Patent Publication Number: US-2011048492-A1

Title: Solar cell and solar cell module

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application of the invention titled “Solar Cell and Solar Cell Module” is based upon and claims the benefit of priority under 35 USC 119 from prior Japanese Patent Application No. 2009-200687, filed on Aug. 31, 2009; the entire contents of which are incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a solar cell and a solar cell module. 
     2. Description of Related Art 
     A solar cell system having solar cells is expected to be a new energy conversion system that converts light from the sun into electricity. In recent years, active use of solar cell systems has been increasing as a general household power supply and a large-scale power generation plant. 
     Currently, under the situation described above, research and development for cost reduction of solar cell systems are actively in progress in order to further spread their use. 
       FIG. 14A  is a perspective view of a solar cell in a solar cell module according to a related art,  FIG. 14B  is a sectional view of the solar cell,  FIG. 15  is a sectional view of a part of the solar cell module, illustrating the connection between the solar cells. 
     As shown in  FIGS. 14A and 14B , solar cell  100  includes semiconductor substrate  101  having a PN junction. Provided on the front surface of semiconductor substrate  101  are: antireflective film  102 ; and front electrode  103  composed of finger collecting electrodes  103   a  and bus bar electrodes  103   b . Provided on the rear surface of semiconductor substrate  101  is: rear electrode  104  composed of metal-film collecting electrode  104   a  and bus bar electrodes  104   b.    
     As shown in  FIG. 15 , in the solar cell module, bus bar electrodes  103   b  of front electrode  103  of one of adjacent solar cells  100  are connected to bus bar electrodes  104   b  of rear electrode  104  of the other of the adjacent solar cells  100  with conductive connection member  105  covered with a solder, so that plural solar cells  100  are electrically connected in series or parallel. 
     The electrically-connected plural solar cells are provided in a filling material filled between an unillustrated front cover made of a light transmissive member and an unillustrated rear cover with a frame supporting the outer edges of the front cover and the rear cover. 
     In the related art, conductive connection member  105  is generally connected to front electrodes  103  or rear electrodes  104  by melting and solidification of the solder of conductive connection member  105 . In such a connecting process wherein the solder is melted with heat, a difference in the thermal expansion coefficients between semiconductor substrate  101  of solar cell  100  and conductive connection member  105  generates stress in solar cell  100 . This may cause a crack in the solar cell (the substrate) and lower the yield of the solar cell. 
     Meanwhile, as a connecting method for connecting conductive connection member  105  to front electrode  103  of solar cell  100  or rear electrode  104  of solar cell  100 , there has been suggested a connecting method using a solder and a resin adhesive or a connecting method using a conductive resin adhesive (for example, see Japanese Patent Application Laid-Open No. S58-71667). 
     Such connecting methods using the resin adhesives do not require excessive heat and thus reduce cracks in the solar cell caused by heat. 
     SUMMARY OF THE INVENTION 
     In cases where such a resin adhesive is used for connecting conductive connection member  105  to front electrode  103  of one of adjacent solar cells  100  and/or rear electrode  104  of the other of the adjacent solar cells  100 , conductive connection member  105  may be mechanically connected to front electrode  103  and/or rear electrode  104  without melting and solidification of the solder. Therefore, it is possible to narrow the width of bus bar electrodes  103   b  of front electrode  103  compared to the related art or it is possible to eliminate bus bar electrodes  103   b.    
     In this configuration, stress in solar cell  100  is more concentrated at a contact area between front electrode  103  and conductive connection member  105  in the connecting process, compared to the related art. This may increase the occurrence of cracks in the solar cell and thus lower the yield of the solar cell. 
     Further, the solar cell may crack due to the stress in the solar cell even though the contact area between front electrode  103  and conductive connection member  105  is designed to be large. 
     An aspect of the invention is to provide a solar cell and a solar cell module capable of improving the yield. 
     A first aspect of the invention is a solar cell including: a photoelectric conversion body including a first main surface and a second main surface opposed to the first main surface; a first electrode provided on the first main surface; a second electrode provided on the second main surface; a first conductive connection member connected with the first electrode for connecting the solar cell and another solar cell, wherein the first conductive connection member includes a conductive soft layer at an area facing the first electrode, and the first electrode includes a conductive soft layer at an area facing the first conductive connection member; and a first resin adhesive bonding the first conductive connection member to the first electrode in such a manner that the conductive soft layer of the first electrode and the conductive soft layer of the first conductive connection member abut to each other. 
     According to the first aspect, in a step of fixing the first conductive connection member on the first electrode, the conductive soft layer of the first electrode and the conductive soft layer of the first conductive connection member function as cushions to reduce the occurrence of cracks in the solar cell. This improves the production yield. 
     In the first aspect, the conductive soft layer of the first electrode and the conductive soft layer of the first conductive connection member may be in contact with each other with at least one of them being deformed. This structure increases the contact area and thus improves the electrical connection and the mechanical connection between the first electrode and the first conductive connection member. 
     In the first aspect, the first electrode may comprise plural narrow line electrodes. Also, the plural narrow line electrodes may be connected to each other with another narrow line electrode. 
     The first aspect may further include: a second conductive connection member connected with the second electrode for connecting the solar cell to another solar cell, wherein the second conductive connection member includes a conductive soft layer at an area facing the second electrode, and the second electrode includes a conductive soft layer at an area facing the second conductive connection member; and a second resin adhesive bonding the second conductive connection member to the second electrode in such a manner that the conductive soft layer of the second electrode and the conductive soft layer of the second conductive connection member abut to each other. 
     With this structure, the conductive soft layer of the second electrode and the conductive soft layer of the second conductive connection member function as cushions. Accordingly, the cushion effects are obtained on both of the first main surface and the second main surface in the step(s) of fixing the conductive connection member(s) on the first electrode and the second electrode. This reduces the occurrence of cracks of the first main surface and the second main surface of the solar cell and thus further improves the production yield. 
     In the first aspect, a curing temperature of the adhesive may be lower than the melting point of the conductive soft layer. 
     With this configuration, the step(s) of fixing the conductive connection member(s) on the first electrode and/or the second electrode can be performed without the conductive soft layer(s) being melted. Therefore, the conductive soft layer(s) functions as a cushion(s) adequately and a problem that the conductive soft layer(s) melts and flows to undesired portion(s) does not occur. 
     The resin adhesive may be a conductive adhesive containing conductive particles such as Ni, Ag, or the like. The resin adhesive may contain nonconductive particles (nonconductive materials). The resin adhesive may contain both conductive particles and nonconductive particles, or may contain neither conductive particles nor nonconductive particles. 
     It is preferable that the adhesive is hardening resin such as epoxy-type resin. 
     It is preferable that the conductive soft layer of the first electrode is made of a material softer than the main body of the first electrode. 
     It is preferable that the conductive soft layer of the second electrode is made of a material softer than the main body of the second electrode. 
     It is preferable that the conductive soft layers of the conductive connection members are made of materials softer than the conductive connection members, respectively. 
     It is preferable that the conductive soft layer of the first electrode, the conductive soft layer of the second electrode, and the conductive soft layers of the conductive connection members are softer than the main body of the first electrode, the main body of the second electrode, and the main bodies of the conductive connection members, respectively. 
     The conductive soft layer may be made of solder. 
     The conductive soft layer of the first electrode, the conductive soft layer of the second electrode, the conductive soft layer of the first conductive connection member, and the conductive soft layer of the second conductive connection member may be made of different materials. It is preferable that all the conductive soft layers are made of the same material. With this configuration, conditions such as temperature conditions or the like in the fixing step using the resin adhesive can be readily set, thereby facilitating the manufacture of the solar cell. 
