Patent Publication Number: US-2015083187-A1

Title: Solar cell module and solar cell module manufacturing method

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation under 35 U.S.C §120 of PCT/JP2012/066772, filed on Jun. 29, 2012, which is incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to a solar cell module and a solar cell module manufacturing method. 
     BACKGROUND ART 
     A solar cell module  100  has, as shown in  FIG. 7 , a structure in which collecting electrodes  12  provided in a plurality of solar cells  10  are connected to each other by means of connecting members  14 . The connecting members  14  are conductively adhered to the collecting electrodes  12  by means of a conductive adhesive film in which conductive particles are dispersed (see Patent Document 1). 
     CITATION LIST 
     Patent Document 
     Patent Document 1: JP 2011-108985 A 
     If the adhesive force between the solar cell  10  and the connecting member  14  decreases, there is a risk that the connecting member  14  peels off. Meanwhile, if too much adhesive is used to enhance the adhesive force, the adhesive protrudes from the connecting member  14 , and the protruding adhesive shades the solar cell  10 , which may cause degradation of the conversion efficiency. 
     SUMMARY 
     According to one embodiment of the present invention, there is provided a solar cell module having a plurality of solar cells, and a connecting member which connects between the plurality of solar cells via an adhesive layer, and the solar cell module has an adhesion portion having a contact length between the adhesive layer and the connecting member, the contact length being longer at an edge portion than at a central portion of the solar cell along the longitudinal direction of the connecting member. 
     According to another embodiment of the present invention, there is provided a method of manufacturing a solar cell module including a first step of applying an adhesive onto a plurality of solar cells, the adhesive becoming an adhesive layer, and a second step of connecting between the plurality of solar cells by means of a connecting member via the adhesive layer, and, in this method, there is provided an adhesion portion having a contact length between the adhesive layer and the connecting member, the contact length being longer at an edge portion than at a central portion of the solar cell along the longitudinal direction of the connecting member. 
     ADVANTAGEOUS EFFECT OF INVENTION 
     With the present invention, it is possible to strengthen contact between the solar cell and the connecting member in the solar cell module, and reduce shading loss. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a plan view illustrating a solar cell module in an embodiment of the present invention. 
         FIG. 2  shows a cross-sectional view illustrating the solar cell module in the embodiment of the present invention. 
         FIG. 3  shows a cross-sectional view illustrating the solar cell module in the embodiment of the present invention. 
         FIG. 4  shows a cross-sectional view illustrating a joint member having a surface on which uneven shape is provided in the embodiment of the present invention. 
         FIG. 5  shows a plan view illustrating an adhesive layer in the embodiment of the present invention. 
         FIG. 6  shows a cross-sectional view illustrating the solar cell module in the embodiment of the present invention. 
         FIG. 7  shows a plan view of a conventional solar cell module. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     A solar cell module  200  according to an embodiment of the present invention is, as shown in the plan view in  FIG. 1  and in the cross-sectional views in  FIG. 2  and  FIG. 3 , configured to include solar cells  202 , connecting members  204 , and adhesive layers  206 .  FIG. 1  shows the plan view of the solar cell module  200  as seen from the light receiving surface side.  FIG. 2  shows the cross-sectional view, taken along line A-A in  FIG. 1 , and  FIG. 3  shows the cross-sectional view, taken along line B-B in  FIG. 1 . 
     The “light receiving surface” is one of the main surfaces of the solar cell  202  and is a surface which receives light mainly entering from outside. For example, 50% to 100% of incident light to the solar cell  202  enters from the light receiving surface side. There is a “back surface” which is one of the main surfaces of the solar cell  202 , and is a surface on the opposite side to the light receiving surface. 
