflection layer is made of gold, silver, copper, aluminum, magnesium or an alloy containing these metals as a main component. 6. The photovoltaic device according to claim 1, wherein said back reflection layer further contains silicon. 7. The photovoltaic device according to claim 1, wherein said back reflection layer has a structure in which a plurality of layers are stacked. 8. The photovoltaic device according to claim 2, wherein a hole is further formed on the surface of the photoelectric conversion layer. 9. The photovoltaic device according to claim 1, wherein the photoelectric conversion layer has a plurality of pin junctions. 10. The photovoltaic device according to claim 1, wherein at least the pin junction closest to the substrate among the plurality of pin junctions contains germanium. 11. The photovoltaic device according to claim 1, wherein the photoelectric conversion layer is made of a non-single-crystal semiconductor.