     In the first aspect, at least one of the first electrode and the second electrode may extend into the conductive soft layer of the corresponding conductive connection member. 
     In this configuration, the first or second conductive connection member is sufficiently fixed, and this improves the mechanical connection as well as the electrical connection. 
     In the first aspect, the conductive soft layer of the first electrode and the conductive soft layer of the first conductive connection member may be in contact with each other with at least one of them being deformed. 
     This configuration increases the contact area and thus improves the electrical connection and the mechanical connection between the first electrode and the first conductive connection member. 
     In the first aspect, the conductive soft layer of the second electrode and the conductive soft layer of the second conductive connection member may be in contact with each other with at least one of them being deformed. 
     This configuration increases the contact area and thus improves the electrical connection and the mechanical connection between the second electrode and the second conductive connection member. 
     In the first aspect, the conductive soft layer of the first electrode and the conductive soft layer of the first conductive connection member may be in contact with each other and extend into each other. 
     This configuration further increases the contact area and thus further improves the electrical connection and the mechanical connection between the first electrode and the first conductive connection member. 
     In the first aspect, the conductive soft layer of the second electrode and the conductive soft layer of the second conductive connection member may be in contact with each other and extend into each other. 
     This configuration further increases the contact area and thus further improves the electrical connection and the mechanical connection between the second electrode and the second conductive connection member. 
     A second aspect of the invention is a solar cell module including plural solar cells according to the first aspect. 
     According to the second aspect, the yield of the solar cell module can be improved. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a top view of a solar cell module of a first embodiment of the invention. 
         FIG. 2  is a perspective view of the solar cell module of the first embodiment. 
         FIG. 3  is a sectional view of a part of the solar cell module along line A-A′ in  FIG. 1 . 
         FIG. 4A  is a top view of a solar cell in the solar cell module of the first embodiment,  FIG. 4B  is a bottom view of the solar cell, and  FIG. 4C  is a sectional view of the solar cell along line B-B′ in  FIGS. 4A and 4B . 
         FIG. 5  is a sectional view of the solar cell in the solar cell module according to the first embodiment, for explaining the connection between the solar cell and conductive connection members. 
         FIG. 6A  is a top view of a solar cell in a solar cell module according to a second embodiment of the invention,  FIG. 6B  is a bottom view of the solar cell, and  FIG. 6C  is a sectional view of a part of the solar cell along line C-C′ in  FIGS. 6A and 6B . 
         FIG. 7  is a sectional view of a part of the solar cell module of the second embodiment. 
         FIG. 8A  is a top view of a solar cell of a solar cell module according to a third embodiment of the invention,  FIG. 8B  is a bottom view of the solar cell, and  FIG. 8C  is a sectional view of a part of the solar cell along line D-D′ in  FIGS. 8A and 8B . 
         FIG. 9  is a sectional view of a part of the solar cell module of the third embodiment, for explaining the connection between the solar cell and conductive connection members. 
         FIG. 10A  is a top view of a solar cell of a solar cell module of a fourth embodiment of the invention,  FIG. 10B  is a bottom view of the solar cell, and  FIG. 10C  is a sectional view of the solar cell with conductive connection members attached thereto, taken along line E-E′ in  FIGS. 10A  and  FIG. 10B . 
         FIG. 11  is a sectional view of a solar cell of a solar cell module of a fifth embodiment of the invention, for explaining the connection between the solar cell and conductive connection members. 
         FIG. 12  is a sectional view of a solar cell of a solar cell module according to a sixth embodiment of the invention, for explaining the connection between the solar cell and conductive connection members. 
         FIG. 13A  is a top view of a solar cell in a solar cell module according to a seventh embodiment of the invention,  FIG. 13B  is a bottom view of a solar cell, and  FIG. 13C  is a sectional view of the solar cell with conductive connection members attached thereto, taken along line F-F′ in  FIGS. 13A and 13B . 
         FIG. 14A  is a perspective view of a solar cell in a solar cell module according to a related art, and  FIG. 14B  is a sectional view of the solar cell. 
         FIG. 15  is a sectional view of a part of the solar cell module according to the related art, for explaining the connection between the solar cells. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Descriptions are provided herein below for embodiments based on the drawings. All of the drawings are provided to illustrate the respective examples only. No dimensional proportions in the drawings shall impose a restriction on the embodiments. For this reason, specific dimensions and the like should be interpreted with the following descriptions taken into consideration. In addition, the drawings include parts whose dimensional relationship and ratios are different from one drawing to another. 
     Note that, the same reference numerals are used to denote the same or equivalent portions in the drawings, and the description of the portions are not repeated in order to avoid redundant description. 
     Prepositions, such as “on”, “over” and “above” may be defined with respect to a surface, for example a layer surface, regardless of that surface&#39;s orientation in space. The preposition “above” may be used in the specification and claims even if a layer is in contact with another layer. The preposition “on” may be used in the specification and claims when a layer is not in contact with another layer, for example, when there is an intervening layer between them. 
     First Embodiment 
     A solar cell module of a first embodiment of the invention will be described with reference to  FIGS. 1 to 5 . 
       FIG. 1  is a top view of the solar cell module of the first embodiment of the invention.  FIG. 2  is a perspective view of the solar cell module of the first embodiment.  FIG. 3  is a sectional view of a part of the solar cell module along line A-A′ in  FIG. 1 .  FIG. 4A  is a top view of a solar cell in the solar cell module of the first embodiment,  FIG. 4B  is a bottom view of the solar cell, and  FIG. 4C  is a sectional view of the solar cell along line B-B′ in  FIGS. 4A and 4B .  FIG. 5  is a sectional view of a part of the solar cell module of the first embodiment, for explaining the connection between the solar cell and conductive connection members. 
     In  FIGS. 1 to 5 , reference number  1  designates a solar cell module. Solar cell module  1  includes a rectangular plate-like structure and frame body  8  made of metal such as aluminum and configured to support the outer peripheral edge of the structure (see  FIG. 2 ). The rectangular plate-like structure includes: transparent front cover  2  such as a transparent toughened glass; rear cover  3  being a weather-resistant member made of a resin film such as polyethylene terephthalate (PET); solar cell strings  6  provided between front cover  2  and rear cover  3 ; filling member  7 , such as ethylene vinyl acetate (EVA), filled between front cover  2  and rear cover  3  so as to fix solar cell strings  6  to front cover  2  and rear cover  3 . Each solar cell string  6  is a linear string of plural solar cells  4  in which solar cells  4  are electrically connected in series with conductive connection members  5 . Each conductive connection member  5  is formed in a band or strip shape having its width of 0.5 mm to 2 mm and its thickness of 100 to 300 μm and includes a core (main body) such as a flat copper wire and a conductive surface member coating on the core. The conductive surface member is a conductive soft layer (a conductive compliant layer) such as solder layer  5   a  made of, for example, Sn—Ag—Cu whose thickness is 5 to 40 μm. 
     Solar cell strings  6  are electrically connected in series in a manner that solar cell strings  6  are disposed parallel to each other with a distance therebetween. Specifically, conductive connection members  5  at one ends (lower ends in  FIG. 1 ) of predetermined adjacent solar cell strings  6  are solder-connected to each other by strip conductive connection member  9  made from flat plate copper wire or the like whose surface is coated with a Sn—Ag—Cu solder layer having a thickness of 20 μm. In addition, conductive connection members  5  at the other ends (upper ends in  FIG. 1 ) of different predetermined adjacent solar cell groups  6  are solder-connected to each other by L-shaped conductive connection member  10  or  11  made from flat copper wire whose surface is coated with a solder layer made of a material such as Sn—Ag—Cu having a thickness of 20 μm. In this configuration, solar cells  4  in solar cell module  1  are arranged in a matrix. 
