JP2000349311A - Solar battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve reliability of a solar battery which has high performance and is excellent in mass-productivity, and provide the solar battery at a low cost. SOLUTION: In this solar battery, a lower electrode 4, a photoelectric converting layer 5 and a transparent electrode 6 are arranged in this order on the surface of a metal substrate 2, and an insulating layer 3 exists between the metal substrate 2 and the lower electrode 4. The insulating layer 3 is composed of heat-resistant resin whose glass transition point is at least 260 deg.C and thermal expansion coefficient at 30 to 250 deg.C is 0.1 to 5 times that of the metal substrate 2 at 30 to 250 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a solar cell and a method for manufacturing the same. More specifically, the present invention relates to a solar cell having a photoelectric conversion layer formed on a metal substrate and a method for manufacturing the same.

[0002]

2. Description of the Related Art Solar cells are used in various electronic devices as a power source replacing dry cells and the like. In particular, low power electronic devices such as electronic desk calculators, clocks, portable electronic devices (cameras, mobile phones, consumer radar detectors), remote controllers, etc., can be sufficiently driven by the electromotive force of the solar cell. It has attracted attention because it does not require replacement and can be operated semi-permanently and is environmentally clean. Generally, an amorphous silicon (a-Si) layer or a microcrystalline S
An Si layer such as an i (μc-Si) layer is used.

[0003] A solar cell is constituted by laminating a lower electrode made of metal, a photoelectric conversion layer, and a transparent electrode on a surface of a rigid or flexible substrate. As the substrate, workability,
From the viewpoint of workability and the like, an organic flexible substrate which has flexibility and can be wound up and developed is often used. Usually, a Si layer formed by a plasma CVD method is used as the photoelectric conversion layer.

However, the organic flexible substrate has insufficient heat resistance and is easily deformed by heating, so that the substrate temperature cannot be increased when forming the photoelectric conversion layer. For example, polyethylene naphthalate (PEN), which is often used for organic flexible substrates, has a glass transition point of 113 ° C.
It is about. If the substrate temperature could be increased during plasma CVD, not only would the film deposition rate be improved,
The characteristics of the photoelectric conversion layer are improved.

In addition, when an organic flexible substrate is used, when a photoelectric conversion layer is formed by a plasma CVD method, the substrate is warped, wrinkled, beco, or sagged.
Occurs, and the uniformity of the thickness deteriorates. In addition, "beko" is a common name for a phenomenon in which a film is placed on a flat surface and looks like bekobeko when viewed from the side.

When a pattern is formed using a mask when a plasma CVD film is formed on an organic flexible substrate, the thermal contraction rate during the film formation differs due to the difference in expansion coefficient between the substrate and the plasma CVD film. For this reason, there is a problem that slip deformation occurs and only the patterning portion rises like a drum. Such swelling tends to be more remarkable when a polymer material having a glass transition point (Tg) is used for the substrate. If the patterning portion swells, it becomes difficult to perform positioning, and it becomes difficult to form a multilayer using a mask. In addition, there is also an aesthetic problem that the appearance is poor when applied to a clock or a remote control when there is a climax. Incidentally, if a plasma CVD film is formed on the entire surface of the substrate without performing patterning, such a problem can be avoided.
Since it is necessary to perform patterning by laser processing or the like after the film is formed, the productivity is lower than in the case where patterning is performed simultaneously with the film formation by masking or the like, and the integration processing cost is increased.

As a substrate used for a solar cell, a metal substrate can be used in addition to an organic flexible substrate. Since the metal substrate has better heat resistance than the organic flexible substrate, the temperature of the substrate can be increased when the plasma CVD film is formed. Therefore, the film formation rate and film characteristics are improved. Also, there is no occurrence of “warpage” or the like on the substrate. Further, even if the film is patterned during the plasma CVD, a drum-shaped swell does not occur.

However, since the metal substrate is conductive, if the lower electrode of each cell is provided directly on the metal substrate, both will be short-circuited, making it impossible to integrate a plurality of cells in series. Therefore, it is necessary to form an insulating layer between the lower electrode and the metal substrate. As the insulating layer, a resin layer is conventionally known. Also, in order to suppress the thermal shrinkage of the insulating layer,
There is also known a resin in which fine particles such as TiO ₂ and ZnO are dispersed in a matrix. For example, Japanese Patent Application Laid-Open
JP-A-135817 describes providing an electrical insulator made of polyimide on a metal substrate.

However, according to experiments by the present inventors, when the insulating layer is made of resin, if the metal substrate is heated to a high temperature when forming the photoelectric conversion layer, cracks or pinholes may occur in the insulating layer, It has been found that the insulating layer is easily peeled off from the metal substrate, and as a result, the lower electrode and the metal substrate are short-circuited, thereby lowering the reliability.

[0010]

SUMMARY OF THE INVENTION An object of the present invention is to improve the reliability of a solar cell having high performance and excellent mass productivity, and to provide such a solar cell at low cost.

