Patent Publication Number: US-2015083188-A1

Title: Solar cell module and solar cell module manufacturing method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation under 35 U.S U.S.C. §120 of PCT/JP2012/066771, filed Jun. 29, 2012, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a solar cell module and a method of manufacturing a solar cell module. 
     BACKGROUND ART 
     As shown in  FIG. 10 , a solar cell module  100  has a structure in which collecting electrodes  12  provided for a plurality of solar battery cells  10  are connected to each other by connection members  14 . The connection member  14  is adhered to be in electrical conduct with the collecting electrode  12  by a conductive adhesive film in which conductive particles are dispersed. 
     During thermocompression of the connection member  14 , a heating process of about 200° C. is employed. Therefore, when the solar battery cell  10  is cooled after the thermocompression, a contraction force due to thermal contraction of the connection member  14  would be applied on a light receiving surface and a back surface of the solar battery cell  10 . 
     Meanwhile, on the side of the back surface of the solar battery cell  10 , the incidence of light does not need to be considered. Thus, in many cases, a placement area of the collecting electrode  12  is set to be larger compared to the side of the light receiving surface, and the adhesion area between the connection member  14  and the collecting electrode  12  is also larger on the back surface side than the light receiving surface side. In addition, the contraction force applied on the light receiving surface and the back surface of the solar battery cell  10  depends on an adhesion force; that is, an adhesion area, between the connection member  14  and the collecting electrode  12 . Therefore, when the amounts of adhesives between the connection member  14  and the collecting electrode  12  are the same on the light receiving surface side and the back surface side, the contraction force applied to the solar battery cell  10  would be greater for the back surface side having the larger adhesion area, and, as shown in  FIG. 11 , curling and cracks may occur in the solar battery cell  10 . 
     Moreover, the curling and the cracks may occur in the solar battery cell  10  from the difference itself in the placement areas of the collecting electrodes  12  provided over the light receiving surface and the back surface of the solar battery cell  10 . Specifically, a stronger contraction force would be applied on a side having a larger placement area of the collecting electrode  12  on the light receiving surface or the back surface, and the curling and the cracks may be caused in the solar battery cell  10 . In the future, as the thickness of the solar battery cell  10  is reduced, this problem will become more and more significant. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, there is provided a solar cell module comprising: a plurality of solar cells; and a connection member that connects the plurality of solar cells, wherein an area of an adhesive layer that adheres the connection member over a light receiving surface of the solar cell is larger than an area of an adhesive layer that adheres the connection member over a back surface of the solar cell. 
     According to another aspect of the present invention, there is provided a method of manufacturing a solar cell module, comprising: a first step in which a connection member is adhered over a light receiving surface of a solar cell with an adhesive layer therebetween; and a second step in which a connection member is adhered over a back surface of the solar cell with an adhesive layer therebetween such that an area of the adhesive layer that adheres the connection member over the light receiving surface of the solar cell is larger than an area of the adhesive layer that adheres the connection member over the back surface of the solar cell. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a plan view showing a light receiving surface of a solar cell module according to a preferred embodiment of the present invention. 
         FIG. 2  is a plan view showing a back surface of a solar cell module according to the preferred embodiment of the present invention. 
         FIG. 3  is across sectional diagram showing a solar cell module according to the preferred embodiment of the present invention. 
         FIG. 4  is a plan view showing an adhesive layer over a light receiving surface in the preferred embodiment of the present invention. 
         FIG. 5  is a plan view showing an adhesive layer over a back surface in the preferred embodiment of the present invention. 
         FIG. 6  is a diagram for explaining an operation of the solar cell module according to the preferred embodiment of the present invention. 
         FIG. 7  is a cross sectional diagram showing a joining member over a surface of which an unevenness is provided. 
         FIG. 8  is a plan view showing an adhesive layer according to the preferred embodiment of the present invention. 
         FIG. 9  is a diagram for explaining an operation of a solar cell module according to the preferred embodiment of the present invention. 
         FIG. 10  is a plan view showing a solar cell module of related art. 
         FIG. 11  is a diagram for explaining curling which occurs in a solar cell module of related art. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As shown in plan views of  FIGS. 1 and 2  and a cross sectional diagram. of  FIG. 3 , a solar cell module  200  according to a preferred embodiment of the present invention includes a solar battery cell  202 , a connection member  204 , and an adhesive layer  206 .  FIG. 1  is a plan view of the solar cell module  200  viewed from the light receiving surface side, and  FIG. 2  is a plan view of the solar cell module  200  viewed from the back surface side.  FIG. 3  is a cross sectional diagram along an A-A line in  FIG. 1 . 
