Solar cell module and method of manufacturing the same

A solar cell module includes a base body, a plurality of solar cell elements arranged at intervals over the base body, a resin layer disposed on the solar cell elements and comprising a plurality of recesses on its surface facing opposite to the solar cell elements, and a protective sheet disposed on the resin layer. The protective sheet comprises a plurality of protrusions which correspond to the recesses of the resin layer and which are in contact with the recesses. The height of first protrusion at a location corresponding to the interval between the solar cell elements among the plurality of protrusions is higher than the height of second protrusion at a location corresponding to the solar cell element among the plurality of protrusions. The interval between adjacent ones of the second protrusions in a portion corresponding to an end portion of the base body in longer than the interval between adjacent ones of the second protrusions in a portion corresponding to a central portion of the base body.

CROSS-REFERENCE TO THE RELATED APPLICATIONS

This application is a national stage of international application No. PCT/JP2009/054815 filed on Mar. 12, 2009, and claims the benefit of priority under 35 USC 119 to Japanese Patent Application No. 2008-063108, filed on Mar. 12, 2008, the entire contents of which are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a solar cell module and a method of manufacturing the same.

BACKGROUND ART

With the recent increasing momentum toward environmental protection, the market for a solar cell module is expanding.

Enlargement in the size of the solar cell module is demanded, in order to obtain higher photoelectric conversion energy.

Additionally, in recent years, it is demanded that a main surface of the solar cell module be formed as a curved surface, in order to obtain a design in which an installation object and the solar cell module are integrated with each other.

However, there is for example a problem that, in forming a large-size solar cell module, members exhibit thermal expansion and contraction during integration of the members, to cause a misalignment or the like among the members, which tends to promote occurrence of wrinkles in a back-surface sheet.

There is also a problem that, when a solar cell module whose main surface has a curved surface is formed in the above-described embodiment, a remaining part of a back-surface sheet not conforming a curved surface of a light-transmitting subs hate forms wrinkles or rises up from a cross-linkable resin during integration of members. Particularly, the tendency to cause wrinkles or stay of air within wrinkles is higher at an end portion of the back-surface sheet. There is a problem that wrinkles occurring in the back-surface sheet easily allow entrance of oxygen and moisture therethrough, so that the cross-linkable resin is yellowed or absorbs moisture to consequently deteriorate.

DISCLOSURE OF THE INVENTION

A solar cell module and a method of manufacturing the same according to the present invention mainly aim at reducing the above-described wrinkles of the back-surface sheet.

A solar cell module according to an embodiment of the present invention includes: a base body; a plurality of solar cell elements arranged at intervals over the base body; a resin layer disposed on the solar cell elements and having a plurality of recesses on its surface facing opposite to the solar cell elements; and a protective sheet disposed on the resin layer. The protective sheet has a plurality of protrusions which correspond to the recesses of the resin layer and which are in contact with the recesses. The height of first protrusion at a location corresponding to the interval between the solar cell elements among the plurality of protrusions is higher than the height of second protrusion at a location corresponding to the solar cell element among the plurality of protrusions, the interval between adjacent ones of the second protrusions in a portion corresponding to an end portion of the base body is longer than the interval between adjacent ones of the second protrusions in a portion corresponding to a central portion of the base body.

In this solar cell module, stress caused by a difference among members in the length of thermal expansion and contraction can be efficiently relieved by the protrusions of the protective sheet. Thus, stress which may cause wrinkles in the protective sheet can be reduced.

A solar cell module according to an embodiment of the present invention includes: a base body; a plurality of solar cell elements arranged at intervals over the base body; a resin layer disposed on the solar cell elements and having a plurality of recesses on its surface facing opposite to the solar cell elements; and a protective sheet disposed on the resin layer. The protective sheet has a plurality of protrusions which correspond to the recesses of the resin layer and which are in contact with the recesses. The height of first protrusion at a location corresponding to the interval between the solar cell elements among the plurality of protrusions is higher than the height of second protrusion at a location corresponding to the solar cell element among the plurality of protrusions, the height of said second protrusion located in a portion corresponding to an end portion of said base body is higher than the height of the second protrusion located in a portion corresponding to a central portion of the base body.

