JPH0897455A - Thin film solar cell - Google Patents

Abstract

PURPOSE: To form a uniformly rough surface having a high adhesion by inserting a light scattering polymer film between a second transparent electrode layer and a moistureproof film. CONSTITUTION: On one side of a plastic film substrate 1 a first electrode layer 2, thin film semiconductor layer 3 and second transparent electrode layer 4 are laminated. On the other side a third electrode layer 5 is formed and connected through throughholes to the layer 2 or 4. A light scattering polymer film having a rough surface is formed on the layer 4 of a solar cell and this laminate is held between a transparent moistureproof film 81 through a transparent adhesive agent layer 71 and moistureproof film 82 through an adhesive agent layer 72 formed on a third electrode layer 5. The layers 71 and 72 use nylon-12, etc. The film 6 is made by polymerizing a polymethyl methacrylate (PMMA) resin with a polymer different in refractive index and hardening so as to form a rough surface. Thus a uniformly rough surface having a high adhesion to the electrode layer or moistureproof film can be formed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention uses a flexible substrate,
The present invention relates to a thin-film solar cell in which an incident surface of light is uneven in order to make effective use of light.

[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 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. A conventional solar cell is a method in which a transparent electrode made of uneven tin oxide, indium oxide or the like is formed on a transparent glass substrate, and a crystalline type and amorphous semiconductor layer and an electrode layer are sequentially formed on the transparent electrode to reduce the surface reflectance. It has been known. On the contrary, a method is also known in which a metal electrode layer is formed on a substrate, the metal electrode layer is made uneven, and a crystalline type and amorphous semiconductor layer and an electrode layer are sequentially formed on the metal electrode layer. When such a glass substrate is used, it is thick and heavy, and has the drawback of being easily broken, and due to reasons such as improved workability when installed on an outdoor roof, etc., there is a demand for thinner and lighter products. It's 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 a flexible thin-film solar cell has an advantage in that it can be formed into a film continuously on a long substrate, and thus has excellent productivity.

[0003]

When an uneven structure is formed on the surface of an electrode layer formed on a substrate, it is necessary to maintain good adhesion between the electrode layer and the substrate. In order to form a transparent electrode made of a metal oxide on a substrate so as to have a good uneven shape on the surface, it is necessary to promote the crystal growth of the metal oxide at a film forming temperature of 200 ° C. or higher. In order to withstand such a substrate temperature in a flexible substrate using an organic material, the material suitable for the substrate is extremely limited. Further, in order to form a good uneven shape on the surface, the thickness of the transparent electrode needs to be several hundreds nm or more, for example, 700 nm or more when the SnO ₂ layer is formed on the glass substrate. However, in the case of a flexible substrate, when such a thick transparent conductive film is formed, there arises a problem that the transparent conductive film itself is peeled off due to a difference in expansion coefficient from the substrate. Furthermore, as the thickness of the metal oxide layer increases, it becomes difficult to electrically separate the metal oxide layer. The same problem exists when the uneven shape is formed on the metal thin film. On the other hand, if a large amount of fine particles are mixed in the polymer material that constitutes the substrate rather than the electrode layer to form such a concavo-convex shape on the substrate surface, the physical properties of the substrate will change. For this reason, cracking of the substrate occurs and a good flexible substrate cannot be produced.

An object of the present invention is to solve the above-mentioned problems, and to form an optically excellent uneven shape on the surface of a transparent electrode layer formed with good adhesion on the surface of an insulating substrate such as a flexible substrate. To provide a thin-film solar cell having an improved photoelectric conversion rate.

[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 the thin-film solar cell sandwiched by the moisture-proof film via the layers, it is assumed that the light-scattering polymer film is inserted between the transparent second electrode layer and the moisture-proof film. The light-scattering polymer film is preferably in contact with the transparent second electrode layer or the moisture-proof film. Also, the light-scattering polymer film has two layers,
It is also possible that one layer is in contact with the transparent second electrode layer and the other one layer is in contact with the moisture-proof film.

