JPH06140651A - Solar cell module - Google Patents

Abstract

PURPOSE:To provide a solar cell module which is stable against an outdoor environment and a thermal stress given by a temperature cycle test, etc., has a bending strength and has a large power-generating region. CONSTITUTION:At least a semiconductor layer 101 which is a photoelectric conversion layer, a transparent conductive layer 101 and a collector electrode 101 are formed on a conductive substrate 100 to form a photosensor 106. A solar cell module is composed of a plurality of the photosensor 106 connected to each other. The photosensors 106 are connected to each other in series with conductive adhesive 103 whose glass transition temperature is not higher than -5 deg.C.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell module, and more particularly to a solar cell module in which a plurality of photovoltaic elements formed on a conductive substrate are arranged in series.
In particular, it relates to a serialized solar cell module.

[0002]

2. Description of the Related Art Recently, it is predicted that the greenhouse effect due to an increase in CO ₂ will cause global warming, and the demand for clean energy is increasing more and more. Further, nuclear power generation that does not emit CO ₂ has not solved the problem of radioactive waste treatment, and safer and cleaner energy is desired.

Among the clean energies expected in the future, solar cells are especially expected to be clean, safe and easy to handle. Among various solar cells, silicon semiconductors such as amorphous silicon and polycrystalline silicon and compound semiconductors such as copper indium selenide are expected to be able to be manufactured in a large area with a thin film, and the manufacturing cost is expected to be low. Has been done.

Further, among the thin film solar cells, a conductive base material such as stainless steel may be used as the base material because it has excellent weather resistance, impact resistance and flexibility. When the photovoltaic elements formed on the conductive substrate are connected in series and parallel, conventionally, a good conductor wiring material was connected by spot welding or solder as shown in FIG. The area has increased, which has been a factor of reducing the output per unit area of the solar cell module. Figure 6 (a)
[FIG. 4] is a plan view of a plurality of photovoltaic elements connected in series with a wiring material having a good conductor and before surface coating. Figure 6
(B), (c) and (d) are A of FIG. 6 (a), respectively.
It is a schematic sectional drawing at the time of cutting in -A ', BB', and CC '. In FIG. 6, 600 is a stainless steel substrate which is a conductive substrate that also serves as a lower electrode, 601 is a semiconductor layer and a transparent conductive layer, 602 is a peripheral portion of a photovoltaic element in which the transparent conductive layer is removed by etching, and 603 is a collector electrode. , 604 is a bus bar, 605 is an insulating material for insulating the transparent conductive layer from the bus bar, 606 is a wiring material of a good conductor, 607 is solder, 608 is a photovoltaic element portion, 609 is a welding of the bus bar and the conductive substrate. It is a department.

The solar cell module shown in FIG. 6 is manufactured, for example, as follows. First, a semiconductor layer as a photoelectric conversion member and a transparent conductive layer 601 are sequentially formed on a conductive substrate 600, and then the transparent conductive layer is removed by etching into a desired pattern to separate elements into a plurality of power generation regions. Subsequently, a collector electrode 603 is formed, a part of the etched portion 602 of the transparent conductive layer is cut, the element end portion of the portion where the bus bar is pulled out is insulated with an insulating material 605, and the bus bar 604 is connected. , Manufacture a photovoltaic element. Next, after connecting the wiring material 606 of a good conductor to the non-power generation region of the plurality of photovoltaic elements by a method such as welding, the bus bar of the adjacent photovoltaic element and the wiring material of a good conductor are connected by the solder 607 or the like. Then, a serialized solar cell module is manufactured.

[0006] In the method of connecting by welding, it is necessary to make a welded portion at a non-power generation portion where the power generation portion of the photovoltaic element is separated from the element. On the other hand, in order to reduce the non-power generation area such as the connection wiring area, a method of directly connecting with a conductive adhesive or solder has been proposed. Since it is weak and weak against bending, it is the current situation that it cannot stably exhibit the performance as a solar cell in an outdoor environment for a long time.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned conventional drawbacks and to provide a solar cell module which is stable against thermal stress due to a temperature cycle test and which is resistant to bending.