In this solar cell module, stress caused by a difference among members in the length of thermal expansion and contraction can be efficiently relieved by the protrusions of the protective sheet. Thus, stress which may cause wrinkles in the protective sheet can be reduced.

A method of manufacturing a solar cell module according to an embodiment of the present invention includes the steps of: preparing a module laminate which is formed by a solar cell element, a resin layer, and a protective sheet being put in layers in the mentioned order on a base body; forming a plurality of protrusions on a surface of the resin layer side of the protective sheet; and heating the resin layer in order to cure the resin layer, wherein the heating the resin layer is performed simultaneously with the forming the plurality of protrusions or after the step of forming the plurality of protrusions.

In this method of manufacturing a solar cell module, the plurality of protrusions formed in the protective sheet provide unevenness which can reduce large wrinkles occurring in the protective sheet.

BEST MODE FOR CARRYING OUT THE INVENTION

First Embodiment

<1-1. Configuration of Solar Cell Module>

Firstly, a configuration of a solar cell module100according to a first embodiment of the present invention is described.

FIG. 1Ais a cross-sectional view showing the configuration of the solar cell module100according to the first embodiment of the present invention.FIG. 1Bis a plan view showing a solar cell string11in the solar cell module100.FIG. 1Cis a plan view showing a configuration of a string assembly12having a plurality of solar cell strings11coupled to one another in the solar cell module100.

The solar cell module100mainly includes a light-transmitting substrate4, a resin layer5, and a back-surface sheet9. The resin layer5is formed on the light-transmitting substrate4so as to seal the string assembly12. The back-surface sheet9is formed on the resin layer5.

The solar cell string11includes a plurality of solar cell elements6, and connecting conductors8which electrically connect positive electrodes and negative electrodes of the adjacent solar cell elements6. The plurality of solar cell elements6are connected in series with one another by the connecting conductors8.

The string assembly12includes a plurality of solar cell strings11, and a plurality of coupling electrodes7which connect end portions of the adjacent solar cell strings11. Each of the solar cell strings11is connected in series with the adjacent solar cell string11by the coupling electrode7.

In this connecting manner, all the solar cell elements6are electrically connected in series with one another in the string assembly12.

Next, each component of the solar cell module100is described.

The light-transmitting substrate4serves as a base body. Therefore, a material of the light-transmitting substrate4is not particularly limited, as long as the light-transmitting substrate4is a member capable of transmitting an incident light therethrough to the solar cell elements6. However, it is preferable to use a member having a high light transmittance which is made of a glass such as a white glass, a toughened glass, and a heat-reflecting glass, or a polycarbonate resin, etc. Preferably, the thickness of the light-transmitting substrate4is, for example, approximately 3 mm to 5 mm when a white toughened glass is used, and approximately 5 mm when a synthetic resin substrate (made of a polycarbonate resin or the like) is used.

The resin layer5serves to seal the solar cell elements6. In this embodiment, the resin layer5is formed as an integration of a first resin layer5aand a second resin layer5b. As the resin layer5, it is preferable to use a cross-linkable resin such as a thermosetting resin or a resin having thermosetting characteristics which is obtained by adding a cross-linking agent to a thermoplastic resin. It is preferable that each of the first resin layer5aand the second resin layer5bhas a thickness of approximately 0.4 to 1 mm. As this resin layer5, for example, the above-mentioned cross-linkable resin which is formed into a sheet shape by an extruder and then is cut may be used. The resin layer5has a plurality of recesses formed on a surface thereof facing opposite to the solar cell element6side. In this embodiment, the recesses are formed in the second resin layer5b.