[0006]

[Function] By inserting a light-scattering polymer film having a concavo-convex shape of 0.1 to several μm between the transparent second electrode layer on the light-incident side and the back surface of the transparent moisture-proof film thereon, the electrode layer surface or the moisture-proof film is protected. Adhesion to the film surface is extremely strong, and a uniform uneven shape can be formed.

By forming the uneven shape in this way, it is possible to reduce the reflectance of light on the incident side, and the characteristics similar to those in the case where the uneven shape is formed by a conventional method such as mixing of fine particles may cause a characteristic change. It is possible to improve. Although it is conceivable to form a light-scattering polymer film on the surface side of the transparent moisture-proof film, it is not preferable because it cannot be expected in terms of reflectance, weather resistance and the like.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings in which common portions are given the same reference numerals. 1, 2, and 3
FIG. 3 is a cross-sectional view showing the structures of thin film solar cells of Example 1, Example 2 and Example 3 of the present invention, which will be described below.

In FIG. 1, a first electrode layer 2 made of metal, a thin film semiconductor layer 3 having a pin junction, and a transparent second electrode layer 4 made of ITO or the like are provided on one surface of a flexible plastic film substrate 1. Are laminated, and the third electrode layer 5 described in, for example, Japanese Patent Application No. 5-67976 is formed on the other surface side, and the first electrode layer 2 is formed through a through hole (not shown) formed in the substrate 1. Alternatively, it is connected to the second electrode layer 4. The light-scattering polymer film 6 having an uneven shape is formed on the second electrode layer 4 of the solar cell having such a structure. Further, the light-scattering polymer film 6 is sandwiched by a transparent moisture-proof film 81 with a transparent adhesive layer 71 interposed therebetween, and a moisture-proof film 82 with an adhesive layer 72 interposed on the third electrode layer 5. There is.

In FIG. 2, the light-scattering polymer film 6 is inserted between the transparent adhesive layer 71 and the transparent moisture-proof film 81, and in FIG. 3, the light-scattering polymer film 6 is the transparent adhesive layer 7.
It is inserted on both sides of 1. 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, polyethersulfone, polyphenylene sulfide, para-type aramid, polyetherketone, or a fluorine-based film in general, but especially polyimide, para-type Aramid and fluorine-based films are suitable. 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. The electrode layers 2, 4, and 5 are a metal film, a transparent conductive film, and
A metal film is formed by means such as sputtering.

As the moisture-proof film 81 on the light incident side, a transparent plastic film having a low water 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 82 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 films, a metal foil made of aluminum or the like is sandwiched with a plastic film. Even if the plastic film itself has a slightly high water permeability, a metal foil sandwiched with the plastic film is used. Therefore, it is possible to use a material that blocks invading water.

The materials used for the adhesive layers 71 and 72 are
Nylon-12, polyvinyl alcohol (PVA), polyvinyl butyral (PVB), polyolefin-based ethylene-vinyl acetate copolymer (EVA), vinyl chloride copolymer, propylene copolymer, acrylonitrile copolymer and the like can be mentioned. The light-scattering polymer film 6 is made of polymethylmethacrylate (PMMA), methylmethacrylate.
(MMA), ethyl acrylate, ethylene, propylene, acrylonitrile, styrene, vinyl chloride, vinyl acetate, maleic acid and other monomers and polymers are used, for example, copolymerization of monomers having different compatibility, or PMMA
A polymer having a refractive index different from that of a resin is dissolved in a small amount of MMA monomer and polymerized to give an uneven shape when solidified.

Embodiment 1 This embodiment shown in FIG. 1 is an embodiment of claim 2. A polyimide film (manufactured by Toray DuPont, trade name: Kapton) is used as the film substrate 1, and the first electrode layer 2 is A
g film, an amorphous silicon film having a pin junction as the thin film semiconductor layer 3, an ITO film as the second electrode layer 4, and an Ag film as the third electrode layer 5 on the back side of the insulating substrate 1 by a predetermined device. Then, it was used as a solar cell.