     L-shaped conductive connection members (connection members for outputting the power of the solar cell module)  12  and  13  are solder-connected respectively to pairs of connection members  5  of solar cells  4  each positioned at the outermost edge of the electric power extraction side in the corresponding one of solar cell strings  6  positioned outermost. Each of L-shaped conductive connection members  12  and  13  is provided to extract electrical output from solar cell module  1  and is made of a flat copper wire coated with a solder layer made of a material such as Sn—Ag—Cu having a width of 1000 μm and a thickness of 40 μm. 
     Note that, an insulating member (not shown) such as an insulating sheet made of polyethylene terephthalate (PET) or the like is interposed at each point where L-shaped connection members  10  and  11  intersect with L-shaped connection members  12  and  13 , respectively. 
     In addition, although not illustrated, a leading end portion of each of L-shaped connection members  10 ,  11 ,  12  and  13  is guided, via a notch provided at rear cover  3 , to the inside of terminal box  14  provided at the upper center portion of solar cell module  1 . In terminal box  14 , bypass diodes (not shown) are provided to make connections between L-shaped connection members  12  and  10 , between L-shaped connection members  10  and  11  and between L-shaped connection members  11  and  13 , respectively. 
     Referring to  FIGS. 4 and 5 , for example, solar cells  4  each includes: p-type polycrystalline silicon substrate  15 ; n-type diffused layer  16  formed by heat diffusion of phosphorus into the front surface of p-type polycrystalline silicon substrate  15 , which is the textured surface of substrate  15 ; front surface electrodes provided on n-type diffused layer  16 ; antireflective film  18  provide on n-type diffused layer  16  in such a manner that front surface electrode  17  is exposed from antireflective film  18 ; and rear surface electrode provided on the rear surface of substrate  15 . Antireflective film  18  is made of a nitride silicon film (SiN), an oxide silicon film (SiO), or the like whose thickness is 60 nm, for example. Note that, in this embodiment, substrate  15  having a semiconductor junction such as a PN junction and antireflective film  18  correctively form a photoelectric conversion body configured to convert light into electricity. Note that the photoelectric conversion body may be a substrate having another type semiconductor junction coated with or without a film(s) or a layer(s). 
     Front surface electrode  17  is mainly made of silver. Front surface electrode  17  includes: plural fine linear finger electrodes  17   a  provided on and spread over substantially the entire front surface of substrate  15 ; and two linear bus bar electrodes  17   b  each connected to plural finger electrodes  17   a . Finger electrodes  17   a  are provided parallel to each other with a distance of 2 mm between adjacent finger electrodes  17   a . Each finger electrode  17   a  is a fine line shaped electrode which has a thickness of 10 to 30 μm and a width of 50 to 200 μm, preferably 60 to 120 μm. For example, finger electrode  17   a  has a thickness of 30 μm and a width of 90 μm, for example. Bus bar electrodes  17  each is a fine line shape electrode which has a thickness of 10 to 30 μm and a width of 0.1 to 1.8 mm, preferably 0.1 to 0.3 mm. For example, bus bar electrode has a thickness of 30 μm and a width of 0.3 mm. 
     Front surface electrode  17  is coated with solder layer (soft layer)  17   c , such as Sn—Ag—Cu, having a thickness of 1 to 10 μm, for example, 5 μm. In other words, each finger electrode  17   a  of front surface electrode  17  includes: a core (main body) thereof; and solder layer (soft layer)  17   c  coating the core and thus forming the surface of finger electrode  17   a , and each bus bar electrode  17   b  of front surface electrode  17  includes a core (main body) thereof; and solder layer (soft layer)  17   c  coating the core and thus forming the surface of bus bar electrode  17   b . Rear surface electrode  19  includes: metal film electrode  19   a  provided on and spread over substantially the entire rear surface of substrate  15 ; two bus bar electrodes  19   b  provided on metal film electrode  19   a . Metal film electrode  19   a  is made of an aluminum film whose thickness is about several μm to several mm. Linear bus bar electrode  19   b  is made mainly of silver and has a width of 300 μm and a thickness of 30 μm. 
     Each bus bar electrode  19   b  of rear surface electrode  19  is coated with solder layer (soft layer)  19   c , such as Sn—Ag—Cu, having a thickness of 1 to 10 μm (for example, 5 μm). Bus bar electrode  19   b  includes: a core (main body) thereof; and solder layer (soft layer)  19   c  coating the core and thus forming the surface of bus bar electrode  19   b.    
     Conductive connection member  5  is fixed to bus bar electrodes  17   b  of front surface electrode  17  of one of adjacent solar cells  4  and to bus bar electrodes  19   b  of rear surface electrode  19  of the other of the adjacent solar cells  4  with adhesive  20  made of epoxy-type resin, such that bus bar electrodes  17   b  of front surface electrode  17  of the one of adjacent solar cells  4  are electrically connected to bus bar electrodes  19   b  of rear surface electrode  19  of the other of the adjacent solar cells  4  with conductive connection member  5 . 
     More specifically, at one end of conductive connection member  5 , the one end of conductive connection member  5  is provided on bus bar electrode  17   b  of front surface electrode  17 , wherein adhesive  20  adheres conductive connection member  5  to finger electrode  17   a , bus bar electrode  17   b , and antireflective film  18  while solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layer(s) (soft layer(s))  17   c  of finger electrode(s)  17   a  and solder layer (soft layer)  17   c  of bus bar electrode  17   b  with solder layer  5   a  and solder layers  17   c  being deformed. In this structure, finger electrode  17   a  and bus bar electrode  17   b  extend into solder layer (soft layer)  5   a  of conductive connection member  5  without being in contact with the core of conductive connection member  5 . 
     At the other end of conductive connection member  5 , conductive connection member  5  is provided on bus bar electrodes  19   b  of rear surface electrode  19 , wherein adhesive  20  adheres conductive connection member  5  to metal film electrode  19   a  and to bus bar electrodes  19   b  while solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layer (soft layer)  19   c  of bus bar electrode  19   b  in such a manner that solder layer  5   a  of conductive connection member  5  and solder layers  19   c  of bus bar electrode  19   b  are deformed. 
     The melting points of solder layers  5   a ,  17   c  and  19   c  are higher than the cure temperature of adhesive  20 . Thus, in the connecting step of connecting conductive connection member  5  to front surface electrode  17  and/or rear surface electrode  19 , adhesive  20  adheres while solder does not melt. For example, solder layer  5   a  of conductive connection member  5 , the melting points of solder layer  17   c  of front surface electrode  17 , and solder layer  19   c  of rear surface electrode  19  are approximately 220 degrees C., and the cure temperature of adhesive  20  is approximately 200 degrees C. 
     Conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19  have, at their surface, the soft layers (solder layer  5   a , solder layer  17   c , and solder layer  19   c ) which are softer than the cores of conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19  in at least the connecting process. Note that the soft layers (solder layer  5   a , solder layer  17   c , and solder layer  19   c ) are also softer than the cores of conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19  in room temperature. The soft layer (solder layer  5   a ) of conductive connection member  5  is in contact with the soft layer (solder layer  17   c ) of finger electrodes  17   a  of front surface electrode  17  and the soft layer (solder layer  17   c ) of bus bar electrodes  17   b , and the soft layer (solder layer  5   a ) of conductive connection member  5  is in contact with the soft layer (solder layer  19   c ) of bus bar electrodes  19   b  of rear surface electrode  19 , which extends along substantially the entire length of bus bar electrode  17   b  with facing bus bar electrode  17   b  of front surface electrode  17 . 