For example, an acrylic resin, a silicon resin, an epoxy resin, and the like, may be used as the thermosetting resin.

Preferably, the thermoplastic resin has, as a main component, ethylene-vinyl acetate copolymer (EVA), polyvinyl butyral (PVB), ethylene-ethyl acrylate copolymer (EEA), and the like, for example. The cross-linking agent serves to link molecules of the thermoplastic resin. For example, an organic peroxide which decomposes at a temperature of 70 to 180° C. to generate a radical may be used as the cross-linking agent. As the organic peroxide, for example, 2,5-dimethyl-2,5-bis(t-butylperoxy)hexane, tert-hexyl peroxypivalate, or the like, may be used. It is preferable that the organic peroxide is contained at a ratio of approximately one part by mass to 100 parts by mass of EVA, for example.

From the viewpoint of improving a performance of transmitting a light to the solar cell elements6, it is preferable that a material having a high light transmissivity is used as the first resin layer5a. On the other hand, from the viewpoint of improving a design in accordance with the installation environment of the solar cell module100, a material to which a titanium oxide, a pigment, or the like, is added and which is thereby given a desired color may be used as the second resin layer5b.

For example, a single-crystal or poly-crystal silicon substrate is used as the solar cell elements6. The silicon substrate may have a thickness of approximately 0.2 to 0.3 mm, and a size of approximately 150 to 160 mm square, for example. The silicon substrate has a PN junction provided by a P-type semiconductor layer and an N-type semiconductor layer being bonded to each other. The P-type semiconductor layer has a high content of P-type impurities such as boron. The N-type semiconductor layer has a high content of N-type impurities such as phosphorus. The silicon substrate has, on its front surface and/or back surface, an electrode which is made of a silver paste or the like and formed by a screen-printing method or the like. For the purpose of protection of the electrode or ease of mounting the connecting conductor8to the electrode, substantially the entire surface of the electrode may be coated with a solder.

The solar cell element6is not limited to the above-described one using the crystal silicon substrate of the single-crystal or the poly-crystal silicon. Various solar cell elements may be used, such as an amorphous silicon type, an Si thin film type, a CIS type, a CIGS type, or a dye sensitized type.

(Connecting Conductor and Coupling Electrode)

It is preferable to use, as the connecting conductor8, a wire material such as a copper foil which has the entire surface thereof coated with a solder of approximately 20 to 70 μm by means of plating or dipping, for example. For example, in a case where the solar cell element6using a poly-crystal silicon substrate of 150 mm square is used, the connecting conductor8preferably has a width of approximately 1 to 3 mm and a length of approximately 260 to 290 mm.

Preferably, similarly to the connecting conductor8, the coupling electrode7is made of a copper foil and has the entire surface thereof coated with a solder, and has a width of approximately 4 to 8 mm.

The back-surface sheet9serves as a protective sheet protecting the resin layer5and the solar cell elements6, and is a sheet made of polyvinyl fluoride (PVF), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or the like, or a lamination thereof.

The thickness of the back-surface sheet9is, for example, approximately 10 μm to 50 μm, and preferably is 20 μm to 40 μm from the viewpoint of sufficiently ensuring a humidity resistance, weatherability, and the like, and further simplifying a transfer of unevenness which is described later.

A surface of the back-surface sheet9facing the solar cell element6has an unevenness including a plurality of protrusions. The protrusions are formed at positions corresponding to the recesses of the resin layer5, so as to be in contact with inner surfaces of the recesses of the resin layer5. Additionally, in the back-surface sheet9, a protrusion at a location corresponding to an interval between the adjacent solar cell elements6with respect to an arrangement direction is higher than a protrusion at a location corresponding to an area where the solar cell element6is placed.

A reflecting member may be provided on the light-receiving surface side of the back-surface sheet9. To form the reflecting member, for example, aluminium or the like is vapor-deposited on a light-receiving surface of the back-surface sheet9. Thereby, a light incident through the interval between the adjacent solar cell elements6is diffusely reflected by the reflecting member, and this reflected light can also contribute to a photoelectric conversion. This can increase a power generation efficiency.

