JPH0888385A - Thin film solar battery - Google Patents

Abstract

PURPOSE: To improve humidity resistance and weather resistance of a thin film solar battery fixed between water proof films by laminating thin films on a plastic film substrate. CONSTITUTION: A PVDF resin film 9 of good weather resistance is laminated in a surface of an acrylic resin film 8 of good weather resistance and is used for a waterproof film 72. Ultraviolet ray absorption agent is added to the acrylic resin 8 and acrylic adhesive or hot melt adhesive of high adhesion strength which does not cause yellowing is used for adhesive of the waterproof film 72.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film solar cell using a flexible insulating substrate.

[0002]

2. Description of the Related Art Solar cells have been attracting attention as clean energy, and their technological progress has been remarkable. In particular, since a photoelectric conversion layer mainly made of amorphous silicon can be easily formed into a large area and is inexpensive, a thin-film solar cell using the photoelectric conversion layer is highly expected. Conventional solar cells use glass substrates, but they are thick and heavy, and have the drawback of being easily broken, and there is a demand for thinness and lightness for reasons such as improving workability by applying them to outdoor roofs. Is getting stronger. To meet these demands, a flexible type thin film solar cell using a flexible plastic film and a thin film metal film as a substrate is being put into practical use. Such flexible type solar cells
In order to use it for a long period of 15 years, a moisture-proof film is laminated on both front and back sides of the solar cell via adhesive layers to prevent moisture from entering. FIG. 2 shows a cross-sectional structure of such a flexible solar cell, in which a flexible plastic film substrate 1 is provided on one surface thereof with a first electrode layer 2 made of metal, and a crystalline or amorphous semiconductor having a pin junction. The layer 3 and the transparent second electrode layer 4 made of ITO or the like are laminated, and on the other surface side, for example, Japanese Patent Application No. 5-6797.
The third electrode layer 5 described in No. 6 is formed,
It is connected to the first electrode layer 2 or the second electrode layer 4 through a through hole (not shown) formed in the substrate 1. The solar cell having such a structure includes a transparent moisture-proof film 71 having a transparent adhesive layer 61 on the second electrode layer and a moisture-proof film 72 having an adhesive layer 62 on the third electrode layer 5. It is sandwiched.

[0003]

By the way, in such a conventional thin film solar cell, it is transparent due to deterioration due to oxidation or heat due to ultraviolet rays, oxygen, and intrusion of rainwater and gaseous water in the air outdoors. There is a problem that the solar cell is affected by peeling from the moisture-proof film and the adhesive layer, a decrease in adhesive strength, a discoloration of the adhesive, and the like, and the output of the solar cell decreases. Therefore, such a thin film solar cell is not yet sufficient for long-term outdoor use, and further improvement has been desired.

An object of the present invention is to solve the above-mentioned problems and to provide a thin film solar cell which is excellent in weather resistance as well as moisture-proof so as not to deteriorate the characteristics due to invasion of water.

[0005]

In order to achieve the above-mentioned object, the present invention provides a flexible substrate having at least a first electrode layer, a photoelectric conversion semiconductor layer, and a transparent second electrode layer laminated on each other to form an adhesive agent. In a thin-film solar cell sandwiched by a moisture-proof film via a layer, at least the moisture-proof film on the transparent second electrode layer forms a polyvinylidene fluoride (PVD
F) An acrylic resin film covered with resin. The acrylic resin film whose surface is covered with PVDF resin is preferably an acrylic resin film laminated with a PVDF resin film. It is effective that the acrylic resin film is made of an acrylic resin to which an ultraviolet absorber is added. The adhesive layer in contact with the acrylic resin film may be made of an acrylic adhesive or a hot-melt adhesive.

[0006]

Function: Acrylic resin and PVDF resin have been
It is known as a material exhibiting excellent weather resistance. However, it was difficult to combine both of them to form a film. The present inventor has succeeded in coating a PVDF resin film on an acrylic resin film by making full use of surface treatment technology and laminating technology.
Therefore, it goes without saying that the thin film solar cell formed by combining materials having excellent weather resistance is excellent in moisture resistance and weather resistance. Furthermore, by adding an ultraviolet absorber to the acrylic resin film, it becomes strong against ultraviolet rays.

Further, by using an acrylic adhesive having a good adhesiveness with an acrylic resin and a hot-melt adhesive as the adhesive, an adhesive layer such as conventional EVA (ethylene vinyl acetate copolymer) can be formed. This eliminates the need for problems such as yellowing and eliminates problems such as yellowing, improves workability, and reduces film thickness.

[0008]

EXAMPLE FIG. 1 shows the structure of a thin film solar cell according to an example of the present invention.
Shown in The film-shaped insulating substrate 1 is required to have heat resistance because the electrode layer and the amorphous semiconductor layer are formed at about 200 ° C. Therefore, as the plastic film having heat resistance, polyimide, polyetherimide, polysulfone, polyether sulfone, polyphenylene sulfide, para aramid, polyether ketone, or a fluorine-based film in general, but especially polyimide, para Suitable are aramid-based and fluorine-based films in general. However, a foil of stainless steel, nickel, copper or the like may be used as the thin film metal film, and a heat resistant insulating film may be applied to the surface. Alternatively, it can be used as it is as a conductive substrate which also serves as the first electrode layer. The thin film semiconductor layer 3 is a thin film mainly composed of amorphous silicon having a pin junction which is generally formed. As the electrode layers 2, 4, and 5, a metal film, a transparent conductive film, and a metal film are formed by a method such as sputtering.

