Patent Publication Number: US-2012037203-A1

Title: Wiring sheet, solar cell with wiring sheet, solar cell module, and method for fabricating solar cell with wiring sheet

Description:
TECHNICAL FIELD 
     The present invention relates to wiring sheets, solar cells with wiring sheets, solar cell modules, and methods for fabricating solar cells with wiring sheets. 
     BACKGROUND ART 
     In recent years, development of clean energy is demanded for environmental issues such as shortage of energy resources, increasing CO 2  in the atmosphere, and the like, and in particular, solar photovoltaic power generation employing solar cell modules are developed, put to practical use and advanced as a new energy resource. 
     Such a solar cell module is configured of solar cells, the mainstream of which has conventionally been a solar cell for example having a monocrystalline or polycrystalline silicon substrate having a photoreceptive surface with an impurity of a conduction type opposite to that of the silicon substrate diffused therein to provide a pn junction, and a back surface opposite to the photoreceptive surface, with the surfaces provided with electrodes, respectively, i.e., a bifacial solar cell. Furthermore, in recent years, a solar cell having a silicon substrate having a back surface with both an electrode for p type and an electrode for n type, i.e., a so called back electrode type solar cell, is also being developed. 
     For example, U.S. Pat. No. 5,951,786 (patent literature 1) discloses a solar cell module including an insulating base material, an electrically conductive wiring patterned on a surface of the insulating base material, and a back electrode type solar cell overlying the wiring and electrically connected thereto. 
     CITATION LIST 
     Patent Literature  
     PTL 1: U.S. Pat. No. 5,951,786 
     SUMMARY OF INVENTION 
     Technical Problem  
     Patent literature 1 describes a configuration of a solar cell module that can be fabricated for example as follows: 
     With reference to  FIG. 8 , initially, an insulating base material  11  formed for example of a polymeric material is prepared and on a surface thereof a patterned wiring  16  is formed. 
     Subsequently, the electrodes (not shown) of a plurality of back electrode type solar cells  20  are bonded with an electrically conductive adhesive to wiring  16  patterned on the surface of insulating base material  11 . The plurality of back electrode type solar cells  20  are thus electrically connected to wiring  16  on the surface of insulating base material  11  to fabricate solar cells with a wiring sheet. 
     The back electrode type solar cells electrically connected to wiring  16  on the surface of insulating base material  11  are pressed to a sealing material  31  disposed between a glass or similar, transparent substrate  30  and back electrode type solar cells  20  and between a back surface protection sheet  32  and a wiring sheet  10  and are heated. The back electrode type solar cells with the wiring sheet (i.e., back electrode type solar cells  20  and wiring sheet  10 ) are thus sealed in the sealing material. A solar cell module is thus fabricated. 
     In general, a wiring sheet can be formed of an insulating film material, and copper, aluminum or similar foil of approximately 50 μm or smaller in thickness bonded thereto, and can be etched to have a circuit pattern thereon. A method has been studied to bond cells&#39; electrodes with an electrically conductive adhesive or the like in accordance with the sheet&#39;s electrode pattern. This method, in contrast to a conventional solar cell wiring method, does not require connecting from the cell&#39;s back electrode to front electrode via a tub line and thus allows cells to be spaced by a distance smaller than conventional. This allows a solar cell module to provide more efficient conversion and can reduce its construction cost per output. 
     A typical solar cell module has cells sealed by a sealing material. More specifically, the cells are sealed in the step for example of sandwiching a wired cell group by the sealing material in the form of sheet, applying pressure and in that condition, applying a temperature of approximately 120-150° C. to melt the sealing material, and cooling it to room temperature and thus setting it. This sealing step may thermally contract/expand the wiring sheet. Furthermore, a temperature cycle caused in a market environment may also thermally contract/expand the wiring sheet. In some case, there is even a possibility that the wiring sheet is thermally deformed to project toward solar cells and thus has a wiring brought into contact with a portion other than an electrode of a solar cell. 
     In other words, the sealing step involving a heat treatment, setting the solar cell module in an environment of high temperature, and the like thermally contract/expand the wiring sheet, which may result in unwanted contact between a back electrode type solar cell and a wiring of the wiring sheet, and furthermore, unsatisfactory insulation, electrical leakage, and short circuit. 
     Furthermore, if a back electrode type solar cell has an electrode misaligned from a wiring of the wiring sheet, the wiring and the electrode contact each other in a reduced area resulting in an increased contact resistance, and if a cell has an electrode misaligned in a large amount, the electrodes different in conduction type (p type/n type) and a wiring may short-circuit. 
     Such misalignment includes initial misalignment, and misalignment in a process, an environment for installation, and the like. Initial misalignment is attributed to a cell&#39;s dimensional tolerance, the precision in forming the cell&#39;s electrodes, a wiring&#39;s dimensional tolerance, the precision in forming the wiring, and the precision in mounting the cell on the wiring. Accordingly, the wiring must be spaced to avoid short circuit with the combination of these tolerances considered. 
     Misalignment in a process, an environment for installation, and the like is caused for example when the aforementioned process involving a heat treatment thermally contracts/expands the wiring sheet and as a result a back electrode type solar cell may have an electrode misaligned relative to a wiring of the wiring sheet. In addition, the aforementioned sealing step fluidizes the sealing material, which may also misalign the wiring sheet relative to a back electrode type solar cell or vice versa. 
     In view of the above circumstances, the present invention contemplates a wiring sheet for a back electrode type solar cell, a solar cell with the wiring sheet, a solar cell module, and a method for fabricating the solar cell with the wiring sheet, that can reduce/prevent unwanted contact between the back electrode type solar cell disposed on the wiring sheet and a wiring of the wiring sheet. 
     The present invention also contemplates a wiring sheet for a back electrode type solar cell, a solar cell with the wiring sheet, a solar cell module, and a method for fabricating the solar cell with the wiring sheet, that can reduce/prevent misalignment of an electrode of the back electrode type solar cell relative to a wiring of the wiring sheet. 
     Solution to Problem  
     The present invention provides a wiring sheet including an insulating base material and a wiring disposed on the insulating base material for electrically connecting a back electrode type solar cell, the wiring sheet having a plane with a cell mounting portion for mounting the back electrode type solar cell thereon, the wiring sheet being provided with an insulation layer at the plane on a surface of at least a portion of a region excluding the cell mounting portion, the insulation layer extending to cover at least a portion of a peripheral region of the cell mounting portion. 
     Preferably, the insulation layer has a surface similar in color to a photoreceptive surface of the back electrode type solar cell. 
     Preferably, the insulation layer has a white surface. 