     The solar cell  202  includes a photoelectric conversion unit  20   a  which generates carriers (electrons and holes) by receiving light such as solar light, a first electrode  20   b  provided on the light receiving surface of the photoelectric conversion unit  20   a,  and a second electrode  20   c  provided on the back surface of the photoelectric conversion unit  20   a.  The first electrode  20   b  is, as shown in  FIG. 1 , a collecting electrode which has fingers arranged in a pectinate shape so as to intersect the extending direction of the connecting member  204 , and bus bars for connecting the fingers. The fingers are thin line electrodes for collecting electrical power from the photoelectric conversion unit  20   a.  The bus bars are electrodes for connecting the plurality of fingers, and are arranged in parallel to each other with a predetermined space therebetween so as to be covered by the connecting members  204 . The fingers and the bus bars are formed, for example, by screen printing with a conductive paste. The conductive paste comprises conductive fillers such as silver (Ag) which are dispersed in a binder resin, and is provided in a desired pattern on a transparent conductive layer. The second electrode  20   c  is provided on the back surface side of the photoelectric conversion unit  20   a  in the same manner as the first electrode  20   b.  In the solar cell  202 , the carriers generated by the photoelectric conversion unit  20   a  are collected by the first electrode  20   b  and the second electrode  20   c.    
     Because, in the solar cell  202 , light entering the back surface is less than that entering the light receiving surface, the second electrode  20   c  on the back surface may have a larger area than the first electrode  20   b  on the light receiving surface. For example, the second electrode  20   c  may have a larger number of fingers than the first electrode  20   b.  Further, if there is no light entering from the back surface side of the solar cell  202 , a metal layer made of, for example, silver (Ag) may be formed on approximately the entire surface of the back surface of the photoelectric conversion unit  20   a  and may be used as 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), or indium phosphide (InP). Although the structure of the photoelectric conversion unit  20   a  is not particularly limited, in the present embodiment, the description will be provided on the assumption that the structure has a heterojunction between an n-type monocrystal silicon substrate and amorphous silicon. In the photoelectric conversion unit  20   a,  for example, an i-type amorphous silicon, a p-type amorphous silicon in which, for example, boron (B) is doped, and a transparent conductive layer made of transparent conductive oxide, such as indium oxide, are layered in this order. Further, on the back surface of the substrate, an i-type amorphous silicon layer, an n-type amorphous silicon layer in which, for example, phosphorus (P) is doped, and a transparent conductive layer are layered in this order. 
     In the solar cell module  200 , the adjacent solar cells  202  are connected to each other by the conductive connecting members  204 . A metallic foil made of, for example, copper can be used as the connecting member  204 . The connecting member  204  connects the first electrode  20   b  of the solar cell  202  with the second electrode  20   c  of the adjacent solar cell  202 . The connecting members  204  are adhered to the bus bars and the fingers of the first electrode  20   b  of one solar cell  202  and to the bus bars and the fingers of the second electrode  20   c  of another solar cell  202 , using an adhesive layer  206 . 
     For example, a conductive adhesive film or a conductive adhesive paste in which conductive particles are dispersed in an adhesive thermosetting resin material, such as epoxy resin, acrylic resin, or urethane resin, can be used as the adhesive layer  206 . The conductive adhesive film may be an anisotropic conductive adhesive which has high conductivity in the in-plane direction of the solar cell  202  and lower conductivity in the film thickness direction. Further, a nonconductive paste in which no conductive particle is included in an adhesive thermosetting resin material, such as epoxy resin, acrylic resin, or urethane resin, may also be used. In this case, as shown in  FIG. 4 , one of the first electrode  20   b,  the second electrode  20   c,  and the connecting member  204  is provided with uneven shape  204   a  so that the first electrode  20   b  and the second electrode  20   c  are electrically connected to the connecting member  204  via the uneven shape  204   a.    
     The connecting member  204  has a bent portion on which a step of the thickness of the solar cell  202  is provided. The bent portion is provided such that a structural clearance of the thickness of the solar cell  202  is formed, in order to connect the first electrode  20   b  to the second electrode  20   c  so as to arrange the adjacent solar cells  202  within the same plane. 
     The solar cell module  200  may be sealed by a protection component (not shown), in order to protect the light receiving surface and the back surface of the solar cell  202 . For example, a component having translucence, such as a glass plate, a resin plate, or a resin film, can be used as the protection component. Preferably, the protection component provided on the light receiving surface side of the solar cell  202  is a transparent component which transmits light of a wavelength bandwidth used for photoelectric conversion in the solar cell  202 . If there is no incident light from the back surface side of the solar cell  202 , an opaque plate body or film may be used as the protection component on the back surface side. In this case, a laminated film, such as a resin film having, for example, aluminum foil therein, can be used as the protection component. The protection component is adhered to each of the light receiving surface and the back surface of the solar cell  202  by means of fillers. 