[0008]

In the solar cell module of the present invention, a plurality of photovoltaic elements in which at least a semiconductor layer as a photoelectric conversion layer, a transparent conductive layer and a collector electrode are formed on a conductive substrate are connected. In the solar cell module configured as described above, the photovoltaic elements are connected in series and in parallel using a conductive adhesive having a glass transition temperature of −5 ° C. or lower.

[0009]

The present inventor has conducted extensive studies on the connection method using the conductive adhesive, and as a result, the deterioration of the performance of the solar cell module due to thermal stress such as temperature cycle is caused by the contact resistance due to cracks generated at the connection portion of the conductive adhesive. It was found that the decrease in the output of the solar cell due to the action of external force such as the bending test is caused by the peeling between the conductive substrate and the conductive adhesive. The present inventor has further studied based on these findings, and by using a conductive adhesive having a glass transition temperature of −5 ° C. or less, cracks do not occur even in a temperature cycle, and moreover, bending does not occur. It has been found that it becomes possible to perform adhesion with extremely high adhesiveness, which does not cause strong peeling even with respect to the present invention, thus completing the present invention.

That is, the solar cell module of the present invention comprises a conductive substrate, at least a semiconductor layer as a photoelectric conversion layer,
A solar cell module configured by connecting a plurality of photovoltaic elements having a transparent conductive layer and a collecting electrode,
The photovoltaic elements are connected in series and parallel using a conductive adhesive having a glass transition temperature of -5 ° C or lower. By using a conductive adhesive having a glass transition temperature of −5 ° C. or less, a solar cell module that is resistant to heat stress can be manufactured, and as a result, a solar cell module that can maintain stable performance even under long-term harsh environmental conditions. It becomes possible to provide. Further, since a solar cell having a large bending strength can be manufactured, it can be installed in a place having various curved surfaces.

FIG. 1 is an example of a schematic sectional view of a solar cell module of the present invention. In FIG. 1, 100 is a conductive substrate, 101 is a layer composed of a semiconductor layer as a photoelectric conversion layer, a transparent conductive layer, and a collector electrode, 103 is a conductive adhesive having a glass transition temperature of −5 ° C. or lower, and 104 is Surface coating layer, 1
Reference numeral 05 is a reinforcing material, and 106 is a photoelectric conversion element. A back electrode layer composed of a lower electrode, a back reflection layer, etc. may be provided between the conductive substrate 100 and the semiconductor layer.

A glass transition temperature of −5 ° C. is set on the collector electrode 103 at a location where a plurality of photovoltaic elements 106 are connected in series.
After applying the conductive adhesive 103 described below, the conductive base side of the photovoltaic element on the other side to be connected is attached, and the conductive adhesive is cured to perform series connection. (For parallelization, good conductors are adhered with the above conductive adhesive for parallelization.) The conductive adhesive having a glass transition temperature of -5 ° C or lower according to the present invention contains a conductor and a resin serving as a binder. . Examples of the conductor include fine powders of silver, gold, copper, nickel, carbon compounds and the like, fine powders of fine particles plated with various metals, and the shape thereof is spherical with a diameter of 0.1 to 10 microns. Alternatively, flakes or a mixture of spherical and flakes is preferable. The resin as a binder contained in the conductive adhesive is, for example, a thermosetting resin, a room temperature curable resin,
Two-component reactive resin, thermoplastic resin, hot melt resin, etc. are used, and more specifically, epoxy resin, polyester resin, polyurethane resin, acrylic resin, polyamide resin, phenol resin, silicone resin, various rubbers and the like can be mentioned. . In addition, the conductive adhesive includes a dispersant,
Lubricants, reinforcing agents, solvents and the like are added as appropriate. The volume resistance of the conductive adhesive is preferably 10 ⁻⁴ Ω · cm or less.

