Background Art A solar cell absorbs radiant energy of sunlight and converts it directly into electric power. In order to efficiently absorb radiant energy of sunlight, it is desirable that a solar cell module should be installed on a roof having a curved surface, a cylindrical structure, or the like. Thus, there has heretofore been a demand for disposing a solar cell module on a surface of a curved structure to efficiently convert solar radiation into electric power. For example, a solar cell which can be installed on a surface of a curved structure can be manufactured by depositing an amorphous solar cell on a sheet having a curved surface. However, an amorphous solar cell has been disadvantageous in that the efficiency of converting solar radiation into electric power is so low that large electric power cannot be generated in a relatively small area.

On the other hand, a solar cell having a monocrystalline or polycrystalline silicon substrate can highly efficiently convert solar radiation into electric power. Generally, a solar cell having a crystalline silicon substrate is so thick that it cannot easily be bent. For this reason, solar cell modules available on the market have utilized a flat plate-shaped crystalline silicon substrate. If solar cell

modules can be formed not only into a flat shape, but also into a curved shape, then they can be installed at many more sites than if they are limited to a flat shape.

Disclosure of Invention The present invention has been made in view of the above drawbacks. It is, therefore, an object of the present invention to provide a solar cell module which can be installed on a surface of a curved structure and can highly efficiently convert solar radiation into electric power, and a method of manufacturing such a solar cell module.

According to a first aspect of the present invention, there is provided a solar cell module comprising a metallic thin plate and a solar cell composed of a crystalline substrate having a thickness of 200 um or less. The solar cell is fixed on the metallic thin plate.

According to a second aspect of the present invention, there is provided a solar cell module comprising a thermoplastic thin plate and a solar cell composed of a crystalline substrate having a thickness of 200 um or less.

The solar cell is fixed on the thermoplastic thin plate.

The crystalline substrate may comprise a crystalline silicon substrate. The solar cell may be bonded to the metallic or thermoplastic thin plate by an adhesive. Further, the solar cell may comprise a transparent film attached on a front face thereof. The transparent film should preferably provide weather resistance. Furthermore, the solar cell may comprise an insulating sheet interposed between a rear face of the solar cell and the metallic or thermoplastic thin plate.

According to a third aspect of the present invention, there is provided a method of manufacturing a solar cell module. A transparent surface cover member, a first adhesive,

a solar cell composed of a crystalline substrate, a second adhesive, an insulating sheet, and a metallic or thermoplastic thin plate are stacked to form a laminated structure. The laminated structure is heated and bonded to soften the first adhesive and the second adhesive. The laminated structure is formed into a desired curved shape while the first adhesive and the second adhesive are softened.

The laminated structure is cooled to harden the first adhesive and the second adhesive. The crystalline substrate may comprise a crystalline silicon substrate.

The heating should preferably be performed under a vacuum. The forming may be performed after the heating.

Alternatively, the forming and the heating may be performed simultaneously.

According to the present invention, since a (semiconductor) crystalline substrate in a solar cell is extremely thin, for example, as thin as 200 um or less, the solar cell can be deformed in accordance with a curved structure of the metallic or thermoplastic thin plate and can be fixed on the curved surface of the metallic or thermoplastic thin plate. Thus, it is possible to form a solar cell module having a curved structure which utilizes a crystalline substrate having a high efficiency of converting solar radiation into electric power. Since the crystalline substrate in the solar cell adheres to the thermoplastic thin plate, the solar cell module having a curved structure can be formed stably without adverse influence on the electric characteristics thereof.

The above and other objects, features, and advantages of the present invention will be apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example.

Brief Description of Drawings FIG. 1 is a cross-sectional view showing a solar cell module according to an embodiment of the present invention; and FIGS. 2A through 2C are cross-sectional views explanatory of a method of manufacturing a solar cell module according to an embodiment of the present invention, wherein FIG. 2A shows a laminated structure in which adhesive resin sheets are inserted into materials for a solar cell module, FIG. 2B shows a laminated solar cell module formed by heating and bonding the laminated structure, and FIG. 2C shows the laminated solar cell module formed into a curved shape with dies having curved shapes.