     Preferably, the wiring sheet further includes a plurality of cell mounting portions and is provided with the insulation layer between adjacent ones of the cell mounting portions. 
     Preferably, the insulation layer is provided on the wiring. 
     Preferably, the wiring includes a comb-like portion formed of a plurality of teeth for electrical connection to the back electrode type solar cell and a connection portion connecting the teeth, and the insulation layer is provided in a region including a portion at which the teeth are connected to the connection portion. 
     Furthermore, the present invention provides a solar cell with a wiring sheet, including: a wiring sheet having an insulating base material and a wiring provided on the insulating base material; and a back electrode type solar cell having a photoreceptive surface and an opposite surface provided with an electrode, the wiring sheet being provided with the back electrode type solar cell on a plane, the wiring sheet being provided with an insulation layer at the plane on a surface of at least a portion of a region excluding a cell mounting portion on which said back electrode type solar cell is mounted, the insulation layer partially extending to the cell mounting portion between the back electrode type solar cell and the wiring sheet. 
     Preferably, the insulation layer has a surface similar in color to the photoreceptive surface of the back electrode type solar cell. 
     Preferably, the insulation layer has a white surface. 
     Preferably, the solar cell with the wiring sheet further includes a plurality of back electrode type solar cells and is provided with the insulation layer between adjacent ones of the back electrode type solar cells. 
     Preferably, the insulation layer is provided on the wiring. 
     Preferably, the wiring includes a comb-like portion formed of a plurality of teeth and a connection portion connecting the teeth, the electrode forms a group of electrodes connected to the wiring at the plurality of teeth, and at least a portion of a region outer than the group of electrodes on a surface of the back electrode type solar cell provided with the group of electrodes is covered with the insulation layer. 
     Furthermore, the present invention provides a solar cell module having the solar cell with the wiring sheet as described above sealed with a sealing material. 
     Furthermore, the present invention provides a method for fabricating a solar cell with a wiring sheet, including a wiring sheet having an insulating base material and a wiring provided on the insulating base material, and a back electrode type solar cell having a photoreceptive surface and an opposite surface provided with an electrode, the method including the steps of: providing an insulation layer on a plane having a cell mounting portion for mounting the back electrode type solar cell thereon; and disposing the back electrode type solar cell on the wiring sheet such that a peripheral region of the back electrode type solar cell is superposed on a portion of the insulation layer. 
     Advantageous Effects of Invention  
     The present invention can provide a wiring sheet having an insulation layer at a cell mounting side between cell mounting portions so that if the wiring sheet is deformed the wiring sheet is prevented from having a wiring brought into contact with a portion of a back electrode type solar cell other than a wiring and thus reduces/prevents unsatisfactory insulation, electrical leakage and short circuit, and a product having excellent characteristics can thus be implemented. 
     Furthermore, the present invention can provide a wiring sheet having an insulation layer at a cell mounting side between cell mounting portions so that it reduces/prevents misalignment between the wiring sheet and a back electrode type solar cell and hence wiring-electrode contact resistance reduction, short circuit and the like, and a product having excellent characteristics can thus be implemented. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1(   a ) is a schematic plan view of one example of a wiring sheet in accordance with the present invention, as seen at a side thereof provided with wiring, and  FIG. 1(   b ) is a schematic cross section taken along a line B-B shown in  FIG. 1(   a ). 
         FIG. 2(   a ) is a schematic cross section of one example of a back electrode type solar cell electrically connected to a wiring of a wiring sheet in accordance with the present invention, and  FIG. 2(   b ) is a schematic plan view of one example of a back surface of a semiconductor substrate of the back electrode type solar cell shown in FIG.  2 ( a ). 
         FIG. 3(   a ) is a schematic plan view of another example of the back surface of the semiconductor substrate of the back electrode type solar cell shown in  FIG. 2(   a ), and  FIG. 3(   b ) is a schematic plan view of still another example of the back surface of the semiconductor substrate of the back electrode type solar cell shown in  FIG. 2(   a ). 
         FIG. 4(   a ) is a schematic plan view of one example of a solar cell with a wiring sheet in accordance with the present invention, as seen at its photoreceptive surface, and  FIG. 4(   b ) is a schematic cross section taken along a line B-B shown in  FIG. 4(   a ). 
         FIGS. 5(   a ) and  5 ( b ) are schematic cross sections of an example of a solar cell with a wiring sheet in accordance with the present invention, taken along a line A-A shown in  FIG. 4(   a ). 
         FIGS. 6(   a ) and  6 ( b ) are schematic cross sections for illustrating one example of a method for fabricating one example of a solar cell module in accordance with the present invention. 
         FIGS. 7(   a ) and  7 ( b ) are schematic cross sections for illustrating another example of the method for fabricating one example of the solar cell module in accordance with the present invention. 
         FIG. 8  is a schematic cross section for illustrating a method for fabricating a solar cell module employing a wiring sheet. 
         FIG. 9  is a schematic view of a wiring sheet with back electrode type solar cells disposed thereon, as seen at a side provided with the cells. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinafter, the present invention will be described in embodiments. In the figures, identical reference characters denote identical or corresponding components. 
     Wiring Sheet 
       FIG. 1(   a ) is a schematic plan view of one example of a wiring sheet in accordance with the present invention, as seen at a side thereof provided with wiring. As shown in  FIG. 1(   a ), a wiring sheet  10  includes an insulating base material  11 , and a wiring  16  including a wiring for n type  12 , a wiring for p type  13  and a wiring for connection  14 . 
     Note that the wiring for n type  12 , the wiring for p type  13  and the wiring for connection  14  are all conductive, and the wiring for n type  12  and the wiring for p type  13  are each provided in the form of a comb and the wiring for connection  14  in the form of a strip. Furthermore, except for a wiring for n type  12   a  and a wiring for p type  13   b  located at an end of wiring sheet  10 , adjacent wirings for n and p types  12  and  13  are electrically connected by the wiring for connection  14 . 
     Furthermore, wiring sheet  10  has the wiring for n type  12  and the wiring for p type  13  disposed such that the comb-like wirings for n and p types  12  and  13  have their respective teeth alternating with each other, one by one. As a result, the comb-like wirings for n and p types  12  and  13  will have their respective teeth alternating with each other, one by one, with a predetermined distance therebetween. 
     Wiring sheet  10  thus includes a comb-like portion of the wiring for n type  12  and that of the wiring for p type  13  to correspond to a cell mounting portion provided with a respective, single back electrode type solar cell. Wiring sheet  10  as a whole has a plurality of sets of such comb-like portions. Each comb-like portion has a plurality of teeth connected together by the wiring for connection  14 , i.e., the wiring for connection  14  corresponds to a connection portion connecting the plurality of teeth. 