As the moisture-proof film 71 on the light incident side, a transparent plastic film having a low moisture permeability is used. According to the present invention, the surface of the acrylic resin (polymethylmethacrylate) film 8 is covered with a fluorine-based PVDF resin. The broken film is used. Acrylic resin 8
A benzophenone type, a benzotriazole type, an acrylate type, a salicylate type, or the like is added as an ultraviolet absorber.

The moisture-proof film 72 on the side opposite to the light incident side is
It does not necessarily have to be transparent. For example, in addition to the above film, a metal foil such as aluminum is sandwiched with a plastic film, and even if the plastic film itself has a slightly high water permeability, the metal foil sandwiched with the plastic film It is possible to use a device that blocks invading water. Adhesive layer 6
Acrylic resins or hot melt adhesives are used for 1 and 62.

Example 1: A polyimide film (manufactured by Toray DuPont, trade name: Kapton) as the film substrate 1.
The first electrode layer 2 is an Ag film, the thin film semiconductor layer 3 is an amorphous silicon film having a nip junction, the second electrode layer 4 is an ITO film, and the third electrode layer 5 is A on the back side of the insulating substrate 1.
Each g film was formed by a predetermined device to obtain a solar battery cell. The moisture-proof films 71 and 72 are made of the same material, and one side of the acrylic resin film 8 containing a UV absorber having a thickness of 30 μm is corona-treated to form a PV film having a thickness of 50 μm.
While extruding the DF film 9 with an extruder, the acrylic resin film is laminated to form a transparent moisture-proof film having a thickness of 80 μm. A solution-type acrylic resin having a thickness of 30 μm is provided on the back surfaces of the moisture-proof films 71 and 72.
And the adhesive layers 61 and 62 were formed. The moisture-proof film with the adhesive was set on both sides of the film substrate 1 on which the solar cell was formed, and laminated at a temperature of 130 ° C. under vacuum heating and pressure bonding conditions for 15 minutes to prepare a thin film solar cell.

Example 2: Thickness of a white film (DuPont, trade name: Tedra-PVF) obtained by sandwiching the moisture-proof film 72 on the back side of the solar cell of Example 1 with an aluminum foil sandwiched with polyvinyl fluoride (PVF). A thin-film solar cell was produced in the same manner as in Example 1 except that the moisture-proof film having a thickness of 120 μm was used.

Example 3 Adhesive layers 61 and 62 were set on both sides of a solar cell with a modified polyolefin sheet hot melt adhesive, and a thin film solar cell was prepared in the same manner as in Example 1. Comparative Example Same as Example 1 except that the moisture-proof films 71 and 72 of Example 1 were polyethylene naphthalate (PEN) films and the adhesives 61 and 62 were changed to EVA (ethylene vinyl acetate copolymer) having a thickness of 400 μm. Then, a thin film solar cell was produced.

In each of the above Examples 1 to 3 and Comparative Example, a lead wire is drawn out from the electrode of the solar cell to the outside so that the characteristics can be evaluated. The thin-film solar cells of Examples 1 to 3 and Comparative Example above were subjected to a 1000-hour weather meter test (corresponding to about 5 years of outdoor exposure) as an accelerated outdoor exposure test. No change was observed, and the surface of the comparative example was slightly yellow. Also,
As a result of measuring the conversion efficiency as the output characteristic of the solar cell, in Examples 1 to 3, the same value as the initial value was shown, but in Comparative Example
It was down by 1.0%.

As described above, it is understood that the thin film solar cells of the examples of the present invention are superior in moisture resistance and weather resistance to the comparative examples in terms of appearance and characteristics. In the above examples, the thin film solar cell in which the third electrode layer is formed on the substrate surface is used, but the thin film solar cell configured only on the one surface of the substrate, that is, the thin film solar cell without the third electrode layer. It is clear that it is effective when applied to.

[0016]

EFFECTS OF THE INVENTION According to the present invention, a moisture-proof film in which a PVDF resin is coated on an acrylic resin film is used, and further, an acrylic resin and a hot melt system are used as an adhesive, and an ultraviolet ray absorbing film is used in the acrylic resin film. By adding the agent, it was possible to obtain a thin film solar cell having excellent moisture resistance and weather resistance.

Also, an adhesive layer such as conventional EVA (ethylene vinyl acetate copolymer) is not required, no problems such as yellowing occur, workability can be improved, and film thickness can be reduced.
It is effective in reducing the cost of thin-film solar cells.

[Brief description of drawings]

FIG. 1 is a sectional view showing the structure of a thin film solar cell according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing an example of the structure of a conventional thin film solar cell.

[Explanation of symbols]

 1 film-like insulating substrate 2 first electrode layer 3 thin film semiconductor layer 4 transparent second electrode layer 61, 62 adhesive layer 71 transparent moisture-proof film 72 moisture-proof film

Claims (5)

[Claims] 1. At least a first electrode layer on a flexible substrate,
A photoelectric conversion semiconductor layer and a transparent second electrode layer are laminated and sandwiched by a moisture-proof film via an adhesive layer, and at least the moisture-proof film on the transparent second electrode layer has a surface of polyvinylidene fluoride (PVDF). ) A thin-film solar cell, which is an acrylic resin film covered with a resin. 2. The thin film solar cell according to claim 1, wherein the acrylic resin film whose surface is covered with PVDF resin is an acrylic resin film laminated with a PVDF resin film. 3. The thin film solar cell according to claim 1, wherein the acrylic resin film is made of an acrylic resin containing an ultraviolet absorber. 4. The thin film solar cell according to claim 1, wherein the adhesive layer in contact with the acrylic resin film is made of an acrylic adhesive. 5. The thin-film solar cell according to claim 1, wherein the adhesive layer in contact with the acrylic resin film comprises a hot melt adhesive.