Best Mode for Carrying Out the Invention A solar cell module according to an embodiment of the present invention will be described below with reference to FIG. 1.

FIG. 1 is a cross-sectional view showing a solar cell module 10 according to an embodiment of the present invention.

As shown in FIG. 1, the solar cell module 10 has a curved structure (structure having curved surfaces) in the form of an arch. The solar cell module 10 has a solar cell 11 of a crystalline silicon substrate and a metallic thin plate 12.

The solar cell 11 has a surface cover member 13 disposed on a front face thereof, and an insulating resin sheet 14 interposed between a rear face of the solar cell 11 and the metallic thin plate 12. The solar cell 11 with the insulating resin sheet 14 is fixed on the metallic thin plate 12 so as to closely contact the metallic thin plate 12. The surface cover member 13 may comprise a transparent film having weather resistance. The solar cell 11 comprises a monocrystalline

or polycrystalline silicon substrate having a thickness of 200 um or less.

The crystalline silicon substrate of the solar cell 11 has pn junctions therein. When light is applied to the pn junctions in the crystalline silicon substrate, the pn junctions generate electric power and output the electric power via a cable (not shown). Thus, the solar cell 11 outputs electric power from the pn junctions in the crystalline silicon substrate. In this manner, the solar cell module 10 can highly efficiently convert solar radiation into electric power.

A relatively thin crystalline silicon substrate having a thickness of 200 um or less can easily be deformed.

Therefore, when such a relatively thin crystalline silicon substrate is utilized for a solar cell module, the solar cell module can be formed into a curved structure, for example, a semicircular arc structure as shown in FIG. 1.

A solar cell utilizing such a relatively thin crystalline silicon substrate may be manufactured by methods disclosed in Japanese patent applications Nos. 11-125064 and 2000-275315 assigned to the assignee of this patent application, which are hereby incorporated by reference.

Although a single crystalline silicon substrate is used for a solar cell in FIG. 1, a plurality of crystalline silicon substrates may be used for a solar cell and connected to each other via cables.

The metallic thin plate 12 for supporting the solar cell 11 should preferably comprise a stainless steel plate having a thickness ranging from about 0.1 mm to about 0.5 mm. Since the metallic thin plate 12 has plasticity with respect to its shape, it can be formed into a desired shape.

The surface cover member 13 for protecting the front face of the solar cell 11 may comprise a transparent film

having weather resistance and may have a thickness ranging from about 50 um to about 200 um. The surface cover member 13 serves to protect the solar cell 11 from being exposed to the weather.

The insulating resin sheet 14 disposed between the rear face of the solar cell 11 and the metallic thin plate 12 has a thickness ranging from about 50 um to about 200 um. The insulating resin sheet 14 serves to electrically insulate the solar cell 11 from the metallic thin plate 12.

The surface cover member 13, the solar cell 11, the insulating resin sheet 14, and the metallic thin plate 12 are strongly bonded to each other by a thermosetting resin adhesive to form the solar cell module 10 as a whole. Since the metallic thin plate 12 is used so as to closely contact the solar cell 11, the metallic thin plate 12 is plastically deformed together with the solar cell 11 by press forming or the like to form a solar cell module having a stable curved structure. Even if the solar cell 11 is deformed so as to have curved surfaces, the electric characteristics thereof are not influenced by the deformation.

As described above, the solar cell module 10 has a curved structure, which has a radius of curvature of about 50 mm.

Therefore, the solar cell module 10 can be installed on a pole of a windmill power generator or a utility pole, for example. Since the solar cell module 10 can be installed in such places, a high efficiency of converting solar radiation into electric power can be achieved without spoiling the beauty of the surrounding architecture. Although the solar cell module 10 has a semicircle cross section in FIG. 1, the solar cell module 10 may have various cross sections. As long as the radius of curvature of the cross section is larger than about 50 mm, it is possible to form the solar cell module 10 into a desired curved structure. For example, the solar

cell module 10 can be formed into the form of a roof tile or the like. Specifically, the solar cell module 10 can be formed into a desired shape in accordance with a location at which the solar cell module 10 is installed.