In the solar cell module100having the above-described configuration, as shown inFIG. 1A, the protrusions of the back-surface sheet9at the locations corresponding to the intervals between the adjacent solar cell elements6are high, as compared with the protrusions of the back-surface sheet9at the locations corresponding to the areas where the solar cell elements6are placed. Thus, the unevenness of the surface of the back-surface sheet9on which these protrusions are formed is large. That is, the solar cell module100is structured such that the protrusions of the back-surface sheet9protruding toward the light-transmitting substrate4side go deeper into the resin layer5in the regions corresponding to the areas above the intervals between the adjacent solar cell elements6than in the regions corresponding to the areas above the respective solar cell elements6. In this solar cell module100, the protrusions of the back-surface sheet9are made large at the locations corresponding to where the solar cell elements6are not placed, which increases the degree of freedom in the deformation of these protrusions, so that the stress caused by the difference among the members in the length of thermal expansion and contraction can be efficiently relieved.

<1-2. Structure of Laminating Apparatus>

Next, a structure of a laminating apparatus2which is used in manufacturing the solar cell module100according to the first embodiment of the present invention is described.

FIG. 2is a cross-sectional view showing a structure of the laminating apparatus2in which a module laminate10is placed.FIG. 3is a cross-sectional view enlarging the module laminate10shown inFIG. 2to show a configuration of the module laminate10. The module laminate10has a configuration in which the first resin layer5a, the string assembly12, the second resin layer5b, and the back-surface sheet9are stacked in the mentioned order on a non-light-receiving surface of the light-transmitting substrate4.

The laminating apparatus2mainly includes a housing13, a diaphragm sheet15, a heater board18, and a pressing member3. The housing13includes an upper housing13aand a lower housing13bwhich are mutually openable and closable. The diaphragm sheet15divides the interior of the housing13into an upper vacuum region14aand a lower vacuum region14b. The heater board18is positioned substantially at the center of the interior of the lower housing13b. The pressing member3is positioned between the diaphragm sheet15and the heater board18.

An upper vacuum pump16ais connected to the upper housing13a, so that the pressure of the upper vacuum region14asurrounded by the upper housing13aand the diaphragm sheet15can be reduced by actuating the upper vacuum pump16a. Similarly, a lower vacuum pump16bis connected to the lower housing13b, so that the pressure of the lower vacuum region14bsurrounded by the lower housing13band the diaphragm sheet15can be reduced by actuating the lower vacuum pump16b.

It is preferable that a resin member such as a silicon rubber having excellent strength and stretchability is used for the diaphragm sheet15.

A heater18ais connected to the heater board18, so that the module laminate10placed on the heater board18can be heated by applying voltage to the heater18a.

The pressing member3is a member for forming, on the back-surface sheet9, unevenness including a plurality of protrusions. The pressing member3has, for example, a resin sheet such as a silicon rubber sheet, a sheet-like textile, or the like. A surface (pressing surface) of the pressing member3which presses the back-surface sheet9has unevenness, in order to form a plurality of protrusions on the back-surface sheet9. Using such a pressing member3can improve the reliability in integrating the module laminate10. If a textile formed with glass fibers and impregnated with a fluorine resin such as polytetrafluoroethylene is used as the pressing member3, a mold releasability of the back-surface sheet9and the resin layer5from the pressing member3can be improved.

Using such a pressing member3can improve the reliability in integrating the module laminate10. If a textile formed with glass fibers and impregnated with a fluorine resin such as polytetrafluoroethylene is used as the pressing member3, a mold releasability of the back-surface sheet9and the resin layer5from the pressing member3can be improved.