The conductive substrate 100 used in the present invention includes carbon fiber, graphite sheet, stainless steel,
Examples include aluminum, copper, titanium, iron, galvanized steel sheets, and the like. A metal layer, a metal oxide, or a composite layer of a metal layer and a metal oxide layer is used as the back electrode layer of the photovoltaic element of the present invention. As the material of the metal layer, Ti, Cr, Mo, W, Al, Ag, Ni or the like is used, and as the metal oxide layer, ZnO, TiO ₂ , SnO _{2 is used.}
Are adopted. As a method for forming the metal layer and the metal oxide layer, resistance heating vapor deposition, electron beam vapor deposition, sputtering method and the like are used.

Compound semiconductors such as amorphous silicon, crystalline silicon, and copper indium selenide (CuInSe ₂ / CdS) are suitable for the semiconductor layer 101 of the photovoltaic element of the present invention. In the case of amorphous silicon, for example, silane gas or the like is decomposed and formed by a plasma CVD method, and in the case of polycrystalline silicon, for example, it can be formed by forming a sheet of molten silicon or by heat treatment of amorphous silicon. Further, in the case of CuInSe ₂ / CdS, it can be formed by a method such as electron beam evaporation, sputtering, and electrodeposition (deposition by electrolytic decomposition of an electrolytic solution).
As the structure of the semiconductor layer, a pin junction, a pn junction, a Schottky type junction, or the like is used. The semiconductor layer has a structure sandwiched at least between a conductive substrate and a transparent conductive layer.

The transparent conductive layer of the photovoltaic element is In
₂ O ₃ , SnO ₂ , In ₂ O ₃ —SnO ₂ (ITO), Zn
O, TiO ₂ , Cd ₂ SnO ₄ , high-concentration impurity-doped crystalline semiconductor layer, etc., and should be formed by using resistance heating vapor deposition, electron beam vapor deposition, sputtering method, spray method, CVD method, impurity diffusion, etc. You can Examples of the material forming the collector electrode 103 of the photovoltaic element of the present invention include Ti, Cr, Mo, W, Al, Ag, Ni, Cu,
A conductive paste such as Sn and silver paste is used. As a method of forming the collecting electrode, sputtering using a mask pattern, resistance heating, a vapor deposition method of CVD, a method of depositing a metal layer on the entire surface and then etching and patterning it, and a direct collecting electrode pattern is formed by photo-CVD. Method, a method of forming by plating after forming a negative pattern mask of the grid electrode pattern, a method of printing by forming a conductive paste, and the like. The conductive paste is usually a fine powder of silver, gold, copper, nickel, carbon, or the like dispersed in a binder polymer. As the binder polymer, resins such as polyester, epoxy, acrylic, alkyd, polyvinyl acetate, rubber, urethane, and phenol are used. Of course, the current collecting electrode is used as a conductive adhesive 104 having a glass transition temperature of −5 ° C. or lower. They may be formed of the same material, and in this case, there is an advantage that the number of steps is reduced.

The surface protective layer 104 of the photovoltaic element of the present invention
Is a method of laminating a fluororesin film via an adhesive layer, a method of applying a coating such as a fluororesin paint, a silicone resin paint and an acrylic silicone resin paint, a method of coating a transparent inorganic oxide, or the above-mentioned paint. It is formed using a method of using the above inorganic coating in combination.

As the fluororesin film, for example, ET
FE (tetrafluoroethylene-ethylene copolymer), PCT
FE (trifluorochloroethylene resin), PFA (tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer), FEP (tetrafluoroethylene-hexafluoropropylene copolymer), PVDF (vinylidene fluoride resin), PV
F (vinyl fluoride resin) or the like is used. As the adhesive layer of the fluororesin film, an adhesive containing a transparent resin such as vinyl acetate-ethylene copolymer (EVA), PVB (polyvinyl butyral), silicon resin, epoxy resin, fluorinated polyimide resin, acrylic resin as a main component. Use agents. It is desirable that the adhesive contains a crosslinking agent and an ultraviolet absorber in order to suppress photodegradation of the adhesive. Furthermore, in order to reduce the decrease in photoelectric conversion efficiency of the solar cell module, the light transmittance of the adhesive layer is 80% in the wavelength region of 400 nm or more.
The above is preferable. Further, in order to reduce reflection of incident light, the refractive index of the adhesive layer is 1.4 to 2.0.
It is preferably in the range of.