A method of manufacturing the solar cell module 10 will be described below with reference to FIGS. 2A through 2C.

As shown in FIG. 2A, materials for a solar cell module are stacked on each other to form a laminated structure.

Specifically, a stainless steel sheet having a thickness of about 0.1 mm, for example, is disposed as a metallic thin plate 12 at a lowermost position. A sheet-like resin adhesive 16a such as ethylene-vinyl acetate (EVA) is applied onto the metallic thin plate 12. An insulating resin sheet 14 of a fluorine material having a thickness ranging from about 50 um to 200 um is disposed on the resin adhesive 16a.

A resin adhesive 16b is applied onto the insulating resin sheet 14, and a solar cell 11 composed of a crystalline silicon substrate is disposed thereon. A resin adhesive 16c is applied onto the solar cell 11, and a weather-resistant resin sheet of a fluorine material having a thickness ranging from about 50 um to 200 um is disposed thereon as a surface cover member 13. The surface cover member 13 and the resin adhesive 16c, which are located on the front face of the solar cell 11, comprise a transparent material so as to allow sunlight to be applied to the solar cell 11.

Next, the laminated structure of the materials for the solar cell module is heated and compressed to bond the materials to each other. Thus, as shown in FIG. 2B, a laminated solar cell module is formed. Specifically, for example, the laminated structure of the materials for the solar cell is sandwiched between metallic plates 20a and 20b, which are heated to a temperature ranging from about 80°C to about 200°C, under a vacuum. Both of the metallic plates

20a and 20b are pressed against each other, or one of the metallic plates 20a and 20b is pressed against the other of the metallic plates. When the laminated structure is thus heated, the resin adhesives 16a, 16b, and 16c are softened to bond the surface cover member 13, the solar cell 11, the insulating resin sheet 14, and the metallic thin plate 12 to each other. Since the laminated structure is heated and bonded under a vacuum, air bubbles are evacuated from spaces between the respective materials (respective sheets) so that the respective materials (respective sheets) can adhere to each other.

Next, as shown in FIG. 2C, the laminated solar cell module is sandwiched between two dies 21a and 21b having predetermined curved shapes. Then the dies 21a and 21b are pressed to each other to deform the laminated solar cell module so as to follow the curved shapes of the dies 21a and 21b. It is desirable that forming of the laminated solar cell module into the curved shape is performed before the resin adhesives 16a, 16b, and 16c harden, after being softened by the aforementioned heating process. The dies 21a and 21b are preheated to a temperature ranging from about 50°C to about 150°C, and then the laminated solar cell module is formed into a curved shape while the resin adhesives 16a, 16b, and 16c are softened. Thereafter the laminated solar cell module is slowly cooled by self-cooling or forcedly cooled by water-cooling or air-cooling to harden the resin adhesives 16a, 16b, and 16c, so that plastic deformation of the metallic thin plate 12 and the solar cell 11 is caused. The plastic deformation of the metallic thin plate 12 and the solar cell 11, together with hardening of the resin adhesives 16a, 16b, and 16c, allows the solar cell module 10 to have a rigid curved structure.

Even if the resin adhesives 16a, 16b, and 16c are

hardened after the aforementioned heating process, the resin adhesives 16a, 16b, and 16c can be softened by reheating during the aforementioned forming process. The forming process of the laminated solar cell module may be performed after the resin adhesives 16a, 16b, and 16c are softened by reheating.

With the above method, the solar cell module 10 can be formed into a curved structure having a radius of curvature as small as about 50 mm. Therefore, a solar cell module can be formed into a shape having a desired curved surface by dies prepared in advance. Since the solar cell module can be formed into a desired curved structure, the solar cell module can be installed on a pole of a windmill power generator or a utility pole having a curved shape. Since the solar cell module comprises a crystalline silicon substrate, the solar cell module can highly efficiently convert solar radiation into electric power.