[0011]

This and other objects are achieved by the present invention which is defined below as (1) to (9). (1) A lower electrode, a photoelectric conversion layer, and a transparent electrode are provided in this order on a surface of a metal substrate, and an insulating layer is present between the metal substrate and the lower electrode. Wherein the glass transition point of the heat-resistant resin is 26
0 ° C. or higher, and 30 to 250 of the heat-resistant resin.
The coefficient of thermal expansion at 30 ° C. is 30 to 250
A solar cell having a coefficient of thermal expansion of 0.1 to 5 times at C. (2) The solar cell according to the above (1), wherein the heat-resistant resin has a coefficient of thermal expansion at 30 to 250 ° C. of 1 × 10 ⁻⁶ to 50 × 10 ⁻⁶ / ° C. (3) The solar cell according to (1) or (2), wherein the insulating layer is a coating film. (4) The solar cell according to any one of (1) to (3), wherein the heat-resistant resin is a polyimide represented by the following formula (1).

[0012]

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(5) The thickness of the insulating layer is 0.1-20.
The solar cell according to any one of the above (1) to (4), which has a size of μm. (6) The metal substrate is made of a metal or an alloy containing at least one of Cu, Al and Ni, or stainless steel, an Fe-Ni alloy and an Fe-Ni-
The solar cell according to any one of the above (1) to (5), which is one type of a Cr alloy. (7) A method for manufacturing a solar cell, wherein the insulating layer is formed using a coating method when manufacturing the solar cell according to any one of the above (1) to (6). (8) The method for manufacturing a solar cell according to (7), wherein the photoelectric conversion layer is formed by a plasma CVD method while keeping the temperature of the metal substrate in a range of 200 to 400 ° C. (9) The method for producing a solar cell according to (8), wherein the photoelectric conversion layer contains Si.

In the present invention, a metal substrate is used. With a metal substrate, it is possible to increase the substrate temperature when forming a photoelectric conversion layer as compared with an organic flexible substrate. In addition, the above-mentioned “warpage” occurring in the organic flexible substrate,
"Wrinkles", "beko", "sag" can be prevented.
Further, when the photoelectric conversion layer is formed by a plasma CVD method using a mask, only the patterning portion does not swell in a drum shape.

However, when a metal substrate is used, it is necessary to provide an insulating layer between the metal substrate and the lower electrode. Since the resin layer is easy to form and has good insulating properties, it is preferably used as the insulating layer as described above. However, the insulating layer was formed from resin, and the substrate temperature was increased to form the photoelectric conversion layer. In this case, as described above, cracks, pinholes, peeling, and the like are likely to occur in the insulating layer.

The present inventors have found that such a problem that occurs in the insulating layer made of resin is caused by a difference in the thermal expansion coefficient between the metal substrate and the insulating layer. Specifically, during the formation of the photoelectric conversion layer, the coefficient of thermal expansion between the metal substrate and the insulating layer,
It is considered that the heat shrinkage and the internal stress are different from each other.

Therefore, in the present invention, an insulating layer made of a heat-resistant resin having the above-mentioned glass transition point and having the above-mentioned coefficient of thermal expansion is provided between the metal substrate and the lower electrode. Accordingly, when the photoelectric conversion layer is formed at a substrate temperature of 200 ° C. or higher, cracks and pinholes do not occur in the insulating layer and the insulating layer does not peel from the substrate. Therefore, a highly reliable solar cell can be obtained.
In the present invention, since the substrate temperature can be increased when the photoelectric conversion layer is formed by the plasma CVD method, the film formation rate of the photoelectric conversion layer can be increased, and the characteristics of the photoelectric conversion layer are improved. Therefore, the efficiency of the solar cell can be increased.

The insulating layer can be formed by a vapor deposition method or the like, but is preferably formed by coating because it can be mass-produced at low cost. In addition, when an insulating layer is formed by an evaporation method, a pinhole or the like is easily formed and reliability is reduced. However, when an application method is used, a pinhole does not occur, so that high reliability is realized.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a partial sectional view showing an example of the structure of a solar cell according to the present invention. The solar cell shown in FIG. 1 has an insulating layer 3, a lower electrode 4, a photoelectric conversion layer 5, and a transparent electrode 6 in this order on a metal substrate 2.