     Therefore, in the connecting step to connect conductive connection members  5  to front surface electrode  17  and rear surface electrode  19  with adhesive  20 , the solder layers that face each other and are in contact with each other function as a cushion. Consequently, the occurrence of cracks in the solar cell can be reduced and the production yield can be improved, even if finger electrodes  17   a  and bus bar electrodes  17   b  of front surface electrode  17  are narrow in width and the heat stress in the cell thus tends to be concentrated. 
     According to the first embodiment, as described above, on the front side of solar cell  4 , solder layer  5   a  of conductive connection member  5 , which is the soft layer, is in contact with solder layer  17   c  of finger electrodes  17   a  of front surface electrode  17 , which is the soft layer, and solder layer  17   c  of bus bar electrode  17   b  of front surface electrode  17 , which is the soft layer. On the rear side of solar cell  4 , solder layer  5   a  of conductive connection member  5  which is the soft layer is in contact with solder layer  19   c  of bus bar electrode  19   b  of rear surface electrode  19 , which is the soft layer. Accordingly, in the contact state, solder layer  5   a  of conductive connection member  5  and solder layer  17   c  of front surface electrode  17  are deformed respectively and solder layer  5   a  of conductive connection member  5  and solder layer  19   c  of rear surface electrode  19  are deformed respectively. Therefore, as compared with a comparison structure wherein only one of conductive connection member  5  and front surface electrode  17  or only one of connection member  5  and rear surface electrode  19  is covered with a solder layer, the first embodiment reduces the occurrence of cracks in the solar cell and also increases the contact area between conductive connection member  5  and front surface electrode  17  and the contact area between conductive connection member  5  and rear surface electrode  19  to improve the contact states. Consequently, this improves the connection between conductive connection member  5  and front surface electrode  17 , and the connection between conductive connection member  5  and rear surface electrode  19  thereby reducing the electric resistance of the connections. 
     According to the first embodiment, fine finger electrode  17   a  and fine bus bar electrode  17   b  of front surface electrode  17  extend into solder layer  5   a  of conductive connection member  5  while the core of fine finger electrode  17   a  and the core of fine bus bar electrode  17   b  of front surface electrode  17  are not in contact with the core of conductive connection member  5 . This structure achieves an anchor effect thereby improving the connection between conductive connection member  5  and front surface electrode  17 . 
     Note that although solder layer  17   c  of front surface electrode  17  and solder layer  5   a  of conductive connection member  5  are in contact with each other with one of them extending into the other in the first embodiment, both of them may be in contact with each other and extending into each other in a modification. This modification further increases the contact area between them and improves the contact condition between them, thereby lowering the electric resistance. 
     Next, a method of manufacturing the solar cell module according to the first embodiment will be described. 
     First, a method of manufacturing solar cell  4  will be described with reference to  FIGS. 1 to 5 . 
     In the method, first, p-type polycrystalline silicon substrate  15  whose front surface is made as a textured surface by etching is prepared. 
     Next, n-type diffused layer  16  extending from the textured surface of p-type polycrystalline silicon substrate  15  to a certain depth is formed by heat diffusion of phosphorus to the textured surface. 
     Next, antireflective film  18  is formed on n-type diffused layer  16  of p-type polycrystalline silicon substrate  15  by chemical vapor deposition (CVD) with a mask covering the area where front surface electrode  17  is to be formed. 
     Next, aluminum-containing paste is formed on substantially the entire rear surface of p-type polycrystalline silicon substrate  15  by screen printing, is dried, and heated at approximately 800 C, so that metal film electrode  19   a  made of aluminum film is formed on the substantially entire rear surface. 
     Next, by a screen printing method, silver paste (conductive paste) prepared by dispersing silver powder, glass frit, etc. in an organic vehicle is printed on an exposed area, which is an area where antireflective film  18  has not been formed on the front surface of p-type polycrystalline silicon substrate  15  and is printed in a predetermined pattern on metal film electrode  19   a  of the rear surface of p-type polycrystalline silicon substrate  15 . These silver pastes are then burned at approximately 700 C, so that finger electrodes  17   a  and bus bar electrodes  17   b  which are integrally formed are provided on n-type diffused layer  16  of p-type polycrystalline silicon substrate  15  and bus bar electrodes  19   b  are provided on metal film electrode  19   a  of p-type polycrystalline silicon substrate  15 . That is, front surface electrode  17  comprising finger electrodes  17   a  and bus bar electrodes  17   b  and rear surface electrode  19  comprising metal film electrode  19   a  and bus bar electrodes  19   b  are provided on the front surface and the rear surface of substrate  15  respectively. 
     Next, in order to coat solder layers, flux containing polyalkylene glycol resin, alcohol, amine stabilizer or the like is applied on finger electrodes  17   a  of front surface electrode  17 , on bus bar electrodes  17   b  and on bus bar electrodes  19   b  of rear surface electrode  19  and then hot-air dried. Solar cell  4  having such flux thereon is dipped into solder bath, so that solder layers  17   c ,  19   c  are provided on finger electrodes  17   a  and bus bar electrodes  17   b  of front surface electrode  17  and on bus bar electrodes  19   b  of rear surface electrode  19  respectively. After providing such solder layers  17   c  and  19   c , remaining flux on solar cell  4  is removed by laundering with organic solvent such as xylene, oluene, acetonean or the like. 
     Next, plural solar cells  4  manufactured as described above are prepared, and conductive connection members  5  are prepared. Note that each conductive connection member  5  is made of a flat copper wire or the like coated with solder layer (soft layer)  5   a  by plate processing or the like. 
     Next, in order to connect conductive connection member  5  to bus bar electrodes  17   b  of front surface electrode  17  of one of adjacent solar cells  4  and to bus bar electrodes  19   b  of rear surface electrode  19  of the other of the adjacent solar cells  4 , adhesive  20  of epoxide-based resin is applied between the one of the adjacent solar cells  4  and conductive connection members  5  and is applied between the other of the adjacent solar cells  4  and conductive connection members  5 . Then, thermocompression bonding is performed at a temperature of approximately 200 degrees C., which is lower than melting points of solder layer  5   a  of conductive connection member  5  and solder layer  17   c  of front surface electrode  17  and solder layer  19   c  of bus bar electrodes  19   b  of rear surface electrode  19  and which is the curing temperature of adhesive  20 . Note that in such thermocompression bonding, solder layer  5   a  (soft layer) of conductive connection member  5  is in contact with solder layer  17   c  (soft layer) of finger electrodes  17   a  of front surface electrode  17  and solder layer  17   c  (soft layer) of bus bar electrodes  17   b  of front surface electrode  17 , while solder layer  5   a  (soft layer) of conductive connection member  5  is in contact with solder layer  19   c  (soft layer) of bus bar electrode  19   b  of rear surface electrode  19 . 
     Thus, adhesive  20  is cured in the thermocompression bonding, so that conductive connection members  5  each is mechanically and electrically connected to front surface electrode  17  of the one of adjacent solar cells  4  and to rear surface electrode  19  of the other of the adjacent solar cells  4 . Using the above process, plural solar cells  4  are connected to one another with conductive connection members  5  thereby forming solar cell string  6 . 