If a textile is used as the pressing member3, unevenness formed by its texture is transferred to the back-surface sheet9in a later-described step. It is preferable that a pitch of the unevenness of the texture with respect to the horizontal direction is approximately 500 μm to 1500 μm. Additionally, it is preferable that a difference in height of the unevenness with respect to the vertical direction is approximately 30 μm to 200 μm from the viewpoint of enabling accurate transfer while reducing a load applied to the solar cell elements6during pressing.

In the laminating apparatus2, for the purpose of relieving impact applied to the module laminate10during the manufacturing process, an urethane rubber (not shown) and a mold release sheet21may be provided in the mentioned order on the heater board18. Furthermore, the mold release sheet21may also be provided on the pressing member3. The mold release sheet21can inhibit the first resin layer5aand the second resin layer5b, which may leak out between the light-transmitting substrate4and the back-surface sheet9, from adhering to the interior of the laminating apparatus2.

<1-3. Method of Manufacturing Solar Cell Module>

Next, a method of manufacturing the solar cell module100according to the first embodiment of the present invention is described. In the following description, a case where a cross-linkable resin obtained by a cross-linking agent being contained in a thermoplastic resin is used for the resin layer5(the first resin layer5aand the second resin layer5b) is taken as an example.

Firstly, a step of press-heating the module laminate10in the laminating apparatus2is described.FIGS. 4 to 6are diagrams showing, step-by-step, a state in the middle of the press-heating of the module laminate10in the laminating apparatus2.

The upper housing13aof the laminating apparatus2is first moved up to open the housing13, and in this state, the module laminate10is placed on the mold release sheet21which is disposed on the heater board18in the lower housing13bsuch that the light-transmitting substrate4faces downward.

Then, the pressing member3and the mold release sheet21are layered in the mentioned order on the back-surface sheet9of the module laminate10. Then, the upper housing13ais moved down toward the lower housing13bside, to close the housing13. Thus, the module laminate10is mounted in the laminating apparatus2(FIG. 4).

Then, the press-heating step is performed in which pressing is performed under a pressure condition allowing the unevenness of the pressing member3to be transferred to the back-surface sheet9and at the same time heating is performed under a temperature condition equal to or higher than a cross-linking temperature of the second resin layer5b(FIG. 5). In the following, details of the pressing and the heating in the press-heating step are described.

The pressing of the module laminate10in the press-heating step is performed by providing a pressure difference between the upper vacuum region14aand the lower vacuum region14bof the laminating apparatus2so as to make the pressure of the upper vacuum region14ahigher. However, it is preferable that evacuation of the upper vacuum region14aand the lower vacuum region14bis initially performed, for the purpose of removing air bubbles existing inside the module laminate10.

By providing such a pressure difference, the diaphragm sheet15swells toward the lower vacuum region14bside. As a result, the diaphragm sheet15presses the module laminate10from the upper side of the mold release sheet21. Therefore, even if the resin layer5is softened in the press-heating step, occurrence of a misalignment between the members of the module laminate10can be suppressed.

Then, the pressure of the upper vacuum region14ais step by step made higher than the pressure of the lower vacuum region14b, so that the diaphragm sheet15swells toward the lower vacuum region14bside as shown inFIG. 5. The pressure difference between the upper vacuum region14aand the lower vacuum region14bmay be, for example, 300 to 500 torr.

At this time, the diaphragm sheet15applies pressure of about 0.4 kgf/cm2to 0.67 kgf/cm2to the laminate10. In this step, as shown inFIG. 6, the unevenness of the pressing member3is transferred to the back-surface sheet9, and thus protrusions having substantially the same shape as that of the pressing member3are formed on the back-surface sheet9and recesses having substantially the same shape as that of the pressing member3are formed in the resin layer5.

However, in the unevenness of the back-surface sheet9formed in this step, the protrusions protruding toward the light-transmitting substrate4side are larger in the regions above the intervals between the adjacent solar cell elements6than in the regions above the solar cell elements6. This is because resistance the back-surface sheet9receives from the resin layer5during the pressing is smaller in the regions above the intervals of the adjacent solar cell elements6than in the regions above the solar cell elements6.