The illustrated solar cell has a configuration in which a plurality of solar cells each having a light receiving surface are connected in series.
A collecting / wiring electrode 11 is provided on the transparent electrode 6 of each cell. The illustrated collecting / wiring electrode 11 is a connecting portion between the collecting electrode and the wiring electrode. The collecting electrode is an electrode for collecting the electric power generated in each cell from the surface of the transparent electrode 6 having a relatively high specific resistance. The wiring electrode is an electrode for connecting the collection electrode of each cell to the lower electrode of an adjacent cell. In the illustrated example, the collecting / wiring electrode 11
, A connection conductor 12 extends through the transparent electrode 6 and the photoelectric conversion layer 5 and is connected to the lower electrode 4 of an adjacent cell, whereby the adjacent cells are connected in series. An interlayer insulating layer 9 exists between the transparent electrode 6 and the collecting / wiring electrode 11, and the transparent electrode 6 is provided on the interlayer insulating layer 9.
The separator insulating layer 10 exists between the two. In the illustrated example, the separator portion 101 of the separator insulating layer 10 extends through the transparent electrode 6, the photoelectric conversion layer 5, and the lower electrode 4, and insulates the lower electrodes of adjacent cells. The separator part 101 is a wall-shaped body that also extends in the depth direction in the figure.

Although not shown, plus and minus extraction electrodes are provided at both ends of the series connection.

Although not shown, it is preferable to provide a sealing member on at least the surface on the transparent electrode 6 forming side of the solar cell shown in order to suppress mechanical damage, oxidation, corrosion and the like of the solar cell. Further, such a sealing member is preferably provided also on the back surface side of the substrate 2.

Hereinafter, the configuration of each unit will be described in detail. Metal substrate The constituent material of the metal substrate 2 is not particularly limited.
Al or Ni, or an alloy containing at least two of these, stainless steel (for example, SUS301, SUS304, SUS430 specified in JIS), Fe-
Ni alloy, Fe-Ni-Cr alloy, or the like can be used. Of these, SUS304 or SUS4
Preferably, 30 is used. Although the thickness of the metal substrate is not particularly limited, it is usually about 20 to 150 μm.

Insulating Layer The insulating layer 3 is made of a heat-resistant resin. This heat-resistant resin has a glass transition point (Tg) of 260 ° C. or higher, preferably 300 ° C. or higher, more preferably 400 ° C. or higher.
When the glass transition point is low, the substrate temperature cannot be sufficiently increased when forming the photoelectric conversion layer by the plasma CVD method. That is, when the substrate temperature is increased, cracks and pinholes are generated in the insulating layer, the insulating layer is separated from the substrate, and a short circuit easily occurs between the metal substrate and the lower electrode. The higher the glass transition point of the heat-resistant resin is, the more preferable it is, but usually the upper limit is about 400 ° C. The thermal decomposition temperature of the heat-resistant resin is preferably 400 ° C. or higher, more preferably 500 ° C. or higher.

The thermal expansion coefficient of the heat-resistant resin constituting the insulating layer is 0.1 to 5 times the thermal expansion coefficient of the metal substrate. This ratio is a value calculated from the coefficient of thermal expansion at 30 to 250 ° C. If the difference in thermal expansion coefficient between the heat-resistant resin and the substrate is large, cracks and pinholes in the insulating layer and peeling of the insulating layer easily occur during the formation of the photoelectric conversion layer. Specifically, the thermal expansion coefficient of the heat-resistant resin (30 to
Value at 250 ° C.) is preferably 1 × 10 ⁻⁶ to 50
× 10 ⁻⁶ / ° C., more preferably 5 × 10 ⁻⁶ to 50
× 10 ^-6 / ° C. On the other hand, the thermal expansion coefficient (3
0 to 250 ° C.) is usually 5 × 10 ^{−6 to} 25
× 10 ⁻⁶ / ° C., for example, stainless steel (SU
In S), about 10 × 10 ^-6 to 18 × 10 ^-6 / ° C.
It is about 0 × 10 ^{−6 to} 11 × 10 ⁻⁶ / ° C.

The volume resistance of the heat-resistant resin is preferably 100 kΩ · cm or more, particularly preferably 1 MΩ · cm or more in order to secure sufficient insulation. The heat-resistant resin, the tensile strength of 10 to 30 kg / mm ^2, elongation of 5 to 80% tensile modulus 300~1200kg / mm ^2, water absorption (24 h immersion, 23 ° C.) 0-5 %.

Examples of the heat-resistant resin preferably used in the present invention include polyimide, polybenzimidazole, polyamideimide and the like. In particular, a polyimide represented by the following formula (1) is preferable.

[0028]

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The polyimide represented by the above formula (1) has a coefficient of thermal expansion (value at 30 to 250 ° C.) of 1 × 10 ⁻⁶ or ^less .
About 50 × 10 ⁻⁶ / ° C., usually 5 × 10 ⁻⁶ to 50 × 10
⁻⁶ / ° C., the difference from the coefficient of thermal expansion of the metal substrate is small, and the volume resistance is 10 ¹⁶ Ω · cm or more, usually 10 ¹⁷ to 10
It has excellent insulation properties of ¹⁸ Ω · cm or more, and also has excellent coating properties. The tensile strength is 10-30kg
/ mm ² , elongation about 5 to 80%, tensile modulus 3
Since the mechanical properties are excellent at about 1200 to 1200 kg / mm ² , a tough coating film can be obtained. The water absorption (immersion for 24 hours, 23 ° C.) is about 0 to 5%, and the dielectric breakdown strength is 6 to 8 kV.
/ Mil, and the surface resistance is about 10 ¹⁶ Ω or more. Moreover, when it is used as a coating film, the adhesion to a metal substrate is high.