       FIG. 1(   b ) is a schematic cross section taken along a line B-B shown in  FIG. 1(   a ). As shown in  FIG. 1(   b ), for wiring sheet  10 , the wiring for n type  12  and the wiring for p type  13  are provided only on one surface of insulating base material  11 . 
     The present wiring sheet has a plane including a cell mounting portion provided with a back electrode type solar cell and is provided with an insulation layer at this plane on a surface of at least a portion of a region excluding the cell mounting portion, and the insulation layer extends to cover at least a portion of a peripheral region of the cell mounting portion, which means that, as shown in  FIG. 4(   b ) and  FIG. 5(   a ), an insulation layer  101  is partially sandwiched between cell  20  and wiring sheet  10 . The cell thus has a peripheral portion insulated from the wiring sheet by the insulation layer, and if the cell is flexed or the wiring sheet is deformed or the like and accordingly the cell has a peripheral portion brought into contact with the wiring sheet, the insulation layer prevents such contact and can thus reduce/prevent unwanted contact between the back electrode type solar cell and the wiring sheet. 
     The present wiring sheet preferably has a plurality of cell mounting portions, and the insulation layer is provided at a portion sandwiched between adjacent cell mounting portions and located at a cell mounting side. In other words, the wiring sheet is characterized in that when a solar cell with a wiring sheet or a solar cell module is fabricated, an insulation layer is provided at a portion sandwiched between adjacent cell mounting portions and located at a cell mounting side. The portion between adjacent cell mounting portions is located on the wiring sheet between cell mounting portions provided with back electrode type solar cells, e.g., portions  10   b ,  10   b   1 ,  10   b   2  on wiring sheet  10  between adjacent cell mounting portions, as shown in  FIGS. 1 ,  4  and  5 . In other words, it can be said that a portion between adjacent cell mounting portions includes that which does not overlap a cell, as seen in a direction vertical to the cell&#39;s major surface (or the wiring sheet&#39;s major surface). In the present invention, wiring sheet  10  has an insulation layer at portions  10   b   1 ,  10   b   2  of the wiring sheet sandwiched between cell mounting portions and also closer to the cell, e.g., insulation layer  101  as shown in  FIGS. 4 and 5 . 
     In the  FIG. 4(   b ) configuration, insulation layer  101  is provided in a direction in which the wirings  12  and  13  teeth extend (i.e., in the vertical direction in  FIG. 1(   a ) and  FIG. 4(   a )) along an end of a tooth that is located at an end of a set of comb-like forms on a surface of insulating base material  11  located at portion  10   b   2  sandwiched between adjacent cell mounting portions and located at a cell mounting side. As shown in  FIG. 4(   b ), insulation layer  101  can prevent wiring sheet  10  and back electrode type solar cell  20  from misalignment in a direction orthogonal to that in which the comb-like forms of wirings  12  and  13  extend. While  FIG. 4(   b ) shows insulation layer  101  larger in thickness than wirings  12  and  13 , insulation layer  101  may not be larger in thickness than wirings  12  and  13 . The latter case also allows the insulation layer to prevent unwanted contact caused between a back electrode type solar cell and the wiring sheet. 
     Furthermore, in the  FIG. 5  configuration, insulation layer  101  is provided on a surface of wirings  12  and  13  located at portion  10   b   1  sandwiched between adjacent cell mounting portions and located at the cell mounting side, and extends along that end of the wiring for connection  14  closer to the teeth of wirings  12  and  13 . Insulation layer  101  is provided in a region including a portion at which the teeth of wirings  12  and  13  are connected to the wiring for connection  14 . This can reduce/prevent unwanted contact caused between a back electrode type solar cell and the wiring sheet if the wiring sheet is thermally deformed by a difference between the coefficient of thermal expansion of an insulating material forming the wiring sheet and the coefficient of thermal expansion of a wiring, as will be described hereinafter. Insulation layer  101  has an end on a region extending from an end of the wiring for connection  14  to the tip of the teeth opposite to the end of the wiring for connection  14  (e.g., a region  10   e  in  FIG. 1 ). As shown in  FIG. 5 , insulation layer  101  can prevent wiring sheet  10  and back electrode type solar cell  20  from misalignment in a direction orthogonal to that in which the comb-like forms of wirings  12  and  13  extend. 
     Note that  FIGS. 4 and 5  show a stage in which back electrode type solar cells  20  are bonded to the wiring sheet, and show insulation layer  101  provided, as seen in a side view. In  FIGS. 4 and 5 , the cell mounting portion corresponds to a portion at which the wiring sheet and back electrode type solar cell  20  are bonded together. 
     The insulation layer may be formed any material that provides electrical insulation, and may be formed of a variety of known insulating materials. The insulation layer can be provided in a variety of known methods, for example by attaching an insulating member in the form of tape or applying a resin composition that contains epoxy resin, acrylic resin or the like and a curing agent on the cell mounting side between adjacent cell mounting portions via a dispenser, by stamping (or transfer), or by screen-printing, ink jet or the like, and heating or exposing the resin composition to light or the like to set it to provide the insulation layer. The insulation layer may alternatively be provided by slit-coating, spraying, dipping or the like or by subjecting a wiring to blacking processing, an alumite treatment or similar surface processing to serve as an insulation film. The insulation film is provided at a desired position by means of providing the insulation film selectively only at the desired position as well as providing the insulation film in an area that includes the desired position and subsequently removing the unnecessary portion. The insulation layer may be provided before or after the wiring sheet is bonded to back electrode type solar cells. 
     The insulation layer may have a surface similar in color to the back electrode type solar cell&#39;s photoreceptive surface. This allows the back electrode type solar cell to have a less noticeable contour and a solar cell module of a design allowing the cell to be less noticeable in geometry can be fabricated. 
     Furthermore, the insulation layer may have a white surface. This allows the light incident on a region without a back electrode type solar cell to be reflected and incident on a neighboring back electrode type solar cell, and thus allows a solar cell module to generate electric power more efficiently. Note that the insulation layer may not be white and may have a hue that can reflect the light of a waveform that the back electrode type solar cell can absorb. It is a matter of course that the insulation layer may not be colored and instead be transparent. 
     The insulation layer may have a surface colored such that the insulation layer is formed of a material per se colored as desired or the insulation layer may underlie a film having a color as desired, or furthermore, the insulation layer may have a surface patterned using two or more types of colors to positively form a design of a solar cell module. 