Then, the heating of the module laminate10in the press-heating step is performed by the heater18aheating the heater board18. The resin forming the first resin layer5aand the second resin layer5bare softened by the heating, to be charged in the surrounding area of the solar cell elements6(FIG. 6). Then, the temperature is raised up to a temperature equal to or higher than the decomposing temperature of the contained cross-linking agent, so that cross-linking in the cross-linkable resin advances. Thereby, the molecular structure of the second resin layer5bbecomes a stable three-dimensional network having a cross-linking structure. The decomposing temperature of the cross-linking agent which is kneaded into the resin may be determined by, for example, a method of setting a reaction decomposition constant. The heating is performed until the shape of the resin forming the second resin layer5bis stabilized (a low fluid state), that is, until the second resin layer5bcan maintain the unevenness transferred to the back-surface sheet9.

For example, when the main component of the second resin layer5bis EVA, it is preferable that the heating is performed such that the degree of cross-linking of the EVA becomes 50% or more. By setting the degree of cross-linking in this manner, when the module laminate10is further heated in a subsequent step, a deformation caused by softening of the second resin layer5bcan be suppressed. Therefore, the unevenness once transferred to the back-surface sheet9by the pressing member3can be maintained. Although in the above-described press-heating step, the pressing and the heating are performed substantially at the same time, the heating may be performed after the pressing.

As described above, the module laminate10is heated while being pressed such that the protrusions or and recesses having the same sizes as those of the protrusions and recesses in the unevenness formed in the pressing surface of the pressing member3can be formed on the surfaces of the back-surface sheet9and the resin layer5. This can relieve wrinkles which have conventionally occurred in the back-surface sheet9during the integration of the module laminate10.

The degree of cross-linking (%) can be measured in the following procedure.

Firstly, approximately 0.3 to 5 g of the cross-linkable resin for each of the first resin layer5aand the second resin layer5bis cut out, and the mass thereof is weighed. Then, the weighed cross-linkable resin is immersed in approximately 100 ml of a solvent of xylene or toluene, and left at 100 to 120° C. for 20 to 30 hours. Then, the resin is taken out of the solvent, and dried in the air at 60 to 100° C. for 5 to 8 hours. Subsequently, the mass of each resin is weighed. The degree of cross-linking of each resin is calculated by the following expression.
Degree of cross-linking (%)=(Mass after immersed in the solvent/Mass before immersed in the solvent)×100

Next, a heating step after the press-heating step is described. The heating step is a step of heating the module laminate10under a pressure condition not allowing the unevenness of the pressing member3to be transferred to the back-surface sheet9and under a temperature condition equal to or higher than the cross-linking temperature of the resin forming the second resin layer5b. In this step, the pressing member3is removed from the module laminate3, and the module laminate10is taken out of the laminating apparatus2and placed in a heating furnace (not shown), so that the heating furnace performs the heating.

As the heating furnace, a furnace capable of performing a heating at a temperature equal to or higher than the cross-linking temperature of the cross-linkable resin forming the first resin layer5aand the second resin layer5bis used. For example, the heating furnace is preferably structured such that the module laminate10can be heated while being conveyed by a conveyor passing through the heating furnace.

The module laminate10is heated within the heating furnace until the cross-linkable resin forming the second resin layer5bis brought into a shape-fixed state (non-fluid state). Therefore, for example, when EVA is used as the main component of the second resin layer5b, the second resin layer5bis preferably heated until its degree of cross-linking becomes 90% or more.

Through the above-described heating step, a sufficient adhesive force between the back-surface sheet9and the second resin layer5bcan be obtained. Moreover, separation of the first resin layer5aand the second resin layer5hfrom the light-transmitting substrate4and the back-surface sheet9, which may be caused by aging, can be effectively suppressed.