The polyimide represented by the above formula (1)
No generation of organic gases was observed up to about 00 ° C.
Even when heated, the weight loss is less than 1% by weight.

The insulating layer made of polyimide represented by the above formula (1) is coated with a polyimide coating agent commercially available as Unitimide U-imide type A, type B, type C, etc., and then heat-treated. It can be formed by curing (imidization).

In addition, as polybenzimidazole, for example, “Cerazole R” manufactured by Hoechst Celanese
As polyamideimide, for example, “TI-50” manufactured by Toray Industries, Inc.
"00" is preferably used as the liquid crystal polyester, for example, Sumitomo Chemical "Econol".

The thickness of the insulating layer is preferably from 0.1 to 20.
μm, more preferably 1 to 10 μm. If the insulating layer is too thin, pinholes are likely to occur in the insulating layer. on the other hand,
If the insulating layer is too thick, the insulating layer becomes brittle or cracks easily occur.

The insulating layer is preferably formed by a coating method. The application means is not particularly limited, and for example, any of roll coating, spin coating, dipping, spraying and the like may be used. After formation of the coating film, curing and drying are performed as necessary to form an insulating layer. For example, the polyimide represented by the above formula (1) is obtained by thermosetting after application.

The solvent used for preparing the coating liquid is not particularly limited as long as the resin and the monomer component and the oligomer component of the raw material are soluble. For example, when forming an insulating layer made of polyimide represented by the above formula (1), the solvent may be dimethylacetamide, dimethylformamide,
N-methylpyrrolidone or the like may be used. The concentration of the raw material in the solution is not particularly limited, but is preferably 10 to 5%.
0% by weight, more preferably 25 to 45% by weight. The viscosity of the coating solution is not particularly limited, but the viscosity at 20 ° C. is preferably 1 to 100 poise, more preferably 1 to 100 poise.
50poise.

The number of revolutions when spin coating is used for coating is preferably 50 to 3000 rpm, more preferably 100 to 2500 rpm. The coating film is dried by controlling the number of rotations as necessary. After application, 200 ° C
The following drying step may be included.

Lower Electrode The lower electrode 4 is made of metal. The material for the lower electrode is not particularly limited. For example, Al or stainless steel may be used, but Al is preferably used. Since Al has a low specific resistance, deterioration due to energy loss and heat generation is small. By the way, in the solar cell, the light reflected by the lower electrode through the photoelectric conversion layer enters the photoelectric conversion layer again, and this reflected light is also converted into electric energy. Therefore, it is preferable that the lower electrode has a high reflectance, but Al having a high light reflectance is also excellent in this respect. Further, Al has high thermal conductivity, good corrosion resistance, and is inexpensive.

The thickness of the lower electrode is not particularly limited, but is preferably 0.01 to 10 μm. The lower electrode is preferably formed by a vapor deposition method such as a sputtering method.

A diffusion preventing layer is provided between the lower electrode 4 and the photoelectric conversion layer 5 to prevent the constituent components of the lower electrode from diffusing into the photoelectric conversion layer. It is preferable to provide a diffusion prevention layer made of a metal such as Ti or Cr. The thickness of the diffusion preventing layer is preferably 3 to 5 nm. The diffusion preventing layer may be usually formed by a vapor deposition method such as a sputtering method.

Photoelectric Conversion Layer The photoelectric conversion layer 5 is preferably made of single crystal silicon, microcrystalline silicon or amorphous silicon having a pn junction or a pin junction, preferably a pin junction. A pn junction or a pin junction can be formed by adding a predetermined impurity when forming the photoelectric conversion layer.

Hereinafter, as a preferred combination example, an n-type semiconductor layer composed of microcrystalline silicon, a photovoltaic layer (i-layer) composed of amorphous silicon, and a p-type semiconductor layer composed of microcrystalline silicon are laminated. The photoelectric conversion layer described above will be described.

B is preferably an impurity for forming a p-type semiconductor layer.
Preferably, its content is 10¹⁷-10 ²⁰atoms / cm^ThreeIs
Is preferred. Impurity content too low or too high
Also, the energy conversion efficiency is reduced.

P is preferably an impurity for forming an n-type semiconductor layer.
Preferably, its content is 10¹⁷-10 ²⁰atoms / cm^ThreeIs
Is preferred. Impurity content too low or too high
Also, the energy conversion efficiency is reduced.

The thickness of each layer is not particularly limited, but is preferably 5 to 40 nm for a p-type semiconductor layer, preferably 100 to 20 μm for an i-layer, and preferably 5 to 40 nm for an n-type semiconductor layer.