     It is preferable to consider the color of the surface of the insulation layer, the position thereof, and the like so that coloring the surface of the insulation layer may not cause inconvenience in a process for fabricating and installing a solar cell module. For example, if the wiring sheet is provided with a marking for registration in setting back electrode type solar cells on the wiring sheet, then, it is preferable that the insulation layer is transparent, absent or the like on the marking and thus does not make the marking unrecognizable. 
     Note that insulating base material  11  may be formed of any material that is electrically insulating, and it may be formed for example of a material including at least one type of resin selected from the group consisting of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyphenylene sulfide (PPS), polyvinyl fluoride (PVF), and polyimide. 
     Furthermore, insulating base material  11  may not be limited to any particular value in thickness, and may for example be 25-150 μm. 
     Note that insulating base material  11  may be formed of a single layer, i.e., have a monolayer structure, or may be formed of two or more layers, i.e., have a multilayer structure. 
     Furthermore, wiring  16  may be formed of any material that is electrically conductive, e.g., metal including at least one type selected from the group consisting of copper, aluminum and silver. 
     Furthermore, wiring  16  is also not limited in thickness, and may for example be 15-50 μm. 
     Furthermore, it is also not needless to say that wiring  16  is also not limited in geometry to that aforementioned and may be set as appropriate. 
     Furthermore, wiring  16  may have a surface having at least a portion provided for example with an electrically conductive substance including at least one type selected from the group consisting of nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), tin (Sn), indium (In), SnPb solder, SnBi solder, and indium tin oxide (ITO). This provides a tendency that the wiring sheet  10  wiring  16  and a back electrode type solar cell&#39;s electrode as will be described later can be electrically connected satisfactorily and wiring  16  can be enhanced in weather resistance. 
     Furthermore, wiring  16  may have a surface having at least a portion subjected to blacking processing, rust-proofing, or similar surface processing. 
     Note that wiring  16  may also be formed of a single layer, i.e., have a monolayer structure, or may be formed of two or more layers, i.e., have a multilayer structure. Hereinafter will be described one example of a method of fabricating wiring sheet  10  in the configuration shown in  FIG. 1(   a ) and  FIG. 1(   b ). 
     Initially, insulating base material  11  for example of PET film is prepared and an electrically conductive substance for example in the form of metal foil, metal plate or the like is stuck across one surface of insulating base material  11 . 
     Subsequently, the electrically conductive substance affixed on one surface of insulating base material  11  is partially, photolithographically or similarly etched away and thus patterned to provide on the surface of insulating base material  11  with wiring  16  including the wiring for n type  12 , the wiring for p type  13 , the wiring for connection  14  and the like formed of the patterned electrically conductive substance. 
     Wiring sheet  10  configured as shown in  FIG. 1(   a ) and  FIG. 1(   b ) can thus be produced. 
     Wiring sheet  10  is provided with insulation layer  101  at portion  10   b  between cell mounting portions, as follows: after the  FIGS. 1(   a ) and  1 ( b ) configuration is provided, for example a screen method or a similar printing method is employed to deposit and set an insulating resin material at the cell mounting side on the wirings  12  and  13  of wiring sheet  10  and insulating base material  11  at a portion located at portion  10   b  sandwiched between cell mounting portions to provide insulation layer  101 . 
     Back Electrode Type Solar Cell 
       FIG. 2(   a ) is a schematic cross section of one example of a back electrode type solar cell electrically connected to a wiring of a wiring sheet in accordance with the present invention.  FIG. 2(   a ) shows back electrode type solar cell  20  for example having an n or p type silicon or similar semiconductor substrate  21 , an antireflection film  27  provided on an uneven surface of semiconductor substrate  21  serving as a photoreceptive surface of back electrode type solar cell  20 , and a passivasion film  26  provided on a back surface of semiconductor substrate  21  serving as a back surface of back electrode type solar cell  20 . 
     Furthermore, semiconductor substrate  21  at the back surface has for example phosphorus or a similar n type impurity and boron or a similar p type impurity diffused therein to have an n type impurity diffusion region  22  and a p type impurity diffusion region  23 , respectively, alternately with a predetermined distance therebetween, and is also provided with an electrode for n type  24  and an electrode for p type  25  in contact with n type impurity diffusion region  22  and p type impurity diffusion region  23 , respectively, via a contact hole provided through passivasion film  26  provided on the back surface of semiconductor substrate  21 . 
     Herein, The semiconductor substrate  21  back surface of n or p type conduction will have a plurality of pn junctions formed at an interface of n type impurity diffusion region  22  or p type impurity diffusion region  23  and an internal portion of semiconductor substrate  21 . Whichever of n type conduction or p type conduction semiconductor substrate  21  may be of, n type impurity diffusion region  22  and p type impurity diffusion region  23  have junction with an internal portion of semiconductor substrate  21  and accordingly the electrode for n type  24  and the electrode for p type  25  will be electrodes corresponding respectively to the plurality of pn junctions provided at the back surface of semiconductor substrate  21 . 
       FIG. 2(   b ) is a schematic plan view of one example of a back surface of semiconductor substrate  21  of back electrode type solar cell  20  shown in  FIG. 2(   a ). Herein, as shown in  FIG. 2(   b ), the electrode for n type  24  and the electrode for p type  25  are each in the form of a comb and disposed such that the comb-like electrodes for n and p types  24  and  25  have their respective teeth meshed one by one alternately. As a result, the comb-like electrodes for n and p types  24  and  25  have their respective teeth alternately one by one with a predetermined distance interposed. 
     Herein, the electrode for n type  24  and the electrode for p type  25  provided at the back surface of back electrode type solar cell  20  may have a shape and a position different than  FIG. 2(   b ): they may have any shape and position allowing electrical connection to the wiring sheet  10  wirings for n and p types  12  and  13 , respectively. 
       FIG. 3(   a ) is a schematic plan view of another example of the back surface of semiconductor substrate  21  of back electrode type solar cell  20  shown in  FIG. 2(   a ). As shown in  FIG. 3(   a ), the electrode for n type  24  and the electrode for p type  25  are each formed in a strip extending in the same direction (i.e., the upward/downward direction as seen in  FIG. 3(   a )) and are alternately disposed, one by one, on the back surface of semiconductor substrate  21  in a direction orthogonal to that in which they extend. 
       FIG. 3(   b ) is a schematic plan view of still another example of the back surface of semiconductor substrate  21  of back electrode type solar cell  20  shown in  FIG. 2(   a ). As shown in  FIG. 3(   b ), the electrode for n type  24  and the electrode for p type  25  are each formed in a dot, and a row of dot electrodes for n type  24  (extending upward/downward as seen in  FIG. 3(   b )) and a row of dot electrodes for p type  25  (extending upward/downward as seen in  FIG. 3(   b )) are disposed on the back surface of semiconductor substrate  21  alternately. 