If a plurality of module laminates10which have been press-heated by the laminating apparatus2are together subjected to the heating step in a single heating furnace, a production efficiency of the solar cell module100can be improved.

Then, a terminal box (not shown) whose casing is made of a polyphenylene ether resin or the like is fixed to the solar cell module100with an adhesive. Through this terminal box, power generated in the solar cell module100can be outputted to the outside. The solar cell module100is formed through the above-described steps.

As described above, in this embodiment, the integration of the module laminate10is performed while the unevenness of the pressing member3is being transferred to the back-surface sheet9. This allows a highly reliable integration of the module laminate10. Additionally, the difference in height in the unevenness of the back-surface sheet9is larger in the regions above the intervals between adjacent solar cell elements6than in the regions above the solar cell elements6. This can more efficiently relieve the stress caused by the difference among the respective members in the length of thermal expansion and contraction.

Second Embodiment

Next, a solar cell module200according to a second embodiment of the present invention is described.

FIG. 7is a cross-sectional view showing a configuration of the solar cell module200according to the second embodiment of the present invention. The configuration of the solar cell module200which is different from the configuration of the solar cell module100according to the first embodiment is described with reference toFIG. 7.

The solar cell module200mainly includes a light-transmitting substrate24, a string assembly12, a resin layer5, and a back-surface sheet9. The light-transmitting substrate24has a curved surface whose central portion protrudes relative to both end portions thereof in a direction opposite to the solar cell element6side. The string assembly12is provided over a back surface of the curved surface of the light-transmitting substrate24. The resin layer5is formed on a back surface of the light-transmitting substrate24so as to seal the string assembly12. The back-surface sheet9is formed on the resin layer5. Each of the resin layer5and the back-surface sheet9after formed as the solar cell module200has a curved shape corresponding to the shape of the light-transmitting substrate24. Similarly to the first embodiment, each of the back-surface sheet9and the resin layer5has unevenness. The light-transmitting substrate24as a whole is curved toward the side opposite to where the string assembly12is arranged.

FIG. 8is a cross-sectional view showing a configuration of a laminating apparatus22used in manufacturing the solar cell module200according to the second embodiment of the present invention. The laminating apparatus22has a heater board28formed in a shape that an upper surface thereof has a concave curve so as to follow the curved shape of the light-transmitting substrate24mounted thereon. The other parts of the structure are the same as those of the laminating apparatus2according to the first embodiment.

FIG. 9is a diagram showing a state after a module laminate20of this embodiment is press-heated. The module laminate20has a configuration in which the first resin layer5a, the string assembly12, the second resin layer5b, and the back-surface sheet9are laminated in the mentioned order on a back surface of a convex curved surface of the light-transmitting substrate4.

From the viewpoint of a change in the sheet thickness which is caused in integrating the members or the viewpoint of suppression of air remaining inside the laminate, it is preferable that the back-surface sheet9which is laminated in forming the module laminate20has a curved shape corresponding to the shape of the light-transmitting substrate24. On the other hand, from the viewpoint of, when the back-surface sheet9is put on the second resin layer Sb, obtaining a high degree of freedom in positioning between the back-surface sheet9and the light-transmitting substrate24having the curved shape, it is preferable that the back-surface sheet9has a flat plate shape.

It is preferable that a textile is used as the pressing member3because, when pressing, spaces between fibers of the textile are flexibly changed in accordance with the shape of the light-transmitting substrate4, to enable the back-surface sheet9to follow the shape of the light-transmitting substrate4with an enhanced accuracy.

In this embodiment, similarly to the first embodiment, the module laminate20is pressed and heated by using the laminating apparatus22. As a result, each of the resin layer5and the back-surface sheet9is given a curved shape corresponding to the shape of the light-transmitting substrate24having the curved surface, and additionally the unevenness of the pressing member3is transferred to the back-surface sheet9. Thus, the module laminate20which is curved as a whole is obtained. Even if the module laminate20is curved, wrinkles which have conventionally occurred in the back-surface sheet9can be relieved by performing the integration while transferring the unevenness.