Usually, such a photoelectric conversion layer is preferably formed by a plasma CVD method. Plasma CV
The plasma in the method D may be either DC or AC, but AC plasma is preferably used. The AC plasma can be used at a frequency of several hertz to several gigahertz.

The p-type semiconductor layer is made of SiH ₄ , H ₂ , B
_{Using 2} H ₆ or the like, the flow rate ratio B ₂ H ₆ / SiH ₄ is determined according to the target impurity content, and the substrate temperature is changed from room temperature to 450 ° C.
C., preferably 200-400.degree. C., more preferably 20.degree.
It may be formed at 0 to 300 ° C., at an operating pressure of 0.01 to 10 Torr, and at an input power of 10 to 2000 W (frequency 10 ⁶ to 10 ⁹ Hz).

The i-layer is formed by using SiH ₄ , H ₂ or the like as a raw material, at a flow rate of 1 to 2000 sccm, and at a substrate temperature of room temperature to 45 ° C.
0 ° C, preferably 200-400 ° C, more preferably 2 ° C
What is necessary is just to form it at 60-380 degreeC, operating pressure 0.01-10 Torr, and input electric power 10-2000W.

The n-type semiconductor layer is made of SiH ₄ , H ₂ , P
Using H ₃ or the like, the flow rate ratio PH ₃ / SiH ₄ is determined according to the target impurity content, and the substrate temperature is changed from room temperature to 450 ° C.
Preferably from 200 to 400C, more preferably from 250 to
What is necessary is just to form it at 350 degreeC, operating pressure 0.01-10 Torr, and input electric power 10-2000W.

The constituent material of the transparent electrode transparent electrode 6 is not particularly limited, transparency,
Good conductivity, tin oxide, ITO
(Indium tin oxide) and ZnO are preferred. The thickness of the transparent electrode is not particularly limited, but is usually preferably 10 to 100 nm. The transparent electrode made of the above material is usually formed by a vapor phase growth method such as a sputtering method.

Interlayer insulating layer, separator insulating layer Interlayer insulating layer 9 and separator insulating layer 1 in the illustrated example
The material constituting 0 is not particularly limited as long as it has an insulating property and can form the structure shown in the figure, but it is usually preferable to use an insulating resin. As the insulating resin, for example, a urethane resin, a phenoxy resin, or the like is preferable. The interlayer insulating layer 9 and the separator insulating layer 10
May be composed of the same material or different materials.

The thickness of the interlayer insulating layer 9 is preferably 5 to 40 μm, and the thickness of the flat portion of the separator insulating layer 10 is preferably 5 to 10 μm.

The interlayer insulating layer and the separator insulating layer may be usually formed by a coating method such as screen printing.
Interlayer insulating layer 9 and separator insulating layer 1 in the illustrated example
0 is usually formed by the following procedure. First, after forming the photoelectric conversion layer 5, the interlayer insulating layer 9 is formed in a predetermined pattern by screen printing or the like. Next, the interlayer insulating layer 9
After the transparent electrode 6 is formed thereon, a groove penetrating the transparent electrode 6, the interlayer insulating layer 9, the photoelectric conversion layer 5, and the lower electrode 4 is formed by, for example, laser processing. The laminated body from the lower electrode 4 to the transparent electrode 6 is divided by the groove and separated into cells. Next, the separator insulating layer 1 is formed on the transparent electrode 6.
0 is formed in a predetermined pattern by screen printing or the like. At this time, the insulating material penetrates into the groove, and the separator part 101 is formed.

The interlayer insulating layer 9 is provided to prevent a short circuit between the transparent electrode 6 and the lower electrode 4 at the time of forming the separator portion 101. In addition, the interlayer insulating layer 9 also has a function of improving the breakdown voltage of the solar cell. For example, if a minute defect or inhomogeneity exists in the photoelectric conversion layer 5, the lower electrode 4 is located at that position.
Although a short circuit may occur between the first electrode and the transparent electrode 6, the provision of the interlayer insulating layer 9 forms a capacitor having a relatively high capacitance, so that occurrence of such dielectric breakdown can be prevented.

The constituent materials of the collecting / wiring electrode and the connecting conductor collecting / wiring electrode 11 are not particularly limited.
Usually, it is preferable to use Ag. The thickness of the collecting / wiring electrode is preferably 5 to 10 μm.

The collecting / wiring electrodes may be usually formed by a coating method such as screen printing. In the illustrated example, the collecting / wiring electrode 11 is usually formed in the following procedure. First, after forming the separator insulating layer 10, the collecting / wiring electrode 11 is formed in a predetermined pattern by screen printing or the like. Next, in a region where the interlayer insulating layer 9 does not exist, the collecting / wiring electrode 11 is pierced by, for example, laser processing, and the lower electrode 4 penetrates the transparent electrode 6 and the photoelectric conversion layer 5.
To form holes. At the time of this perforation, the constituent material of the collecting / wiring electrode 11 is melted and penetrates into the hole, and the connection conductor 12 is formed.