     After that, plural solar cell strings  6  are arranged parallel to each other, and L-shaped conductive connection members  10  and  11  and L-shaped conductive connection members (connection members for outputting the power of the solar cell module)  12  and  13  are solder-connected to conductive connection members  5  at predetermined positions, thereby forming a solar cell array. The solar cell array is disposed between transparent front cover  2  such as a transparent toughened glass and weather-resistant rear cover  3  made of a resin film such as polyethylene terephthalate (PET), with filling member  7  such as ethylene vinyl acetate (EVA) filled between front cover  2  and rear cover  3 , so as to form a rectangular plate-like structure. Then, the rectangular plate-like structure is heated. After that, metal frame body  8  and terminal box  14  is attached to the rectangular plate-like structure, so that solar cell module  1  is completed. 
     In the manufacturing method of this embodiment, solder layers  5   a  serving as soft layers of conductive connection members  5  are in contact with solder layers  17   c  serving as soft layers of finger electrodes  17   a  of front surface electrode  17  and solder layers  17   c  serving as soft layers of bus bar electrodes  17   b  of front surface electrode  17 , while solder layers  5   a  serving as soft layers of conductive connection members  5  are in contact with solder layers  19   c  serving as soft layers of bus bar electrodes  19   b  of rear surface electrode  19 . Therefore, even in a structure where thermal stress tends to be concentrated due to narrow finger electrodes  17   a  and narrow bus bar electrodes  17   b  of front surface electrode  17 , the occurrence of cracks in the solar cell can be reduced in the process of connecting conductive connection members  5  to front surface electrode  17  and to rear surface electrode  19  with adhesive  20 . This improves the production yield. 
     Second Embodiment 
     A solar cell module of the second embodiment of the invention will be described with reference to  FIGS. 6A ,  6 B,  6 C and  7 .  FIG. 6A  is a top view of a solar cell in the solar cell module,  FIG. 6B  is a bottom view of the solar cell, and  FIG. 6C  is a sectional view of a part of the solar cell with connection members connected thereto taken along line C-C′ in  FIGS. 6A and 6B .  FIG. 7  is a sectional view of a part of the solar cell module. Note that differences from the first embodiment are mainly described in the second embodiment. 
     The second embodiment is different from the first embodiment in that bus bar electrodes of rear surface electrode  19  are shorter than those of the first embodiment in the longitudinal direction and are formed in the vicinity of the edge of the rear surface of solar cell  4 . The other configurations are the same as those of the first embodiment and are designated in  FIGS. 6A to 7  by the same reference numerals as those of the first embodiment. 
     As shown in  FIGS. 6A to 7 , regarding the connection of conductive connection members  5  to the rear surface of solar cell  4 , conductive connection members  5  are electrically connected to bus bar electrodes  191   b  and  191   b  provided in the vicinity of the edge of solar cell  4 . 
     In this second embodiment, bus bar electrodes  191   b  and  191   b  of rear surface electrode  19  are provided partially along bus bar electrodes  17   b  and  17   b  of front surface electrode  17 , but are not provided along the entire length of bus bar electrodes  17   b  and  17   b . Thus, in the thermocompression bonding process, it is preferable to dispose pads or the like on the area on metal film electrode  19   a  where bus bar electrodes  17   b  and  17   b  of front surface electrode  17  are opposed to but bus bar electrodes  191   b  and  191   b  of rear surface electrode  19  do not exist. 
     According to this second embodiment, the same effects as in the first embodiment can be obtained. 
     Third Embodiment 
     A solar cell module of the third embodiment of the invention will be described with reference to  FIGS. 8A ,  8 B,  8 C, and  9 .  FIG. 8A  is a top view of a solar cell of the solar cell module,  FIG. 8B  is a bottom view of the solar cell, and  FIG. 8C  is a sectional view of a part of the solar cell along line D-D′ in  FIGS. 8A and 8B .  FIG. 9  is a sectional view of a part of the solar cell module of the third embodiment, for explaining the connection between the solar cell and conductive connection members. Note that differences from the first embodiment are mainly described in the third embodiment. 
     The third embodiment is different from the first embodiment in that front surface electrode  17  has no bus bar electrode (that is, the front surface electrode  17  has no bus bar structure). The other configurations in the third embodiment are the same as those of the first embodiment and are designated in  FIGS. 8A to 9  by the same reference numerals. 
     With reference to  FIGS. 8A to 9 , front surface electrode  17  of solar cell  4  will be described below. 
     Front surface electrode  17  is made mainly of silver, and comprises plural fine linear finger electrodes  17   a  spreading over substantially the entire front surface of substrate  15 . In the third embodiment, finger electrodes  17   a  are fine line-shaped electrodes with a distance of 2 mm therebetween and each having a thickness of 10 to 30 μm (for example, 30 μm) and a width of 50 to 200 μm, preferably 60 to 120 μm (for example, 90 μm). 
     The surface of front surface electrode  17  is coated with solder layer (soft layer)  17   c  made of a material such as Sn—Ag—Cu having a thickness of 1 to 10 μm (for example, 5 μm). In other words, each finger electrode  17   a  of front surface electrode  17  includes: a core (main body) thereof and solder layer (soft layer)  17   c  coating the core and thus comprising the surface of finger electrode  17   a . Rear surface electrode  19  has the same structure as the first embodiment, that is, rear surface electrode  19  includes: metal film electrode  19   a  formed on the substantially entire rear surface of substrate  15 ; two wide bus bar electrodes  19   b  and  19   b  provided on metal film electrode  19   a . Metal film electrode  19   a  is made of an aluminum film whose thickness is about several μm to several mm. Bus bar electrode  19   b  is made mainly of silver and has a width of 0.3 mm and a thickness of 30 μm. 
     The surface of bus bar electrode  19   b  of rear surface electrode  19  is coated with solder layer (soft layer)  19   c  made of a material such as Sn—Ag—Cu having a thickness of 1 to 10 μm (for example, 5 μm). In other words, bus bar electrode  19   b  of rear surface electrode  19  includes: the core (main body) thereof; and solder layer (soft layer)  19   c  covering the core and thus comprising the surface of bus bar electrode  19   b.    
     Bus bar electrodes  17   b  and  17   b  of front surface electrode  17  of one of adjacent solar cells  4  and  4  is electrically connected to bus bar electrodes  19   b  and  19   b  of rear surface electrode  19  with conductive connection members  5  and  5 , in such a manner that conductive connection members  5  and  5  are fixed to bus bar electrodes  17   b  and  17   b  and to bus bar electrodes  19   b  and  19   b  with adhesive  20  made of epoxy-type resin. 
     More specifically, regarding one end of conductive connection member  5 , the one end of conductive connection member  5  is provided on finger electrodes  17   a  of front surface electrode  17  with a bond of adhesive  20  between antireflective film  18  and conductive connection member  5  and between finger electrodes  17   a  and conductive connection member  5  in such a manner that solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layers (soft layers)  17   c  of finger electrodes  17   a  and finger electrodes  17   a  are digged into solder layer (soft layer)  5   a  of conductive connection member  5 . 
     Regarding the other end of conductive connection member  5 , conductive connection member  5  is provided on bus bar electrodes  19   b  of rear surface electrode  19  with a bond of adhesive  20  between metal film electrode  19   a  and conductive connection member  5  and between bus bar electrode  19   b  and conductive connection member  5 , in such a manner that solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layers (soft layers)  19   c  of bus bar electrode  19   b.    