Further, as the reinforcing member 105 of the solar cell module of the present invention, a metal plate, a glass or ceramic plate, a resin plate, etc., which are insulation-coated, may be provided on the back surface via an adhesive or the like. Further, the back surface may be coated with the surface coating material.

[0019]

EXAMPLES The present invention will be described in detail below with reference to examples. The present invention is not limited to these examples. (Example 1) A solar cell module having the structure shown in Fig. 3 was produced as follows.

Preparation of Photovoltaic Element A photovoltaic element having amorphous silicon (a-Si) as a semiconductor layer was prepared. The manufacturing procedure will be described below with reference to FIG. On the cleaned stainless steel substrate 200 having a thickness of 0.125 mm, an Al film thickness of 5000 A and a ZnO film thickness of 5000 A were sequentially formed as a back surface electrode 205 of the conductor layer by a sputtering method. Then, an n-type a-Si layer is formed from SiH ₄ , PH ₃ and H ₂ by a plasma CVD method, and S
i-type a-Si layer from iH ₄ and H ₂ , SiH ₄ and BF ₃ and H
₂ to form a p-type microcrystalline μc-Si layer, and an n-layer film thickness of
A photoelectric conversion layer 201 having a laminated structure of 0 A / i layer thickness 4000 A / p layer thickness 100 A / n layer thickness 100 A / i layer thickness 800 A / p layer thickness 100 A was formed. Next, as the transparent conductive layer 202, In ₂ O ₃ having a film thickness of 700 A was formed by vapor-depositing In in an O ₂ atmosphere by a resistance heating method.
Furthermore, In ₂ O ₃ etchant (FeCl ₃ , HCl)
A part of the In ₂ O ₃ layer was removed by screen printing of the contained paste, and the photovoltaic element was separated. Next, Dupo
nt Inc. After printing the silver-making paste # 5007 in a grid pattern by a screen printing machine, heat treatment at 125 ° C. is performed to form the collector electrode 203, and then the removed portion of the transparent conductive layer is cut to separate the elements to separate elements. The amorphous silicon photovoltaic element of was produced.

Serialization A plurality of photovoltaic elements manufactured by the above method were used and connected in the configuration of FIG. 3 so as to obtain a desired electromotive voltage, and serialized. In FIG. 3, 300 is a stainless steel substrate, 301
Is an amorphous silicon semiconductor layer, 302 is In ₂ O
₃ layers, 303 is Dupont Inc. Silver paste #
The current collecting electrode formed of 5007, 304 is A. I. TEC
HNOLOGY. INC anisotropic conductive adhesive # LZTP8
658 (glass transition temperature -55 ° C), 305 is Al / Z
A back electrode layer 307 of nO is a photovoltaic element.

At the light incident side surface end of the photovoltaic element manufactured by the above method, A. I. TECHNOLOGY. INC
Silver anisotropic conductive adhesive # LZTP8658 (glass transition temperature −55 ° C.) is applied with a dispenser, and the end portions of 13 adjacent photovoltaic elements 307 are overlapped as shown in FIG. After heating at 180 ° C. for 10 minutes with the voltage applied, it was cooled and connected in series.

Surface coating Finally, after stacking the photovoltaic elements connected in series by the above method in the order of ETFE film / EVA / photovoltaic elements connected in series / EVA / insulated zinc steel sheet from the light incident side, It was placed in a vacuum laminator, evacuated to about 1 Torr, and pressurized at atmospheric pressure, heated at 140 ° C. for 30 minutes to coat the surface, and a solar cell module was produced. However, the output terminal of the solar cell module was taken out by previously forming a hole for the output terminal in the zinc steel plate of the back material.