Subsequently, a small amount of an acrylonitrile polymer is dissolved in a methyl methacrylate monomer to be polymerized, and this polymerized solution is applied onto the second electrode layer 4 and solidified to form an unevenness of about 2 μm. A light-scattering polymer film 6 having a shape was formed. After that, the adhesive layers 71 and 72 are formed to a thickness of 400 μm by EVA, and the moisture-proof films 71 and 72 are formed.
As a thin film, a polyphenylene sulfide film (manufactured by Toray Industries, Inc., trade name: Torelina) having a thickness of 50 μm was set on both sides of the solar cell, and laminated at a temperature of 130 ° C. for 10 minutes under vacuum heating and pressing conditions. A solar cell was produced.

Embodiment 2 This embodiment shown in FIG. 2 is an embodiment of claim 3. In this thin-film solar cell, a thin-film solar cell was prepared in the same manner as in Example 1 except that the position of the light-scattering polymer film 6 on the second electrode layer 4 in Example 1 was changed to the back surface side of the transparent moisture-proof film 81. It was made.

Example 3 This example shown in FIG. 3 is an example of claim 4, which is on the second electrode layer 4 of Example 1 and the transparent moisture-proof film 71 of Example 2.
Light-scattering polymer film 6 having irregularities on the back side of the
Was formed, and a thin film solar cell was prepared in the same manner as in Example 1 except for the above. Comparative Example A thin film solar cell having a conventional structure was produced in the same manner as in Example 1 except that the light scattering polymer film 6 was omitted.

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 characteristics can be evaluated. As a result of measuring the initial electrical characteristics of the above Examples 1 to 3 and Comparative Example, about 10% conversion efficiency was improved in Examples 1 to 3 as compared with Comparative Example. Further, in the example, it was observed that the reflectance decreased due to the effect of the uneven shape and the current increased. Furthermore, the thin film solar cell without an external lead wire produced at the same time was cut and a peeling test was performed. As a result, the comparative example peeled relatively easily, but the example did not peel easily.

From the above, it can be seen that the thin-film solar cells of the examples of the present invention have improved initial characteristics and superior adhesion as compared with the comparative examples. In the above examples, the example is a thin film solar cell in which the third electrode layer is formed on the surface of the substrate,
It is obvious that the present invention is also effective when applied to a thin film solar cell configured only on one surface of a substrate, that is, a thin film solar cell having no third electrode layer.

[0020]

According to the present invention, a light-scattering polymer film having an uneven shape is formed between the moisture-proof film on the surface and the transparent second electrode layer in order to reduce the surface reflectance of incident light to the solar cell. By inserting, since the light-scattering polymer film has good adhesion to both the moisture-proof film and the second electrode layer, it has become possible to manufacture thin-film solar cells with improved photoelectric conversion efficiency at a high yield rate. .

[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 sectional view showing the structure of a thin film solar cell according to another embodiment of the present invention.

FIG. 3 is a sectional view showing the structure of a thin-film solar cell according to still another embodiment of the present invention.

[Explanation of symbols]

 1 film substrate 2 first electrode layer 3 thin film semiconductor layer 4 transparent second electrode layer 5 third electrode layer 6 light scattering polymer film 71 transparent adhesive layer 72 adhesive layer 81 transparent moisture-proof film 82 moisture-proof film

Claims (4)

[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 a light-scattering polymer film is inserted between the transparent second electrode layer and the moisture-proof film. A thin film solar cell characterized by the above. 2. The thin film solar cell according to claim 1, wherein the light-scattering polymer film is in contact with the transparent second electrode layer. 3. The thin-film solar cell according to claim 1, wherein the light-scattering polymer film is in contact with the moisture-proof film. 4. The thin-film solar cell according to claim 1, wherein the light-scattering polymer film has two layers, one layer is in contact with the transparent second electrode layer, and the other one layer is in contact with the moisture-proof film.