     The melting points of solder layer  5   a ,  17   c , and  19   c  are higher than the curing temperature of adhesive  20 . In the process of connecting conductive connection members  5  and  5  to front surface electrode  17  and to rear surface electrode  19 , the bonding by using adhesive  20  is achieved without melting the solders. For example, the melting temperatures of solder layer  5   a  of conductive connection member  5 , solder layer  17   c  of front surface electrode  17 , and solder layer  19   c  of rear surface electrode  19  are approximately 220 degrees C., whereas the curing temperature of adhesive  20  is approximately 200 degrees C. 
     In this third embodiment, conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19  have, at their surfaces, solder layer (soft layer)  5   a , solder layer (soft layer)  17   c , solder layer (soft layer)  19   c  which are made of materials softer than the cores of conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19 , respectively, at room temperature. Solder layer  5   a  serving as a soft layer of conductive connection member  5  is in contact with solder layer(s)  17   c  serving as soft layer(s) of finger electrode(s)  17   a  of front surface electrode  17  and solder layer  5   a  serving as a soft layers of conductive connection member  5  is in contact with solder layer  19   c  serving as a soft layer of bus bar electrode  19   b  of rear surface electrode  19 . With this configuration, cushioning characteristics of the solder layers that face (contact with) each other reduce the occurrence of cracks in solar cell  4  in the process of connecting conductive connection members  5  to front surface electrode  17  and to rear surface electrode  19  with adhesive  20 , even in a structure where the thermal stress in solar cell  4  tends to be concentrated due to narrow finger electrodes  17   a  of front surface electrode  17 . This improves the production yield. 
     Further, as described above, solder layer  5   a  serving as the soft layer of conductive connection member  5  is contact with solder layer  17   c  serving as the soft layer of finger electrode  17   a  of front surface electrode  17  and solder layer  17   c  serving as the soft layer of bus bar electrodes  17   b  of front surface electrode  17 , and solder layer  5   a  serving as the soft layer of conductive connection member  5  is contact with solder layer  19   c  serving the soft layer of bus bar electrode  19   b  of rear surface electrode  19 . In this structure, solder layer  5   a  of conductive connection member  5  is contact with solder layer  17   c  of front surface electrode  17  with both solder layer  5   a  and solder layer  17   c  being deformed and solder layer  5   a  of conductive connection member  5  is contact with solder layer  19   c  of rear surface electrode  19  with both solder layer  5   a  and solder layer  17   c  being deformed in the connecting process. Accordingly, in addition to reducing the occurrence of cracks in solar cell  4 , this structure increases the contact area and improves the contact condition, as compared to a comparative structure where one of conductive connection member  5  and front surface electrode  17  is coated with a solder layer or one of conductive connection member  5  and rear surface electrode  19  is coated with a solder layer. Therefore, the contact between conductive connection member  5  and front surface electrode  17  and the contact between conductive connection member  5  and rear surface electrode  19  are improved, and this reduces the electric resistance of these contacts. 
     Further, according to this embodiment, narrow finger electrodes  17   a  of front surface electrode  17  are not in contact with the core of conductive connection member  5  and extend into solder layer  5   a  of conductive connection member  5 , and this achieves an anchor characteristic, that is, narrow finger electrodes  17   a  are anchored to conductive connection member  5 . Therefore, this brings about a preferable connection between conductive connection member  5  and front surface electrode  17 . 
     Note that the soft layers that are in contact with each other may extend into each other. In this modification, the contact area is further increased and the contact condition is further improved, this reduces the electric resistance of the contact. 
     The method of manufacturing the solar cell module of the third embodiment is the same as or similar to that of the first embodiment, and thus can achieve the same effects as the manufacturing method of the first embodiment. 
     Fourth Embodiment 
     Next, a solar cell module according to the fourth embodiment of the invention will be described with reference to  FIGS. 10A to 10C .  FIG. 10A  is a top view of a solar cell of the solar cell module,  FIG. 10B  is a bottom view of the solar cell, and  FIG. 10C  is a sectional view of the solar cell with conductive connection members attached thereto, taken along line E-E′ in  FIGS. 10A and 10B . Note that in the fourth embodiment, differences from the third embodiment will be mainly described below. 
     The fourth embodiment is different from the third embodiment in that rear surface electrode  19  having the same configuration as that of the second embodiment, that is, the bus bar electrodes of rear surface electrode  19  have a short length along the longitudinal direction thereof and are formed in the vicinity of the edge of the rear surface of solar cell  4 . The other configurations in the fourth embodiment are the same as those of the third embodiment and are designated in  FIGS. 10A to 10C  by the same reference numerals as those of the third embodiment. 
     As shown in  FIGS. 10A to 10C , regarding the connection of conductive connection members  5  and  5  to the rear surface of solar cell  4 , conductive connection members  5  and  5  are electrically connected to bus bar electrodes  191   b  and  191   b  which are provided in the vicinity of the edge of the rear surface of the solar cell  4 . 
     In the fourth embodiment, no bus bar electrode of front surface electrode  17  is provided along the entire length of bus bar electrodes  191   b  and  191   b  of rear surface electrode  19 . Accordingly, in the thermocompression bonding process, it is preferable to dispose pads or the like on the front surface at the area opposed to bus bar electrodes  191   b  and  191   b.    
     According to the fourth embodiment, the same effects as in the third embodiment can be obtained. 
     Fifth Embodiment 
     A solar cell module of the fifth embodiment of the invention will be described below with reference to  FIG. 11 .  FIG. 11  is a sectional view of a solar cell in the solar cell module. Note that, in the fifth embodiment, differences from the first embodiment will be mainly described below. 
     The fifth embodiment is different from the first embodiment in that adhesive  20  includes therein conducting particles  20   a , that is, adhesive  20  is a so-called electrically-conducting adhesive and finger electrodes  17   a  and bus bar electrodes  17   b  are do not extend into solder layer (soft layer)  5   a  and  5   a  of conductive connection members  5  and  5 . The other configurations are the same as in the first embodiment and are designated by the same reference numerals. 
     Conducting particles  20   a  are nickel particles or silver particles and may be Ag-coated nickel particles, metal-coated plastic particles such as Ag-coated plastic particles, silver-coated plastic particles, or the other conducting particles. The maximum particle diameter of conducting particles  20   a  is, for example, 20 μm. 
     Bus bar electrodes  17   b  of front surface electrode  17  of one of adjacent solar cells  4  and  4  are electrically connected to bus bar electrodes  19   b  of rear surface electrode  19  of the other of the adjacent solar cells  4  and  4  with conductive connection members  5  and  5  in such a manner that adhesive  20  of epoxy-type resin bonds conductive connection members  5  and  5  to solar cells  4  and  4 . 
     More specifically, regarding one end of conductive connection member  5 , the one end of conductive connection member  5  is provided on bus bar electrode  17   b  of front surface electrode  17  with a bond of adhesive  20  between antireflective film  18  and conductive connection member  5 , between finger electrode(s)  17   a  and conductive connection member  5 , and between bus bar electrode  17   b  and conductive connection member  5 , wherein solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layer (soft layer)  17   c  of finger electrode(s)  17   a  and with solder layer (soft layer)  17   c  of bus bar electrode  17   b.    
     Regarding the other end of conductive connection member  5 , the other end of conductive connection member  5  is provided on bus bar electrode  19   b  of rear surface electrode  19  with a bond of adhesive  20  between metal film electrode  19   a  and conductive connection member  5  and between bus bar electrode  19   b  and conductive connection members  5 , wherein solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layer (soft layer)  19   c  of bus bar electrode  19   b.    