Evaluation test After a temperature cycle test of −40 ° C. to + 90 ° C. was performed for 50 cycles, a bending test of winding around a cylinder having a diameter of 30 cm was performed to compare the output characteristics of the solar cells before and after the test. The decrease in output after the test of the solar cell module of the present example produced by the above method was hardly observed at a few% or less.

(Embodiment 2) In the same manner as in Embodiment 1, FIG.
The solar cell module having the serialized structure shown in was produced.
In this embodiment, as shown in FIG. 4, the end faces of the photovoltaic elements connected in series are covered with an insulating material 406 for insulation treatment, and the conductive adhesive is squeezed out so that the upper and lower electrodes of the photovoltaic element are exposed. A short circuit was made to prevent a decrease in electromotive voltage during serialization.

In FIG. 4, 400 is a stainless steel substrate,
401 is an amorphous silicon semiconductor layer, 402 is In
₂ O ₃ layer, 403 is Dupont. Inc silver paste #
The current collecting electrode formed of 5007, 404 is A. I. TEC
HNOLOGY, INC silver-based conductive adhesive # LTP86
50 (glass transition temperature −55 ° C.), 405 is Al / Zn
O back electrode layer, 406 is an insulating layer (polyimide resin),
Reference numeral 407 is a photovoltaic element.

After the photovoltaic element 407 manufactured in the same manner as in Example 1 is insulated with the polyimide resin 406 at least one of the overlapping points by serialization, the A.P. I. TEC
HNOLOGY. INC conductive adhesive # LTP8650
(404) was applied, pressure-bonded at a pressure of 5 psi, heated to heat at 200 ° C. for 10 minutes, cooled, and serialized.

The surface coating was carried out in the same manner as in Example 1 to prepare a solar cell module. As a result of performing the same evaluation test as in Example 1, the output decrease after the test of the solar cell module manufactured in this example was 4% or less, and almost no deterioration was observed. (Example 3) A solar power module having a serial structure shown in FIG. 5 was produced. In this example, the same material as the material of the conductive adhesive for serial connection was used for the material of the current collecting electrode.

In FIG. 5, 500 is a stainless steel substrate,
501 is an amorphous silicon semiconductor layer, 502 is In
₂ O ₃ layer, 504 is A. I. TECHNOLOGY. IN
Current collecting electrode formed with silver-based conductive adhesive # ME8452-A (glass transition temperature -25 ° C) of C, 505 is Al / ZnO
Back electrode layer, 506 is an insulating layer (polyimide resin), 5
Reference numeral 07 is a photovoltaic element.

The photovoltaic element was manufactured as follows. In ₂ O ₃ is formed, performed in the same manner as in Example 1 until removing a portion of In ₂ O ₃ layer by screen printing etching paste containing the In ₂ O _3, and then the photovoltaic elements After separating into pieces, the pieces were cut to obtain a plurality of photovoltaic elements. Next, after insulating the end surface of the cut portion of the photovoltaic element 507 with the polyimide resin 506, A. I. TECHN
OLOGY, INC conductive adhesive # ME8452-A
(Glass transition temperature −25 ° C.) 504 is printed on the current collecting electrode pattern by screen printing, and before the conductive adhesive of the current collecting electrode pattern is cured, as shown in FIG. Were overlapped with each other, and the ends were held so as to be in close contact with each other so as not to be displaced, and cured at 150 ° C. for 20 minutes to serialize.

The surface coating was carried out in the same manner as in Example 1 to prepare a solar cell module. As a result of performing the same evaluation test as in Example 1, the output decrease of the solar cell module manufactured by the above method after the test was 5% or less, and almost no deterioration was observed. Example 4 A silver-based conductive adhesive EN-4065 (glass transition temperature −5 ° C.) manufactured by Hitachi Chemical was used as a conductive adhesive, and 1
Other than curing at 80 ° C. for 60 minutes and serializing,
A solar cell module was manufactured by the same method as in Example 2.