     Furthermore, back electrode type solar cell  20  may have the electrode for n type  24  and/or the electrode for p type  25  with at least a portion thereof having a surface provided for example with an electrically conductive substance including at least one type selected from the group consisting of nickel (Ni), gold (Au), platinum (Pt), palladium (Pd), silver (Ag), tin (Sn), indium (In), SnPb solder, SnBi solder, and indium tin oxide (ITO). This provides a tendency that the wiring sheet  10  wiring  16  and the back electrode type solar cell  20  electrodes (the electrode for n type  24  and the electrode for p type  25 ) can be electrically connected satisfactorily and the back electrode type solar cell  20  electrodes (the electrode for n type  24  and the electrode for p type  25 ) can be enhanced in weather resistance. 
     Furthermore, back electrode type solar cell  20  may have the electrode for n type  24  and/or the electrode for p type  25  with at least a portion thereof having a surface subjected for example to blacking processing, rust-proofing, or similar surface processing. 
     Semiconductor substrate  21  can be implemented for example as an n or p type polycrystalline or monocrystalline or similar silicon substrate or the like. 
     The electrode for n type  24  and the electrode for p type  25  can be implemented for example as electrodes formed of metal such as silver. 
     Passivasion film  26  can be implemented for example as silicon oxide film, silicon nitride film, or silicon oxide film and silicon nitride film stacked in layers, or the like. 
     Antireflection film  27  can be implemented for example as silicon nitride film or the like. 
     Note that the concept of the present back electrode type solar cell includes not only a back electrode type solar cell having a semiconductor substrate with only one surface (a back surface) having both an electrode for p type and an electrode for n type, but also a metal wrap through (MWT) cell (i.e., a solar cell having a semiconductor substrate having a through hole receiving a portion of an electrode therein) or a similar, so called back electrode type solar cell (i.e., a solar cell extracting an electric current from a semiconductor substrate&#39;s back surface opposite to the semiconductor substrate&#39;s photoreceptive surface) or a similar solar cell having an electrode for p type and an electrode for n type both connected to a wiring at one surface side. 
     Solar Cell with Wiring Sheet 
       FIG. 4(   a ) is a schematic plan view of one example of a solar cell with a wiring sheet in accordance with the present invention, as seen at its photoreceptive surface, and  FIG. 4(   b ) is a schematic cross section taken along a line B-B indicated in  FIG. 4(   a ). In the following description, the present invention provides a solar cell with a wiring sheet in one example such that the  FIGS. 1(   a ) and  1 ( b ) wiring sheet  10  has a surface with wiring  16  thereon, with a plurality of back electrode type solar cells  20  shown in  FIG. 2(   a ) and  FIG. 2(   b ) electrically connected thereto. The solar cell with the wiring sheet in accordance with the present invention, however, is not limited in configuration to that shown in  FIG. 4(   a ) and  FIG. 4(   b ). 
     As shown in  FIG. 4(   a ) and  FIG. 4(   b ), the present invention provides a solar cell with a wiring sheet, that is configured such that back electrode type solar cell  20  is disposed on wiring sheet  10  such that the back electrode type solar cell  20  back surface and the wiring sheet  10  side provided with wiring  16  face each other. 
     More specifically, as shown in  FIG. 4(   b ), the electrode for n type  24  at the back surface of back electrode type solar cell  20  is bonded to the wiring for n type  12  provided on a surface of insulating base material  11 , and the electrode for p type  25  at the back surface of back electrode type solar cell  20  is bonded to the wiring for p type  13  provided on the surface of insulating base material  11 . Thus the back electrode type solar cell  20  electrode for n type  24  and the wiring sheet  10  wiring for n type  12  are electrically connected together and so are the back electrode type solar cell  20  electrode for p type  25  and the wiring sheet  10  wiring for p type  13 . Note that in  FIG. 4  the cell mounting portion corresponds to a portion at which wiring sheet  10  and back electrode type solar cell  20  are bonded together. 
     As shown in  FIG. 1(   a ), except for the wiring for n type  12   a  and the wiring for p type  13   a  each located at an end of wiring sheet  10 , adjacent wirings for n and p types  12  and  13  are electrically connected together by the wiring for connection  14  and hence back electrode type solar cells  20  mounted on wiring sheet  10  adjacently will be electrically connected to each other. Accordingly, the  FIG. 4(   a ) and  FIG. 4(   b ) configuration provides solar cells with a wiring sheet such that wiring sheet  10  has back electrode type solar cells  20  mounted thereon all electrically connected in series. 
     A solar cell, or back electrode type solar cell  20 , with a wiring sheet receives light at the photoreceptive surface, and thereby generates an electric current, which is in turn extracted through the back electrode type solar cell  20  electrodes for n and p types  24  and  25  to the wiring sheet  10  wirings for n and p types  12  and  13 . The wiring sheet  10  wirings for n and p types  12  and  13  receive the electric current, which is in turn extracted outside the solar cell with the wiring sheet through the wirings for n and p types  12   a  and  13   a  each located at an end of wiring sheet  10 . 
     Furthermore, the solar cell with the wiring sheet as described above may be provided for example as shown in  FIG. 4(   b ): curing resin  17  may be introduced between the back electrode type solar cell  20  semiconductor substrate  21  and the wiring sheet  10  insulating base material  11  at a region between the back electrode type solar cell  20  adjacent electrodes for n and p types  24  and  25  to bond back electrode type solar cell  20  and insulating base material  11  more firmly. While  FIG. 4(   b ) shows insulation layer  101  in contact with wirings  12  and  13 , curing resin  17  may be posed between insulation layer  101  and wirings  12  and  13 . 
     The present invention provides a solar cell with a wiring sheet, that is characterized in that the wiring sheet has a plane including a cell mounting portion provided with a back electrode type solar cell and is provided with an insulation layer at this plane on a surface of at least a portion of a region excluding the cell mounting portion, and the insulation layer extends to cover at least a portion of a peripheral region of the cell mounting portion (i.e., as shown in  FIG. 4(   b ) and  FIG. 5(   a ), insulation layer  101  is partially sandwiched between cell  20  and wiring sheet  10 ). The cell can thus have a peripheral portion insulated by the insulation layer and if the cell flexes or the wiring sheet is deformed or the like and the cell&#39;s peripheral portion is brought into contact with the wiring sheet the insulation layer prevents such contact and can thus reduce/prevent unwanted contact caused between the back electrode type solar cell and a wiring of the wiring sheet. 