     A “light receiving surface” refers to a primary surface of the solar battery cell  202 , and is a surface through which the light from the outside primarily enters the solar cell. For example, 50%˜100% of the light entering the solar battery cell  202  enters from the side of the light receiving surface. A “back surface” refers to another primary surface of the solar battery cell  202 , and is a surface on a side opposite from the light receiving surface. The solar battery cell  202  includes a photoelectric conversion unit  20   a  that receives light such as solar light and produces carriers (electrons and holes), a first electrode  20   b  provided over the light receiving surface of the photoelectric conversion unit  20   a,  and a second electrode  20   c  provided over the back surface of the photoelectric conversion unit  20   a.  As shown in  FIGS. 1 and 2 , the first electrode  20   b  and the second electrode  20   c  are collecting electrodes having fingers provided in a comb shape to intersect a direction of extension of the connection member  204 , and bus bars connecting the fingers. The finger is a narrow line-shaped electrode that collects electric power from the photoelectric conversion unit  20   a.  The bus bars are electrodes that connect a plurality of the fingers, and are placed in parallel to each other with a predetermined gap therebetween and in a manner to be covered by the connection member  204 . The fingers and bus bars are formed, for example, by screen printing in a desired pattern over a transparent conductive layer a conductive paste in which a conductive filler such as silver (Ag) is dispersed in a binder resin. In the solar battery cell  202 , the carriers produced at the photoelectric conversion unit  20   a  are collected by the first electrode  20   b  and the second electrode  20   c.    
     In the solar battery cell  202 , because the amount of incidence of light is lower on the back surface than on the light receiving surface, the second electrode  20   c  over the back surface is formed having a larger area than the first electrode  20   b  over the light receiving surface. For example, a greater number of fingers are provided in the first electrode  20   b  than in the second electrode  20   c.  Alternatively, when there is no incidence of light from the back surface side of the solar battery cell  202 , a metal film such as a silver (Ag) thin film may be formed over substantially the entire surface of the back surface of the photoelectric conversion unit  20   a,  to form the second electrode  20   c.    
     The photoelectric conversion unit  20   a  has a substrate made of a semiconductor material such as, for example, crystalline silicon, gallium arsenide (GaAs), indium phosphide (InP), or the like. A structure of the photoelectric conversion unit  20   a  is not particularly limited, and in the present embodiment, the photoelectric conversion unit  20   a  has a structure having a hetero junction of an n-type monocrystalline silicon substrate and amorphous silicon. In the photoelectric conversion unit  20   a,  for example, over the light receiving surface of the n-type monocrystalline silicon substrate, an i-type amorphous silicon layer, a p-type amorphous silicon layer doped with boron (B) or the like, and a transparent conductive layer made of a transparent conductive oxide such as indium oxide, are layered in that order. In addition, over the back surface of the substrate, an i-type amorphous silicon layer, an n-type amorphous silicon layer doped with phosphorus (P) or the like, and a transparent conductive layer are layered in that order. 
     In the solar cell module  200 , adjacent solar battery cells  202  are connected by the connection member  204 . As the connection member  204 , for example, a metal foil of copper or the like may be employed. The connection member  204  connects the first electrode  20   b  of a solar battery cell  202  and a second electrode  20   c  of an adjacent solar battery cell  202 . The connection member  204  is adhered to, for example, a bus bar and a finger of the first electrode  20   b  of one solar battery cell  202  and a bus bar and a finger of the second electrode  20   c  of the other solar battery cell  202 , by the adhesive layer  206 . 
     The adhesive layer  206  may be, for example, a conductive adhesion film or a conductive adhesion paste in which conductive particles are dispersed in a thermosetting resin material having an adhering characteristic such as an epoxy resin, an acrylic resin, a urethane resin, or the like. The conductive adhesion film may be an anisotropic conductive adhesive having a high conductivity in an in-plane direction and a low conductivity in a thickness direction of the solar battery cell  202 . Alternatively, there may be employed a non-conductive adhesive paste which does not contain the conductive particles in the thermosetting resin material having an adhering characteristic such as the epoxy resin, the acrylic resin, and the urethane resin. 
     The connection member  204  has a bent portion in which a step is provided corresponding to the thickness of the solar battery cell  202 . The bent portion is provided to form a structural clearance corresponding to the thickness of the solar battery cell  202  for connecting the first electrode  20   b  and the second electrode  20   c  to place the adjacent solar battery cells  202  on the same plane. 
     The solar cell module  200  maybe sealed by a protection member (not shown) for protecting the light receiving surface and the back surface of the solar battery cell  202 . For the protection member, a member having a light transmitting characteristic such as, for example, a glass plate, a resin plate, a resin film, or the like maybe employed. The protection member provided on the side of the light receiving surface of the solar battery cell  202  is preferably a transparent member that transmits light of a wavelength band used for the photoelectric conversion at the solar battery cell  202 . When there is no incidence of light from the back surface side of the solar battery cell  202 , the protection member provided over the back surface side may be a non-transparent plate or film. In this case, as the protection member, for example, a layered film such as a resin film having therein an aluminum foil or the like, may be employed. The protection members are adhered to the light receiving surface and the back surface of the solar battery cell  202  using fillers. 
     In the solar cell module  200  in the present embodiment, the area of the adhesive layer  206  for adhering the connection member  204  is set different between the light receiving surface and the back surface. Specifically, the area of the adhesive layer  206  of the surface having the smaller placement area between the first electrode  20   b  of the light receiving surface and the second electrode  20   c  of the back surface is set to be larger. In other words, when the placement area of the first electrode  20   b  over the light receiving surface is set smaller than the placement area of the second electrode  20   c  over the back surface, the area of the adhesive layer  206  used for adhering the connection member  204  over the light receiving surface is set larger than the area of the adhesive layer  206  used for adhering the connection member  204  over the back surface. 