As described above, in this embodiment, the light-transmitting substrate24and the members are integrated while the unevenness is being transferred to the back-surface sheet9. Thereby, even if the module laminate20is curved, the integration can be performed with a high reliability.

Third Embodiment

Next, a solar cell module300according to a third embodiment of the present invention is described.FIG. 10is a cross-sectional view showing a configuration of the solar cell module300according to the third embodiment of the present invention.

The solar cell module300mainly includes a light-transmitting substrate24, a string assembly12, a resin layer5, and a back-surface sheet9. The light-transmitting substrate24has a curved surface whose central portion protrudes relative to both end portions thereof in a direction opposite to the solar cell element6side. The string assembly12is provided over the back surface side of the curved surface. The resin layer5is formed on the light-transmitting substrate24so as to seal the string assembly12. The back-surface sheet9is formed on the resin layer5. Each of the resin layer5and the back-surface sheet9has a curved shape corresponding to the shape of the light-transmitting substrate24.

In this embodiment, similarly, the back-surface sheet9has a wave shape including a plurality of protrusions. However, this embodiment is different from the second embodiment, in that the interval between the adjacent protrusions of the back-surface sheet9and the height of the protrusion of the back-surface sheet9become larger with distance from a central portion of the curved surface of the light-transmitting substrate24. Such a shape is adopted in the back-surface sheet9, in order to effectively reduce wrinkles which tend to occur in end portions of the back-surface sheet9when the members are integrated, as described later. The resin layer5which is brought into contact with the back-surface sheet9is also given the same unevenness.

FIG. 11is a cross-sectional view showing a configuration of a laminating apparatus32used in manufacturing a solar cell300according to the third embodiment of the present invention. The laminating apparatus32has a pressing member33having a pressing surface on which a plurality of protrusions are formed. The pressing member33is structured such that the interval between the adjacent protrusions and the height of the protrusion become larger at a location closer to end portions than a central portion of the light-transmitting substrate4forming the module laminate30to be pressed. The other parts of the structure are the same as those of the laminating apparatus22according to the second embodiment.

FIG. 12is a diagram showing a state after the module laminate30of this embodiment is press-heated. By pressing and heating the module laminate30by using the above-described laminating apparatus32, protrusions and recesses which are substantially the same as those of the unevenness of the pressing member33are formed in the back-surface sheet9and the resin layer5.

This can efficiently relieve wrinkles which conventionally tend to occur in end portions of the back-surface sheet9.

In the above-described embodiment, a method in which the module laminate10is removed from the pressing member3of the laminating apparatus2, and heated in the heating furnace is described. However, not only this but a method in which the module laminate10is heated in the heating furnace while the pressing member3is attached thereto may be adopted.

For example, it may be acceptable that a process in the heating furnace is performed in a state where pressure is applied to the module laminate10by placing a weight on the pressing member3disposed on the back-surface sheet9. Any weight may be used as long as it is a member having a weight not relieving the unevenness transferred to the back-surface sheet9by the pressing member3. It is preferable to use a glass plate or aluminium.

In this case, the press-heating step using the laminating apparatus2is performed until air bubbles existing within the module laminate10are sufficiently removed and the first resin layer5aand the second resin layer5bare charged throughout the surrounding area of the solar cell element6. Then, the module laminate10with the weight placed on the pressing member is taken out of the laminating apparatus2and put into the heating furnace.

In this embodiment, the unevenness including a plurality of protrusions transferred to the back-surface sheet9is maintained by the weight. Therefore, the degree of cross-linking of the cross-linkable resin can be set low (for example, 10% or less) in the press-heating step, which can shorten a time required for the press-heating step. Additionally, the heating furnace is more excellent in productivity than the laminating apparatus2is, and many solar cell modules can be put therein. This can increase yield of the solar cell module, even when the same manufacturing machine as in the above-described embodiments is used.