     In the fifth embodiment, conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19  have, at their surfaces, solder layer (soft layer)  5   a , solder layer (soft layer)  17   c , solder layer (soft layer)  19   c  which are softer than the cores of conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19 , respectively, at room temperature. Solder layer  5   a  serving as a soft layer of conductive connection member  5  is opposed to and in contact with solder layer(s)  17   c  serving as soft layer(s) of finger electrode(s)  17   a  of front surface electrode  17  and is opposed to and in contact with solder layer  17   c  serving as a soft layer of bus bar electrode  17   b  of front surface electrode  17 . Further, solder layer  5   a  serving as a soft layer of conductive connection member  5  is opposed to and in contact with solder layer  19   c  serving as a soft layer of bus bar electrode  19   b  of rear surface electrode  19 . With this configuration, cushioning characteristics of the solder layers that face (contact with) each other reduce the occurrence of cracks in solar cell  4  in the process of connecting conductive connection members  5  to front surface electrode  17  and to rear surface electrode  19  with adhesive  20 , even in a structure where the thermal stress in solar cell  4  tends to be concentrated due to narrow finger electrodes  17   a  and narrow bus bar electrodes  17   b  of front surface electrode  17  with conducting particles  20   a . This improves the production yield. 
     The fifth embodiment is different from the first embodiment in that finger electrodes  17   a  and bus bar electrodes  17   b  do not extend into solder layer (soft layer)  5   a  of conductive connection member  5 . However, conducting particles  20   a  do extend into solder layer  5   a  of conductive connection member  5  and into solder layer  17   c  of front surface electrode  17  on the front side, and conducting particles  20   a  extend into solder layer  5   a  of conductive connection member  5  and into solder layer  19   c  of rear surface electrode  19  on the rear side, thereby improving the contact condition therebetween. Accordingly, this improves the electric connection between conductive connection member  5  and front surface electrode  17  and the electric connection between conductive connection member  5  and rear surface electrode  19 , thereby reducing the electric resistances thereof. Further, anchor characteristic of conducting particles  20   a  extending into members  5   c  and  17   c  and members  5   c  and  19   c  brings about a preferable connection between conductive connection member  5  and front surface electrode  17  and a preferable connection between conductive connection member  5  and rear surface electrode  19 . 
     Although finger electrode  17   a  and bus bar electrode  17   b  do not extend into solder layer (soft layer)  5   a  of conductive connection member  5  in the fifth embodiment, finger electrode  17   a  and bus bar electrode  17   b  may extend into solder layer (soft layer)  5   a  of conductive connection member  5  like the first embodiment. 
     Note that it is preferable to set the condition of thermocompression bonding in addition to the thickness of solder layer  5   a  of conductive connection member  5 , the thickness of solder layer  17   c  of front surface electrode  17 , and the thickness of solder layer  19   c  of rear surface electrode  19 , in order to prevent conducting particles  20   a  from being in contact with the core of conductive connection member  5 , the core of front surface electrode  17 , and the core of rear surface electrode  19 . 
     The method of manufacturing the solar cell module in the fifth embodiment is the same as or similar to that of the first embodiment, and thus can achieve the same effects as the manufacturing method of the first embodiment. 
     Sixth Embodiment 
     A solar cell module of the sixth embodiment of the invention will be described with reference to  FIG. 12 .  FIG. 12  is a cross sectional view of a solar cell of the solar cell module according to the sixth embodiment. Note that differences from the fifth embodiment will be mainly described below in the sixth embodiment. 
     The sixth embodiment is different from the fifth embodiment in that front surface electrode  17  includes no bus bar electrode (that is, front surface electrode  17  has no-bus-bar structure). The other configurations are the same as in the fifth embodiment and are designated by the same reference numerals. 
     The sixth embodiment has front surface electrode  17  having the no-bus-bar structure and can achieves the same effects as in the fourth embodiment. 
     Seventh Embodiment 
     A solar cell module of the seventh embodiment of the invention will be described below with reference to  FIGS. 13A to 13C .  FIG. 13A  is a top view of a solar cell in the solar cell module,  FIG. 13B  is a bottom view of the solar cell, and  FIG. 13C  is a sectional view of the solar cell with conductive connection members attached thereto taken along line F-F′ in  FIGS. 13A and 13B . Note that in the seventh embodiment, differences from the first embodiment will be mainly described below. 
     In the seventh embodiment, each of solar cells  4  is a HIT solar cell. Either of a front surface electrode or a rear surface electrode of solar cell  4  has plural fine linear finger electrodes and two bus bar electrodes connected with the finger electrodes. 
     As shown in  FIGS. 13A to 13C , solar cell  4  is a so-called HIT solar cell, wherein i-type amorphous silicon layer  31 , p-type amorphous silicon layer  32 , and transparent conductive layer  33  such as ITO are provided in this order on substantially the entire region of the textured front surface of n-type single-crystalline silicon substrate  30  and wherein i-type amorphous silicon layer  34 , n-type amorphous silicon layer  35 , and transparent conductive layer  36  such as ITO are provided in this order on substantially the entire region of a textured rear surface of substrate  30 . Front surface electrode  37  is provided on transparent conductive layer  33 , and rear surface electrode  39  is provided on transparent conductive layer  36 . 
     Front surface electrode  37  is mainly made of silver. Front surface electrode  37  includes: plural fine linear finger electrodes  37   a  disposed on and spread over substantially the entire surface of transparent conductive layer  33 ; and two linear bus bar electrodes  37   b  and  37   b  each connected to plural finger electrodes  37   a . Finger electrodes  37   a  are provided every 2 mm and each is a fine line shaped electrode whose thickness is 10 to 30 μm (for example, 30 μm) and whose width is 50 to 200 μm, preferably 60 to 120 μm (for example, 90 μm). Bus bar electrodes  37  each is a fine line shape electrode whose thickness is 10 to 30 μm (for example, 30 μm) and whose width is 0.1 to 1.8 mm, preferably 0.1 to 0.3 mm (for example, 0.3 mm). Front surface electrode  37  is coated with solder layer (soft layer)  37   c , such as Sn—Ag—Cu, having a thickness of 1 to 10 μm (for example, 5 μm). In other words, each finger electrode  37   a  includes: a core (main body) thereof; and solder layer (soft layer)  37   c  coating the core and thus comprising the surface of finger electrode  37   a , and each bus bar electrode  37   b  includes: a core (main body) thereof; and solder layer (soft layer)  37   c  coating the core and comprising the surface of bus bar electrode  37   b.    
     Rear surface electrode  39  is mainly made of silver. Rear surface electrode  39  includes: plural fine linear finger electrodes  39   a  provided on and spread over substantially the entire surface of transparent conductive layer  36 ; two fine bus bar electrodes  39   b  each connected with plural finger electrodes  39   a . In this embodiment, finger electrodes  39   a  are located every 2 mm and each is a fine line shaped electrode whose thickness is 10 to 30 μm (for example, 30 μm) and whose width is 50 to 200 μm, preferably 60 to 120 μm (for example, 90 μm). Bus bar electrodes  39   b  each is a fine lined shape electrode whose thickness is 10 to 30 μm (for example, 30 μm) and whose width is 0.1 to 1.8 mm, preferably 0.1 to 0.3 mm (for example, 0.3 mm). 
     Rear surface electrode  39  is coated with solder layer (soft layer)  39   c , such as Sn—Ag—Cu, having a thickness of 1 to 10 μm, (for example, 5 μm). That is, each finger electrode  39   a  includes: a core (main body) thereof and solder layer (soft layer)  39   c  coating the core and thus comprising the surface of finger electrode  39   a , and each bus bar electrode  39   b  includes: a core (main body) thereof; and solder layer (soft layer)  39   c  coating the core and thus comprising the surface of bus bar electrode  39   b.    