The surface cover member 13 disposed on a front face of the solar cell module 10 has a large thermal expansion coefficient. Therefore, when the surface cover member 13 is thermally expanded and shrunk repeatedly, it may cause elements in the solar cell to be greatly damaged. In the present embodiment, the metallic thin plate 12 disposed on a rear face of the solar cell module 10 prevents such damage.

Further, the metallic thin plate 12 disposed on the rear face of the solar cell module 10 also prevents wrinkling from being produced in the solar cell module 10 during the forming process of the solar cell module 10.

As described above, in the illustrated example shown in FIGS. 2A through 2C, the laminated structure of materials for a solar cell module is formed into a plate shape, then heated and bonded with the plate shape, and formed into a curved shape. The heating process of the plate-shaped

laminated structure, as described in connection with FIG.

2B, may be omitted. Specifically, the plate-shaped laminated structure shown in FIG. 2A may be formed directly into the curved shape with the dies 21a and 21b while the laminated structure is heated.

The surface cover member 13, the solar cell 11, and the insulating resin sheet 14 may be preheated, and the solar cell 11 with the surface cover member 13 and the insulating resin sheet 14 may be deformed into a curved shape into which the metallic thin plate 12 is preformed, and attached onto the metallic thin plate 12 by a resin adhesive (sheet).

In the present embodiment, the solar cell 11 comprises a monocrystalline or polycrystalline silicon substrate. The solar cell 11, however, may comprise a crystalline substrate of a compound semiconductor, for example.

Although the metallic thin plate 12 comprises a stainless steel plate having a thickness ranging from about 0.1 mm to about 0.5 mm, the metallic thin plate 12 may have a thickness ranging from about 0.01 mm to about 0.5 mm as long as a crystalline silicon substrate of a solar cell can be formed into a desired curved shape and can be held in the curved shape stably. The material of the metallic thin plate 12 is not limited to stainless steel, and may be an alloy of iron, aluminum, or galvanium. Fluororesin may be coated on the metallic thin plate 12. Although a metallic thin plate having plasticity is used in the present embodiment, a material that has plasticity and is not decomposed by heating at a temperature of about 150°C may be used instead of the metallic thin plate. For example, a thermoplastic resin, thermoplastic elastomer, or the like may be used as a substitute for the metallic thin plate. The thermoplastic resin includes general plastics such as polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polystyrene

(PS), acrylonitrile butadiene styrene (ABS), butadiene styrene, and polybutadiene, acrylic rubber type methyl methacrylate butadiene styrene (MBS) resin, copolymer resin of styrene monomer and acrylonitrile (AS), polymethyl methacrylate (PMMA), copolymer of methyl methacrylate and styrene (MS), polyvinyl alcohol (PVA), polyvinylidene chloride (PVDC), polyethylene terephthalate (PET), engineering plastics such as polyamide (PA), polyacetal (POM), polycarbonate (PC), polyphenylene ether (PPE (denatured <BR> <BR> PPO) ), polybutylene terephthalate (PBT), ultra high molecular weight polyethylene (UHMW-PE), and polyvinylidene fluoride (PVDF), and super engineering plastics such as polysulfone (PSF), polyethersulfone (PES), polyphenylene sulfide (PPS), polyarylate (PAR), polyamide imide (PAI), polyether imide (PEI), polyether ether ketone (PEEK), polyimide (PI), liquid crystal polymer (LCP), and polytetrafluoroethylene (PTFE).

As described above, according to the present invention, a solar cell module can highly efficiently convert solar radiation into electric power and can be installed on a curved structure having a curved surface so as to closely contact the curved surface.

Although certain preferred embodiments of the present invention have been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.

Industrial Applicability The present invention is suitable for use in a solar cell module having a solar cell composed of a thin-film semiconductor crystal substrate with a curved structure.