     Furthermore, the solar cell with the wiring sheet in accordance with the present invention is characterized in that the wiring sheet is provided with an insulation layer at the cell mounting side of a portion of the wiring sheet that is sandwiched between adjacent cell mounting portions. The portion between adjacent cell mounting portions is as has been described above, and for example, as shown in  FIG. 4(   a ), wiring sheet  10  is provided with insulation layer  101  at portion  10   b  sandwiched between back electrode type solar cell  20  mounting portions and located at the cell mounting side. Note that herein a solar cell mounting portion is a region of wiring sheet  10  that is provided with solar cell  20  of  FIG. 4 , as shown in  FIG. 1(   a ) by cell mounting portion  10   a,  a region of wiring sheet  10  that is provided with solar cell  20 , as shown in  FIG. 5  by cell mounting portion  10   a , and the like. 
     In the  FIG. 4(   b ) configuration, insulation layer  101  is provided in a direction in which the teeth of wirings  12  and  13  extend (i.e., in the vertical direction in  FIG. 1(   a ) and  FIG. 4(   a )) along an end of a tooth that is located at an end of a set of comb-like forms on a surface of insulating base material  11  located at portion  10   b   2  sandwiched between adjacent cell mounting portions and located at a cell mounting side. As shown in  FIG. 4(   b ), insulation layer  101  can prevent wiring sheet  10  and back electrode type solar cell  20  from misalignment in a direction orthogonal to that in which the comb-like forms of wirings  12  and  13  extend. While  FIG. 4(   b ) shows insulation layer  101  larger in thickness than wirings  12  and  13 , insulation layer  101  may not be larger in thickness than wirings  12  and  13 . The latter case also allows the insulation layer to prevent unwanted contact caused between a back electrode type solar cell and the wiring sheet. 
     The insulation layer may have a surface similar in color to the back electrode type solar cell&#39;s photoreceptive surface. This allows the back electrode type solar cell to have a less noticeable contour and a solar cell module of a design allowing the cell to be less noticeable in geometry can be fabricated. 
     Furthermore, the insulation layer may have a white surface. This allows the light incident on a region without a back electrode type solar cell to be reflected and incident on a neighboring back electrode type solar cell, and thus allows a solar cell module to generate electric power more efficiently. Note that the insulation layer may not be white and may have a hue that can reflect the light of a waveform that the back electrode type solar cell can absorb. It is a matter of course that the insulation layer may not be colored and instead be transparent. 
     The insulation layer may have a surface colored such that the insulation layer is formed of a material per se colored as desired or the insulation layer may underlie a film having a color as desired, or furthermore, the insulation layer may have a surface patterned using two or more types of colors to positively form a design of a solar cell module. 
     It is preferable to consider the color of the surface of the insulation layer, the position thereof, and the like so that coloring the surface of the insulation layer may not cause inconvenience in a process for fabricating and installing a solar cell module. For example, if the wiring sheet is provided with a marking for registration in setting back electrode type solar cells on the wiring sheet, then, it is preferable that the insulation layer is transparent, absent or the like on the marking and thus does not make the marking unrecognizable. 
       FIG. 5(   a ) is a schematic cross section of an example of a solar cell with a wiring sheet in accordance with the present invention, taken along a line A-A indicated in  FIG. 4(   a ). While, as shown in the figure, it is preferable that wiring sheet  10  is provided with insulation layer  101  on that side of the wiring for connection  14  (see  FIG. 1)  located at portion  10   b   1  sandwiched between cell mounting portions (see  FIG. 4(   a ),  FIG. 5(   a )) which is closer to back electrode type solar cell  20 , wiring sheet  10  may be provided with insulation layer  101  at portion  10   b   2  between cell mounting portions that does not have any wiring of wiring sheet  10  (see  FIGS. 4(   a ),  4 ( b )). This configuration effectively reduces/prevents not only contact between cells but also that between a cell and a wiring, and hence insufficient insulation, electrical leakage and short circuit attributed thereto. 
     Furthermore, as shown in  FIG. 5(   b ), wiring sheet  10  may have a bent portion  10   c  at the wiring for connection  14  (see  FIG. 1)  located at portion  10   b   1  sandwiched between cell mounting portions (see ( FIG. 4(   a ),  FIG. 5(   a )), and may be provided at the cell mounting side of bent portion  10   c  with insulation layer  101 . In the  FIG. 5(   b ) configuration, by bent portion  10   c , wiring sheet  10 , as seen in the direction of the thickness of back electrode type solar cell  20  or the wiring sheet, has at least a portion of the portion with insulation layer  101 , deformed to be closer to back electrode type solar cell  20  than that portion of wiring sheet  10  which does not have insulation layer  101 . This deformation can be caused when wiring sheet  10  and a back electrode type solar cell are bonded together through a heat treatment, as done in a method for fabricating a solar cell with a wiring sheet, as will be described hereinafter. Furthermore, this deformation can also be caused when a solar cell module is sealed in a step involving a heat treatment, as will be described hereinafter. 
     Hereinafter, how the wiring sheet is thermally deformed will be described. The wiring sheet is configured of an insulating base material and a wiring, which are formed of different materials, respectively, and have different coefficients of thermal expansion, respectively. As such, the wiring sheet at a portion with the insulating base material underlying the wiring will be distorted as temperature varies. Furthermore, the insulating base material is typically implemented as a sheet of a resin material, and when such a resin sheet is heated it can contract, i.e., the resin sheet can thermally contract. On the other hand, the wiring is typically implemented as metal foil, which, when heated, once thermally expands, and thereafter when it is cooled it may not recover its initial dimension. The insulating base material and the wiring thus have such different thermal characteristics, and accordingly, the wiring sheet is thermally deformed. 
     Furthermore, the wiring sheet&#39;s distortion caused between the insulating base material and the wiring as their materials and hence coefficients of thermal expansion are different is caused whenever the wiring sheet&#39;s temperature rises/falls, and accordingly, a solar cell module installed outdoor is repeatedly distorted as solar irradiation, climate and the like and hence temperature vary. This distortion becomes stress exerted to the wiring and may break it. 
     If such thermal deformation is absent, a form as shown in  FIG. 5(   a ) is provided, whereas when such thermal deformation is caused, a form as shown in  FIG. 5(   b ) may be provided. In the  FIG. 5(   b ) case, bent portion  10   c  causes a wiring of wiring sheet  10  located at portion  10   b  sandwiched between cell mounting portions to approach back electrode type solar cell  20 , and if the deformation is significant, the wiring of wiring sheet  10  may be brought into contact with a portion other than an electrode of back electrode type solar cell  20 , resulting in unsatisfactory insulation, electrical leakage, and short circuit. 