[0056] The sealing member mechanical damage, oxide, as the sealing member for suppressing corrosion, the resin film is preferable. The resin film may be formed by coating or sticking. The sealing member is preferably provided at least on the surface on the transparent electrode 6 side, more preferably on the back surface side of the substrate 2.

Hereinafter, an example of a method for forming a resin film by sticking will be described. In this example, a sealing member in which a buffer adhesive layer containing a thermosetting resin is provided on at least one surface of a resin base material having a light transmitting property and a heat resistance property is used.

The glass substrate has a glass transition point Tg of 65 ° C.
Or the heat-resistant temperature (or continuous use temperature) is 80
C. or higher, or a resin film that satisfies both of these conditions and has translucency. Such a resin film does not deteriorate in performance even when it is directly exposed to a light source such as sunlight and heated.

As a substrate made of a resin having a glass transition point Tg of 65 ° C. or more and / or a heat-resistant temperature of 80 ° C. or more, a polyethylene terephthalate film (Tg6
9 ° C), polyethylene naphthalate heat-resistant film (Tg
113 ° C.); ethylene trifluorochloride resin [PCTFE:
NEOFLON CTFE (manufactured by Daikin Industries, Ltd.)] (heat-resistant temperature 150 ° C.), polyvinylidene fluoride [PVDF:
Denka DX film (manufactured by Denki Kagaku Kogyo Co., Ltd.)] (heat-resistant temperature 150 ° C .: Tg 50 ° C.), polyvinyl fluoride [P
VF: Tedlar PVF film (manufactured by DuPont)] (heat-resistant temperature: 100 ° C.) or a fluoride homopolymer or ethylene tetrafluoride-perfluorovinyl ether copolymer [P
FA: Neoflon: PFA film (manufactured by Daikin Industries, Ltd.)] (heat resistant temperature: 260 ° C.), ethylene tetrafluoride-hexafluoropropylene copolymer [FEP: Toyofuron film FEP type (manufactured by Toray Industries, Inc.)] ° C), tetrafluoroethylene-ethylene copolymer [ETFE: Tefzel ETFE film (manufactured by DuPont) (heat resistant temperature 150
° C), AFLEX film (manufactured by Asahi Glass Co., Ltd .: Tg83)
℃)] or other fluorine-based film; aromatic dicarboxylic acid-bisphenol copolymerized aromatic polyester [PAR: casting (ELMEC manufactured by Kaneka Chemical Co., Ltd.)] (heat-resistant temperature: 290 ° C .: Tg 215 ° C.) Acrylate film; polysulfone [PSF:
Sumilite FS-1200 (Sumitomo Bakelite)
(Tg 190 ° C.), polyether sulfone [PES: Sumilite FS-1300 (Sumitomo Bakelite)] (Tg
Polycarbonate film [PC: Panlite (manufactured by Teijin Chemicals Ltd.)]
(Tg 150 ° C); functional norbornene resin [ARTON (manufactured by JSR)] (heat-resistant temperature 164 ° C:
Tg 171 ° C.); polymethyl methacrylate (PMM
A) (Tg 93 ° C); olefin-maleimide copolymer [TI-160 (manufactured by Tosoh Corporation)] (Tg 150 ° C or more), para-aramid [Aramica R: manufactured by Asahi Kasei Corporation] (heat-resistant temperature 200 ° C), fluorinated polyimide (heat-resistant) Temperature 200 ° C
Above), polystyrene (Tg 90 ° C), polyvinyl chloride (Tg 70-80 ° C), cellulose triacetate (Tg
g 107 ° C).

Among these, the polyethylene naphthalate heat-resistant film (Tg 113 ° C.) has a higher heat resistance (Tg), heat resistance during long-term use, Young's modulus (stiffness), breaking strength, and heat shrinkage rate than the polyethylene terephthalate film. , Low oligomers, excellent gas barrier properties, hydrolysis resistance, water vapor transmission rate, thermal expansion coefficient, physical property deterioration due to light, etc., and breaking strength compared to other polymers , Heat resistance, dimensional stability, moisture permeability,
Because it is excellent in terms of total balance such as cost,
preferable.

The glass transition point Tg of the resin substrate is preferably at least 65 ° C., more preferably at least 70 ° C., further preferably at least 80 ° C., particularly preferably at least 110 ° C. Although the upper limit of Tg is not particularly limited, it is usually 130 ° C.
It is about. Further, the heat resistant temperature or the continuous use temperature is preferably 80 ° C. or more, more preferably 100 ° C. or more, and further preferably 110 ° C. or more. The higher the heat resistance temperature or the continuous use temperature, the better, and the upper limit is not particularly limited, but is usually about 250 ° C.

The thickness of the resin substrate may be appropriately determined according to the structure of the solar cell, the strength and the bending rigidity required for the resin substrate, etc., and is usually 5 to 100 μm.