     For example, when the connection member  204  is adhered on the light receiving surface side, as shown by hatching in  FIG. 4 , the adhesive layer  206  is applied over the entire surface of the connection member  204 . On the other hand, when the connection member  204  is adhered on the back surface side, as shown by hatching in  FIG. 5 , an application width of the adhesive layer  206  may be narrowed, and the adhesive layer  206  may be provided on only a part of the connection member  204 . 
     In this process, the areas of the adhesive layers  206  are set such that the contraction force due to the connection member  204  adhered by the adhesion layer  206  is approximately equal between the light receiving surface and the back surface. For example, the areas of the adhesive layers  206  are preferably set such that an adhesion area between the connection member  204  and the first electrode  20   b  over the light receiving surface is approximately equal to an adhesion area between the connection member  204  and the second electrode  20   c  over the back surface. In addition, the areas of the adhesive layers  206  are preferably set such that the connection members  204  do not peel off from the solar battery cell  202 . 
     Here, the area of the adhesive layer and the placement area of the electrode refer to the areas occupied by the adhesive layer and the electrode when the solar battery cell  202  is viewed in a plan view from the light receiving surface side or the back surface side as in the plan views of  FIGS. 1 ,  2 ,  4 , and  5 . 
     The contraction forces applied to the light receiving surface and the back surface of the solar battery cell  202  depend on the adhesion forces between the connection member  204  and the first electrode  20   b  and the second electrode  20   c;  that is, adhesion areas between the connection member  204  and the first electrode  20   b  and the second electrode  20   c,  and the area of the adhesive layer. In the present embodiment, the adhesion area between the connection member  204  and the first electrode  20   b  is set smaller than the adhesion area between the connection member  204  and the second electrode  20   c,  and the area of the adhesive layer between the connection member  204  and the first electrode  20   b  is set larger than the area of the adhesive layer between the connection member  204  and the second electrode  20   c.  Therefore, as shown by a side view of the solar battery cell  202  of  FIG. 6 , the contraction forces applied to the light receiving surface and the back surface of the solar battery cell  202  become more uniform, and, consequently, the curling and the cracks of the solar battery cell  202  can be inhibited. 
     Alternatively, as shown in  FIG. 7 , an unevenness  204   a  may be provided over one surface of the connection member  204 . By providing such unevenness  204   a  over one surface of the connection member  204 , it becomes possible to achieve a diffusion reflection of the light entering the unevenness  204   a,  a further reflection by a glass member or the like covering the surface of the connection member  204 , and to then introduce the light into the solar battery cell  202 . Therefore, the usage efficiency of light in the solar cell module  200  can be improved. The unevenness  204   a  is preferably provided to be oriented toward the light receiving surface. 
     In this configuration, even when the unevenness  204   a  is provided over one surface of the connection member  204 , the areas of the adhesive layers  206  may be set such that the contraction forces of the light receiving surface and the back surface by the connection member  204  to be adhered by the adhesive layer  206  are approximately equal to each other. In this manner, the contraction force due to the adhesion is balanced between the light receiving surface and the back surface, and the curling and the cracks of the solar battery cell  202  can be inhibited. 
     As the contraction force differs between a center part and a part near the end of the solar battery cell  202 , alternatively, the area of the adhesive layer  206  per unit area of the solar battery cell  202  may be set to vary along the longitudinal direction of the adhesive layer  206 . For example, a width of the adhesive layer  206  is set to vary along the longitudinal direction of the connection member  204 . As shown in the plan view of the connection member  204  of  FIG. 8 , a region having a width W 2  of the adhesive layer  206  narrower than a width W 1  near the center of the solar battery cell  202  may be provided near the end. By adjusting the area of the adhesive layer  206  in this manner, the contraction force applied to the solar battery cell  202  can be finely adjusted, and the contraction forces applied to the light receiving surface and the back surface of the solar battery cell  202  can be made more uniform. Therefore, a more significant advantage of inhibiting the curling and the cracks of the solar battery cell  202  can be achieved. 
     Alternatively, the curling and the cracks of the solar battery cell  202  caused by a difference in the placement areas of the first electrode  20   b  and the second electrode  20   c  provided over the light receiving surface and the back surface of the solar battery cell  202  can be reduced. For example, when the placement area of the second electrode  20   c  over the back surface is larger than the placement area of the first electrode  20   b  over the light receiving surface, as shown in  FIG. 9(   a ), the solar battery cell  202  may curl in a convex manner in the light receiving surface side. However, by adjusting the area of the adhesive layer  206  for adhering the connection member  204 , as shown in  FIG. 9(   b ), the curling of the solar battery cell  202  can be actively resolved. In particular, as the thickness of the solar battery cell  10  is reduced, the advantage of the prevention of the curling becomes more and more significant. 
     As described, according to the solar cell module  200  of the present embodiment, generation of curling, cracks, or the like of the solar battery cell  202  can be inhibited and reliability of the solar cell module  200  can be improved.