As a result of performing the same evaluation test as in Example 1,
The output decrease after the test of the solar cell module manufactured by the above method was 8% or less, and almost no deterioration was recognized. (Comparative Example 1) As a conductive adhesive, a silver-based conductive adhesive 959-1 (glass transition temperature +69) manufactured by Able Stick Co., Ltd.
(° C.), a solar cell module was produced by the same method as in Example 2 except that curing was performed under the conditions of 150 ° C. for 40 minutes and serialization was performed.

As a result of carrying out the same evaluation test as in Example 1,
After the test of the solar cell module produced by the above method, 65
% Or less, the output decreased significantly. As described above, as is clear from Examples 1 to 4 and Comparative Example 1, the solar cell module in which a plurality of photovoltaic elements are connected in series and parallel with the conductive adhesive having a glass transition temperature of −5 ° C. or less according to the present invention is used. It was found that the non-power generation area required for connecting the photovoltaic elements can be reduced, the manufacturing process can be simplified, and the output is stable even after the temperature cycle test and the bending test.

In the above embodiments, an amorphous silicon semiconductor layer is used as the semiconductor layer of the photovoltaic conversion layer.
Although the serialized example is shown, it goes without saying that the present invention is not limited to this.

[0035]

According to the present invention, it is possible to obtain a series-structured solar cell which is stable against changes in the outdoor temperature and has a small non-power generation region. Moreover, since the solar cell module of the present invention has a large bending strength, it can be installed on a curved surface and is easy to handle. Furthermore, by adopting the configuration of the solar cell module of the present invention, it is possible to reduce the manufacturing process and the wiring material, and it is possible to manufacture at low cost.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional configuration diagram showing a solar cell module formed by connecting a plurality of photovoltaic elements of the present invention in series.

FIG. 2 is a perspective view showing a part of a photovoltaic element that constitutes the solar cell module of FIG.

FIG. 3 is a schematic cross-sectional view showing a solar cell in which a plurality of photovoltaic elements are connected in series in Example 1.

FIG. 4 is a schematic cross-sectional view showing a solar cell in which a plurality of photovoltaic elements are connected in series in Example 2.

5 is a schematic cross-sectional view showing a solar cell in which a plurality of photovoltaic elements are connected in series in Example 3. FIG.

FIG. 6 is a schematic cross-sectional view showing a solar cell formed by serially connecting photovoltaic elements formed on a conventional conductive substrate.

[Explanation of symbols]

100, 200, 300, 400, 500, 600 conductive substrate, 101 semiconductor layer, transparent conductive layer and collector electrode, 103, 304, 404, 504 glass transition temperature-
5 ° C or less conductive adhesive, 104 surface coating layer, 105 reinforcing material, 106, 307, 407, 507, 608 photovoltaic element, 201, 301, 401, 501 semiconductor layer, 202, 302, 402, 502 transparent Conductive layer, 203, 303, 403, 504, 603 Current collecting electrode, 205, 305, 405, 505 Back electrode layer, 406, 506 Insulation coating layer on end face of photovoltaic element, 601 Semiconductor layer and transparent conductive layer, 602 Transparent conductive layer removal part 603 Current collecting electrode, 604 Bus bar, 605 Insulating material, 606 Good conductor wiring material, 607 Solder, 609 Weld part.

Claims (1)

[Claims] 1. A solar cell module comprising a plurality of photovoltaic elements, each of which has at least a semiconductor layer as a photoelectric conversion layer, a transparent conductive layer, and a collector electrode formed on a conductive substrate. A solar cell module, wherein the photovoltaic elements are connected in series and parallel using a conductive adhesive having a glass transition temperature of -5 ° C or lower.