The transmissivity of the resin substrate is preferably such that 70% or more, particularly 80% or more of the light in the visible light region is transmitted.

The buffer adhesive layer preferably contains a thermosetting resin component and an organic peroxide before thermocompression bonding.

As the thermosetting resin component, ethylene-vinyl acetate copolymer [EVA (vinyl acetate content of 15 to
About 50%)].

Examples of the organic peroxide include 2,5-dimethylhexane-2,5-dihydroperoxide;
2,5-dimethyl-2,5-di (t-butylperoxy) hexane-3; di-t-butyl peroxide;
2,5-dimethyl-2,5-di (t-butylperoxy) hexane; dicumyl peroxide; α, α′-bis (t-butylperoxyisopropyl) benzene; n
-Butyl-4,4-bis (t-butylperoxy) valerate; 2,2-bis (t-butylperoxy) butane; 1,1-bis (t-butylperoxy) -3,3
5-trimethylcyclohexane; t-butylperoxybenzate; benzoyl peroxide can be used. These may be used alone or in combination of two or more, and the combination ratio when using in combination is arbitrary. The amount of the organic peroxide to be used per 100 parts by weight of the thermosetting resin component is preferably 10 parts by weight or less, more preferably 0.5 to 6 parts by weight.

The thickness of the buffer adhesive layer may be appropriately determined according to the structure of the solar cell, the use environment, and the like, but is preferably 3 to 500 μm, more preferably 3 to 50 μm, and still more preferably 10 to 40 μm. . If the buffer adhesive layer is too thin, the buffer effect will be insufficient. On the other hand, when the buffer adhesive layer is too thick, the light transmittance is reduced, and burrs are easily generated at the time of punching or the like. However, since the buffer adhesive layer has much better light transmittance than the resin base material, when used under high illuminance such as outdoors, there may be no problem even if the thickness is increased to about 10 mm.

As means for providing the buffer adhesive layer on the resin substrate, known means such as coating or extrusion coating can be used.

The buffer adhesive layer may be embossed. When laminating the sealing member to the solar cell,
If embossing is performed so that a passage for bubbles is formed, mixing of bubbles is reduced.

Next, an example of a method for forming a resin film by coating will be described. The resin film formed by the coating method is slightly inferior in terms of flatness, weather resistance, etc., compared to the resin film formed by sticking, but it is used when incorporated into equipment or used mainly for indoor use. Is no problem. In the coating method, the laminating step and the subsequent flattening step required in the above-mentioned attaching method can be omitted, so that the manufacturing cost can be reduced.

The resin used in this case has excellent transparency,
It is preferable that there is little discoloration due to aging and light deterioration, and particularly preferable is a thermosetting resin. As the thermosetting resin, for example, a fluorine resin, polyurethane, polyester, epoxy resin, and phenoxy resin can be used.

The resin coating may be formed by a screen printing method, a spin coating method, or the like.

[0073]

EXAMPLE A solar cell sample having the structure shown in FIG.
It was produced by the following procedure. First, a metal substrate 2 made of SUS430 (height 230 mm, width 360 mm, thickness 50 μm,
The coefficient of thermal expansion at 0 to 250 ° C. is about 10.5 × 10 ⁻⁶
/ ° C), a polyimide coating agent (U-imide type B manufactured by Unitika) is applied to the entire surface of one side by a roll coating method, and is kept at 170 ° C for 10 minutes, and then kept at 350 ° C for 60 minutes. Thus, the coating film was cured, and an insulating layer 3 having a thickness of 6 μm was obtained. The properties of the cured polyimide are as follows: a coefficient of thermal expansion at 30 to 250 ° C. is 45 × 10 ⁻⁶ / ° C., a glass transition point is 400 ° C. or more,
Thermal decomposition onset temperature is 560 ° C, volume resistance is 10 ¹⁸ Ω · cm,
Tensile strength 13 kg / mm ² , elongation 23%, tensile elasticity 370 kg / mm ² , water absorption (24 hours immersion, 23 ° C)
Is 2.9%, the dielectric breakdown strength is 6.9 kV / mil, and the surface resistance is 10 ¹⁶ Ω or more.

Next, a lower electrode 4 made of Al and having a thickness of 0.3 μm is formed by a sputtering method.
A diffusion preventing layer of stainless steel having a thickness of 5 nm was formed.