     Accordingly, as shown in  FIG. 5(   b ), wiring sheet  10  is provided with insulation layer  101  on the cell mounting side surface of a wiring located at portion  10   b  sandwiched between cell mounting portions, so that wiring sheet  10  can be prevented from having the wiring brought into contact with a portion other than an electrode of back electrode type solar cell  20 . Thus such a configuration as described above effectively prevents the wiring sheet from having a cell and a wiring brought into contact with each other, and hence unsatisfactory insulation, electrical short circuit, and cracking of the cell. 
     Furthermore in the  FIGS. 5(   a ) and  5 ( b ) configuration it is preferable that insulation layer  101  be provided in a region including a portion at which the teeth of wirings  12  and  13  are connected to the wiring for connection  14 . The teeth of wirings  12  and  13  and the wiring for connection  14  are connected together as shown in  FIG. 1 , and the wirings  12  and  13  teeth, which are small in width, extend from one side of wiring  14 , which has a relatively large area. When the wiring sheet having a wiring of such a geometry mounted on an insulating base material has the wiring subjected to a stress by such distortion caused between the insulating base material and the wiring, as described above, the teeth of wirings  12  and  13  are significantly deformed lengthwise, whereas the wiring  14 , having a relatively large area, is less misaligned from the insulating base material, and accordingly, the stress is concentrated at the connection portion of the teeth of wirings  12  and  13  and the wiring for connection  14 , and the wiring is thus breakable. Insulation layer  101  provided at the connection portion of the teeth of wirings  12  and  13  and the wiring for connection  14  can reinforce the wirings and thus prevent stress concentration, and hence the wirings from breakage. 
     Furthermore, in the  FIGS. 5(   a ) and  5 ( b ) configuration, insulation layer  101  is provided on that surface of wirings  12  and  13  located at portion  10   b   1  sandwiched between adjacent cell mounting portions which is located at the cell mounting side such that insulation layer  101  is provided along that end of wiring for connection  14  closer the comb-like portions of wirings  12  and  13 , and insulation layer  101  has an end on a region extending from an end of the wiring for connection  14  to an end of the teeth opposite to that end of the wiring for connection  14 . As shown in  FIGS. 5(   a ) and  5 ( b ), such insulation layer  101  can reduce/prevent misalignment between wiring sheet  10  and back electrode type solar cell  20  in a direction in which the wirings  12  and  13  comb-like portions extend (i.e., the vertical direction as seen in  FIG. 1(   a ) and  FIG. 4(   a )). 
     Reference will now be made to  FIG. 9  to more specifically describe how to reduce/prevent misalignment of the comb-like portions of wirings  12  and  13  in the direction in which they extend. 
     As shown in  FIG. 9 , when electrodes  24 ,  25  are normally aligned, as shown at a normally connected cell  20   a , no short circuit or the like is caused, whereas when electrodes  24 ,  25  are misaligned in the direction in which wiring  16  extends, as shown at a defective cell  20   b , a short circuit will be caused at a short circuit portion  16   a . Note that  FIG. 9  shows wiring sheet  10  with back electrode type solar cell  20  mounted thereon, as seen at the cell&#39;s side, and to help to understand the positional relationship between wirings  12  and  13  and electrodes  24 ,  25 , the semiconductor substrate of back electrode type solar cell  20  is indicated only by its periphery, as indicated by a dotted line. 
     This problem can be handled by providing insulation layer  101  as shown in  FIGS. 5(   a ) and  5 ( b ) to reduce/prevent misalignment between wiring sheet  10  and back electrode type solar cell  20  causing such short circuit by initial misalignment or the like. This allows a cell to have an electrode provided in a vicinity of an end of the cell and wirings to be spaced by a reduced distance without providing a defective wiring, and a solar cell with a wiring sheet can be fabricated efficiently. 
     Preferably, the  FIG. 9  solar cell with a wiring sheet has wiring sheet  10  provided with insulation layer  101  covering a region of back electrode type solar cell  20  outer than a group of electrodes  24 ,  25 . This can prevent unwanted contact caused between the region of the back electrode type solar cell outer than the group of the electrodes and a wiring of the wiring sheet. 
     Note that in this example preferably insulation layer  101  has an end within a spacing  16   b  shown in  FIG. 9 , since this can prevent back electrode type solar cell  20  from having electrodes  24 ,  25  brought into contact with the wiring for connection  14  and can prevent back electrode type solar cell  20  and wiring sheet  10  from having electrodes  24 ,  25  and wirings  12  and  13 , respectively, in contact with each other over a reduced area. 
     Method for Fabricating Solar Cell with Wiring Sheet 
     In the above described configuration, the back electrode type solar cell  20  electrode for n type  24  and the wiring sheet  10  wiring for n type  12  may be bonded together in any method, and so may the back electrode type solar cell  20  electrode for p type  25  and the wiring sheet  10  wiring for p type  13 , and for example they can be bonded together with at least one type of adhesive selected from the group consisting of solder, electrically conductive adhesive, anisotropic conductive film (ACF), anisotropic conductive paste (ACPA), and non conductive paste (NCP). Furthermore, rather than the above adhesives, a sealing material described hereinafter may be used to bond them together. 
     For example, at least one type of adhesive selected from the group consisting of solder, electrically conductive adhesive, anisotropic conductive film, anisotropic conductive paste, and non conductive paste is applied to a surface of at least one of wiring sheet  10  and back electrode type solar cell  20  and subsequently back electrode type solar cell  20  is disposed on wiring sheet  10  such that the electrode for n type  24  and the wiring for n type  12  are electrically connected together and so are the electrode for p type  25  and the wiring for p type  13 . 
     Then, for example, wiring sheet  10  and back electrode type solar cell  20  are pressed together and in that condition undergo a heat treatment or the like to utilize the adhesive&#39;s adhesive strength to bond wiring sheet  10  and back electrode type solar cell  20  together. Thus the back electrode type solar cell  20  electrode for n type  24  and the wiring sheet  10  wiring for n type  12  are fixed and bonded together while they are electrically connected together, and so are the back electrode type solar cell  20  electrode for p type  25  and the wiring sheet  10  wiring for p type  13 . 
     Furthermore, it is needless to say that the above solder, electrically conductive adhesive, anisotropic conductive film, anisotropic conductive paste and other similar electrically conductive adhesive can be applied at a position at which short circuit is not caused in the solar cell with the wiring sheet. 