     In the solar cell module  200  of the present embodiment, the contact lengths between the adhesive layer  206  and the connecting member  204  differ between the edge portion and the central portion of the solar cell  202  along the longitudinal direction of the connecting member  204 . More specifically, as shown in  FIG. 2  and  FIG. 3 , the solar cell module  200  has an adhesion portion which has a longer contact length between the adhesive layer  206  and the connecting member  204  at the edge portion of the solar cell  202  than at the central portion along the longitudinal direction of the connecting member  204 . 
     Here, the contact length between the adhesive layer  206  and the connecting member  204  means, as shown in  FIG. 2  and  FIG. 3 , a length over which the adhesive layer  206  and the connecting member  204  contact each other in a cross section which is vertical to the longitudinal direction of the connecting member  204 . In addition, the edge portion and the central portion of the solar cell  202  indicate a relative positional relation between them, and the edge portion means an area that is closer to an edge of the solar cell  202  than is the central portion. More specifically, in the present embodiment, when a certain region of the connecting member  204  is focused on, the contact length between the connecting member  204  and the adhesive layer  206  in a region which is closer to the edge of the solar cell  202  than the focused region, is longer than that of the focused region. 
     For example, as shown in  FIG. 5 , the adhesive layer  206  may be applied along the longitudinal direction of the connecting member  204  (shown by the dotted line) so that the width of the adhesive layer  206  becomes larger at the edge portion and smaller at the central portion of the solar cell  202 . At this time, it is preferable to provide the adhesion portion having the longer contact length between the adhesive layer  206  and the connecting member  204  than at the central portion of the solar cell  202 , not only at the edge portion of the connecting member  204  but also at the edge portion of the solar cell  202  on the side from which the connecting member  204  is pulled out toward the adjacent solar cell  202 . 
     To change the contact length between the connecting member  204  and the adhesive layer  206  along the longitudinal direction of the connecting member  204 , the application quantity of the adhesive, which becomes the adhesive layer  206  along the longitudinal direction of the connecting member  204 , may be changed upon application of the adhesive, which becomes the adhesive layer  206 . For example, a larger amount of the adhesive may be applied to the edge portion of the solar cell  202  than at the central portion along the longitudinal direction of the connecting member  204 , and then, the connecting member  204  may be crimped. Methods that can be used to change the application amount of the adhesive include changing the moving velocity of a dispenser along the longitudinal direction of the connecting member  204 , and changing the ejection pressure of the adhesive from the dispenser along the longitudinal direction of the connecting member  204 . 
     Because, in general, a region which is close to the edge of the solar cell  202  is a region at which adhesion between the connecting member  204  and the first electrode  20   b  tends to separate, by making the contact length at the edge portion of the solar cell  202  longer than that at the central portion, it is possible to effectively suppress peeling off. In addition, the same can be said about the relationship between the connecting member  204  and the second electrode  20   c.  Meanwhile, because the contact length is shorter at the central portion than at the edge portion, it is possible to suppress, at the central portion, protrusion of the adhesive layer  206  from the connecting member  204 , and control shading loss caused by the adhesive layer  206 . 
     Preferably, as shown in the cross-sectional view in  FIG. 6 , a fillet  22  of the adhesive layer  206  is formed at the contact portion between the connecting member  204  and the first electrode  20   b  at the edge of the solar cell  202 . The fillet  22  means a portion at which a portion of the adhesive layer  206  contacts the side surface of the connecting member  204 . By providing the fillet  22 , the contact between the connecting member  204  and the first electrode  20   b  is strengthened at the edge portion of the solar cell  202 , and the effect of suppressing peeling off of the connecting member  204  becomes remarkable. The same can be said about the relationship between the connecting member  204  and the second electrode  20   c.    
     REFERENCE SIGNS LIST 
       10  SOLAR CELL,  10  COLLECTING ELECTRODE,  14  CONNECTING MEMBER,  20   a  PHOTOELECTRIC CONVERSION UNIT,  20   b  FIRST ELECTRODE,  20   c  SECOND ELECTRODE,  22  FILLET,  100 ,  200  SOLAR CELL MODULE,  202  SOLAR CELL,  204  CONNECTING MEMBER,  206  ADHESIVE LAYER.