Next, a photoelectric conversion layer 5 was formed on the diffusion preventing layer by the following procedure. First, an n-type microcrystalline silicon layer was formed to a thickness of 20 nm by a plasma CVD method. At this time, the raw material gas and its flow rate were: PH ₃ + H ₂ mixed gas (PH ₃ / H ₂ = 0.2%): 30 sc
cm, SiH ₄ : 4 sccm, H ₂ : 750 sccm, and other conditions were as follows: substrate temperature: 300 ° C., operating pressure: 1 Torr, input power: 100 W (13.56 MHz). Subsequently, the i-type amorphous silicon layer is
It was formed to a thickness of 0 nm by a plasma CVD method. At that time, the source gas and its flow rate were SiH ₄ : 50 sccm, H ₂ : 500 sccm, and other conditions were: substrate temperature: 260 ° C., operating pressure: 1 Torr, input power: 100 W (13.56 MHz). Subsequently, a p-type microcrystalline silicon layer was formed to a thickness of 20 nm by a plasma CVD method. At this time, the raw material gas and the flow rate thereof are B ₂ H ₆ + H ₂ mixed gas (B ₂ H ₆ / H ₂ = 0.2%): 30
sccm, SiH ₄ : 5 sccm, H ₂ : 950 sccm, and other conditions were: substrate temperature: 280 ° C., operating pressure: 1 Torr, input power: 200 W (13.56 MHz).

Next, a urethane-based insulating resin composition is printed on the photoelectric conversion layer 5 in a predetermined pattern by a screen printing method using a 150-mesh polyester screen, and then left in an oven at 160 ° C. for 10 minutes. And heat-cured to form an interlayer insulating layer 9 having a thickness of 20 μm.

Next, a transparent electrode 6 having a thickness of 60 nm was formed by sputtering in an Ar atmosphere using ITO (indium tin oxide) as a target.

Next, a groove was formed by laser scribing, and a urethane insulating resin composition was screen-printed thereon, thereby forming a 10 μm thick separator insulating layer 10 having a separator portion 101.

Next, the silver paste is screen-printed and cured to form a 6 μm thick collecting / wiring electrode 11.
Was formed. Finally, a silver paste was screen-printed to form a plus-side extraction electrode and a minus-side extraction electrode, thereby obtaining a solar cell sample No. 1.

In addition, the substrate temperature at the time of forming the photovoltaic layer (i-layer) was raised by 20 ° C. to 280 ° C.
In the same manner as in No. 1, a solar cell sample No. 2 was obtained.

In sample No. 1, the photovoltaic layer (i-layer)
Although the film formation rate at the time of formation was 0.7 nm / s, the sample No. in which the substrate temperature was increased to form a photovoltaic layer (i-layer) was used.
In No. 2, it was 1.0 nm / s. In addition, for each solar cell sample, 100
As a result of irradiating mW / cm ² light and measuring the photocurrent, the sample
The photocurrent of No. 1 was 14 mA / cm ² , and the photocurrent of sample No. ^{2 in which} the substrate temperature was increased to form a photovoltaic layer (i-layer) was 1
It was 6 mA / cm ² , and it was confirmed that there were no cracks and pinholes that would cause a short circuit in both samples.

[0082]

According to the present invention, the performance is high, and
The reliability of a solar cell excellent in mass productivity can be improved, and such a solar cell can be produced at low cost.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a solar cell of the present invention.

[Explanation of symbols]

 2 Substrate 3 Insulating layer 4 Lower electrode 5 Photoelectric conversion layer 6 Transparent electrode 9 Interlayer insulating layer 10 Separator insulating layer 101 Separator part 11 Collection / wiring electrode 12 Connection conductor

Claims (9)

[Claims] 1. A lower electrode, a photoelectric conversion layer and a transparent electrode are provided in this order on a surface of a metal substrate, and an insulating layer exists between the metal substrate and the lower electrode. The heat-resistant resin has a glass transition point of 260 ° C. or higher, and the heat-resistant resin has a glass transition point of 30 to
The coefficient of thermal expansion at 250 ° C. is 30 to
A solar cell having a coefficient of thermal expansion of 0.1 to 5 times at 250 ° C. 2. The solar cell according to claim 1, wherein the heat-resistant resin has a coefficient of thermal expansion at 30 to 250 ° C. of 1 × 10 ⁻⁶ to 50 × 10 ⁻⁶ / ° C. 3. The solar cell according to claim 1, wherein said insulating layer is a coating film. 4. The solar cell according to claim 1, wherein the heat-resistant resin is a polyimide represented by the following formula (1). Embedded image 5. The solar cell according to claim 1, wherein said insulating layer has a thickness of 0.1 to 20 μm. 6. The method according to claim 6, wherein the metal substrate is made of Cu, Al and Ni.
Or a metal or alloy containing at least one of the following: stainless steel, Fe—Ni alloy and Fe—N
The solar cell according to any one of claims 1 to 5, which is one kind of an i-Cr alloy. 7. A method of manufacturing a solar cell according to claim 1, wherein the insulating layer is formed using a coating method when manufacturing the solar cell according to claim 1. 8. The temperature of the metal substrate is set to 200 to 400 ° C.
While the photoelectric conversion layer is maintained in the range of plasma CV.
The method for manufacturing a solar cell according to claim 7, wherein the solar cell is formed by a D method. 9. The method according to claim 8, wherein the photoelectric conversion layer contains Si.