     Bus bar electrodes  37   b  and  37   b  of front surface electrode  37  of one of adjacent solar cells  4  and  4  are electrically connected to bus bar electrodes  39   b  and  39   b  of rear surface electrode  39  of the other of the adjacent solar cells  4  and  4  with conductive connection members  5  and  5 , in such a manner that conductive connection members  5  and  5  are fixed to bus bar electrodes  37   b  and  37   b  and bus bar electrodes  39   b  and  39   b  with adhesive  20  made of epoxy-type resin. 
     That is, regarding one end of conductive connection member  5 , the one end of conductive connection member  5  is provided on the bus bar electrodes  37   b  and  37   b  of front surface electrode  37  with a bond of adhesive  20  between transparent conductive layer  33  and conductive connection member  5  and between finger electrode(s)  37   a  and conductive connection member  5  and between bus bar electrode  37   b  and conductive connection member  5 , wherein solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layer (soft layer)  37   c  of finger electrode(s)  37   a  and with solder layer (soft layer)  37   c  of bus bar electrode  37   b  in such a manner that finger electrode(s)  37   a  and bus bar electrode  37   b  extend into solder layer (soft layer)  5   a  of conductive connection member  5 . 
     Regarding the other end of conductive connection member  5 , conductive connection member  5  is provided on bus bar electrode  39   b  of rear surface electrode  39  with a bond of adhesive  20  between transparent conductive layer  36  and conductive connection member  5  and between finger electrode(s)  39   a  and conductive connection member  5  and between bus bar electrode  39   b  and conductive connection member  5 , wherein solder layer (soft layer)  5   a  of conductive connection member  5  is in contact with solder layer (soft layer)  39   c  of finger electrode(s)  39   a  and with solder layer (soft layer)  39   c  of bus bar electrode  39   b  in such a manner that finger electrode(s)  39   a  and bus bar electrode  39   b  extend into solder layer (soft layer)  5   a  of conductive connection member  5 . 
     The melting points of solder layers  5   a ,  37   c , and  39   c  are higher than the curing temperature of adhesive  20 . In the process of connecting conductive connection members  5  and  5  to front surface electrode  37  and to rear surface electrode  39 , the bonding using adhesive  20  is thus achieved without melting the solders. For example, the melting points of solder layer  5   a  of conductive connection member  5 , solder layer  37   c  of front surface electrode  37 , solder layer  39   c  of rear surface electrode  39  are approximately 220 degrees C., whereas the curing temperature of adhesive  20  is approximately 200 degrees C. 
     In this embodiment, conductive connection member  5 , front surface electrode  37 , and rear surface electrode  39  have, at their surface, solder layer  5   a  (soft layer), solder layer  37   c  (soft layer), solder layer  39   c  (soft layer) which are made of materials softer than the cores of conductive connection member  5 , front surface electrode  17 , and rear surface electrode  19 , respectively, at room temperature. On the front side, Solder layer  5   a  serving as the soft layer of conductive connection member  5  is in contact with solder layer  37   c  serving as the soft layer of finger electrodes  37   a  of front surface electrode  37  and with solder layer  37   c  serving as the soft layer of bus bar electrode  37   b  of front surface electrode  37 . On the rear side, solder layer  5   a  serving as the soft layer of conductive connection member  5  is contact with solder layer(s)  39   c  serving as the soft layer(s) of finger electrode(s)  39   a  of rear surface electrode  39  and with solder layer  39   c  serving as the soft layer of bus bar electrode  39   b  of rear surface electrode  39 . With this configuration, cushioning characteristics of the solder layers that face (contact with) each other reduce the occurrence of cracks in solar cell  4  in the process of connecting conductive connection members  5  to front surface electrode  37  and to rear surface electrode  39  with adhesive  20 . This improves the production yield. 
     Further, according to this embodiment, solder layer  5   a  of conductive connection member  5  and solder layer  37   c  of front surface electrode  37  are in contact with each other with both being deformed while solder layer  5   a  of conductive connection member  5  and solder layer  39   c  of rear surface electrode  39  are in contact with each other with both being deformed. 
     Accordingly, this structure increases the contact area and improves the contact condition, as compared to a comparative structure where one of conductive connection member  5  and front surface electrode  37  is coated with a solder layer or one of conductive connection member  5  and rear surface electrode  39  is coated with a solder layer. Therefore, the contact between conductive connection member  5  and front surface electrode  37  and the contact between conductive connection member  5  and rear surface electrode  39  are improved, and this reduces the electric resistance of these contacts. 
     Further, according to this embodiment, narrow finger electrodes  37   a  and narrow bus bar electrodes  37   b  of front surface electrode  37  extend into solder layer  5   a  of conductive connection member  5 , and narrow finger electrodes  39   a  and narrow bus bar electrodes  39   b  of rear surface electrode  39  extend into solder layer  5   a  of conductive connection member  5 , thereby achieving anchor characteristics. Therefore, this brings about a preferable connection between conductive connection member  5  and front surface electrode  37  and a preferable connection between conductive connection member  5  and rear surface electrode  39 . 
     According to the manufacturing method of this embodiment, the same effects as in the first embodiment can be obtained. 
     Although the solder of Sn—Ag—Cu alloy is used as the conductive soft layer in the above embodiments, various types of solders such as Au—Si alloy, Au—Ge alloy, Au—Sn alloy, Sn—Cu alloy, Sn—Ag alloy, Sn—Au alloy, Sn—Ag—Cu alloy, Pb—Au alloy, Sn—Ag—In alloy, Sn—Pb alloy, or the like may be used. 
     As described above, the resin adhesive may be an electrical insulation adhesive or an electrical conductive adhesive. 
     In the fifth and sixth embodiments, the electrically-conducting adhesive containing the conducting particles such as Ni, Ag or the like is used as the resin adhesive. However, the electrically-conducting adhesive may include nonconductive particles (nonconductive materials) such as SiO 2 , may include both conducting particles and nonconductive particles, or may include neither conducting particles nor nonconductive particles. 
     In the first to seventh embodiments, the conductive soft layer is provided on the entire area of the front surface electrode. However, the conductive soft layer may be provided only on an opposed area that faces the conductive connection member, or may be provided only on the opposed area in such a manner that the conductive soft layer is not provided on a part of the opposed area. 
     In the above embodiments, the conductive soft layer is provided on the front surface electrode and on the rear surface electrode. However, a structure in which the conductive soft layer is provided on either the front surface electrode or the rear surface electrode can achieve similar effects to the above embodiment. 
     Although the solar cells in the above embodiments are described using polycrystalline solar cells and HIT solar cells, various solar cells such as single-crystalline solar cells can be appropriately used. 
     Further, the solar cell module of the invention is not limited to the above embodiments. For example, the solar cell module of the invention may have no frame body although the solar cell module in the above embodiments has frame body  8 . 
     The invention may be applied to a bifacial solar cell module, for example, each of front cover  2  and rear cover  3  may be made of a glass plate. 
     The number of the bus bar electrodes of the front surface electrode and the number of the bus bar electrodes of the rear surface electrode may be appropriately changed, respectively. 
     The embodiment disclosed in this description is to be considered as only exemplary and not intended to impose any limitation. It is intended that the scope of the invention is not limited by the embodiment described above, but by the scope of claims appended hereto, and that the scope of the invention include all modifications within the scope of claims and the equivalents to the claims.