     Furthermore, it is needless to say that the above electrically insulating adhesive or a similarly electrically insulating adhesive can be applied at a position that does not prevent electrical conduction of the solar cell with the wiring sheet. 
     Note that the idea of the solar cell with the wiring sheet in accordance with the present invention includes not only that with wiring sheet  10  having a surface with a plurality of back electrode type solar cells  20  thereon electrically connected together in a line but also that with a plurality of back electrode type solar cells  20  electrically connected together in a form other than a line, e.g., in a matrix, as shown in  FIG. 4(   a ). 
     If the solar cell with the wiring sheet in accordance with the present invention is fabricated in a method using solder or thermosetting resin as an adhesive, a heat treatment will be performed to connect the solder or set the resin. Furthermore, if the adhesive is ultraviolet curing resin, a heat treatment will be performed to further cure the adhesive of the ultraviolet curing resin. 
     When wiring sheet  10  and back electrode type solar cell  20  are bonded through a heat treatment, then, as has been described previously, wiring sheet  10  may deform, for example as shown in  FIG. 5(   b ). However, wiring sheet  10 , having insulation layer  101  on the cell mounting side surface of a wiring located at portion  10   b  sandwiched between cell mounting portions of the wiring sheet, can be prevented from having the wiring brought into contact with a portion of back electrode type solar cell  20  other than an electrode. 
     Furthermore, the wiring sheet&#39;s thermal contraction/expansion can cause misalignment between the wiring sheet and the back electrode type solar cell. However, as has been described previously, the wiring sheet that has an insulation layer on a surface of a wiring located between cell mounting portions of the wiring sheet that is located at the cell mounting side and an insulation layer on a surface of an insulating substrate located between cell mounting portions of the wiring sheet that is located at the cell mounting side, can reduce/prevent short circuit of the wiring of the wiring sheet and that of the back electrode type solar cell. 
     Solar Cell Module 
       FIGS. 6(   a ) and  6 ( b ) are schematic cross sections each for illustrating one example of a method for fabricating one example of a solar cell module in accordance with the present invention. Hereinafter reference will be made to  FIG. 6(   a ) and  FIG. 6(   b ) to describe one example of the method for fabricating one example of a solar cell module in accordance with the present invention. 
     While the following will describe as one example of the present solar cell module a solar cell module having sealed in a sealing material a solar cell with a wiring sheet shown in the  FIG. 4(   a ) and  FIG. 4(   b ) configuration, the present solar cell module&#39;s configuration is not limited thereto. 
     Initially, as shown in  FIG. 6(   a ), a transparent substrate  30  with first transparent resin  31   a  is positioned closer to the solar cell with the wiring sheet configured as shown in  FIG. 4(   a ) and  FIG. 4(   b ), and a back surface protection sheet  32  with second transparent resin  31   b  is positioned closer to the wiring sheet of the solar cell with the wiring sheet configured as shown in  FIG. 4(   a ) and  FIG. 4(   b ). 
     Then, first transparent resin  31   a  is pressed into contact with a back electrode type solar cell of the solar cell with the wiring sheet and second transparent resin  31   b  is pressed into contact with the wiring sheet of the solar cell with the wiring sheet and they thus undergo a heat treatment to set first transparent resin  31   a  and second transparent resin  31   b  integrally. Thus, as shown in  FIG. 6(   b ), first transparent resin  31   a  and second transparent resin  31   b  are integrated together to provide sealing material  31  sealing the solar cell with the wiring sheet and thus fabricate one example of the present solar cell module. 
     In the  FIG. 6(   b ) solar cell module, curing resin  17  provides contractile force which firmly presses the back electrode type solar cell against the wiring sheet and hence more firmly bond the back electrode type solar cell&#39;s electrode for n type  24  and the wiring sheet&#39;s wiring for n type  12  together and the back electrode type solar cell&#39;s electrode for p type  25  and the wiring sheet&#39;s wiring for p type  13  together to obtain satisfactory electrical connection between an electrode of the back electrode type solar cell and a wiring of the wiring sheet. 
     Note that the solar cell with the wiring sheet can be sealed in sealing material  31  through press and a heat treatment for example using equipment referred to as a laminator performing vacuum press and a heat treatment. 
     More specifically, for example, the laminator is employed to thermally deform first transparent resin  31   a  and second transparent resin  31   b  and thermally set first transparent resin  31   a  and second transparent resin  31   b  to integrate the transparent resins together to provide sealing material  31  to encapsulate and thus seal the solar cell with the wiring sheet therein. 
     Herein, as the intermediate product is heated, for example the resin sheet that configures the insulating base material of the wiring sheet thermally contracts and on the other hand the metal foil that configures a wiring of the wiring sheet thermally expands, and in that condition, a resin composition  17   a , first transparent resin  31   a  and the like are set and thus provide constraint and prevent recovery of an initial size. Furthermore, the wiring sheet at cell mounting portions has back electrode type solar cells, which constrain the wiring sheet and accordingly, stress concentrates between adjacent cell mounting portions, and the wiring sheet deforms such that a bent portion is formed between the adjacent cell mounting portions. 
     Such deformation can cause unwanted contact between a wiring of the wiring sheet and a back electrode type solar cell. However, as has been described previously, such a defect can be prevented by the wiring sheet having an insulation layer on the cell mounting side surface of the wiring between cell mounting portions of the wiring sheet. 
     Furthermore, the wiring sheet&#39;s thermal contraction/expansion can cause misalignment between the wiring sheet and the back electrode type solar cell. However, as has been described previously, the wiring sheet that has an insulation layer on a surface of a wiring located between cell mounting portions of the wiring sheet that is located at the cell mounting side and an insulation layer on a surface of an insulating substrate located between cell mounting portions of the wiring sheet that is located at the cell mounting side, can reduce/prevent short circuit of the wiring of the wiring sheet and that of the back electrode type solar cell. 
     Note that vacuum press means press in an atmosphere reduced in pressure and thus smaller in pressure than the atmospheric pressure. Note that herein, performing the press by vacuum press is preferable in that it provides a tendency that first transparent resin  31   a  and second transparent resin  31   b  have less voids formed therebetween and first transparent resin  31   a  and second transparent resin  31   b  integrated together, or sealing material  31 , have less air voids remaining therein. Furthermore, vacuum press also provides a tendency to be advantageous in ensuring that the back electrode type solar cell and the wiring sheet are pressed together with uniform force. 
     Note that transparent substrate  30  may be any substrate that is transparent for solar light and it can for example be a glass substrate. 
     Furthermore, first transparent resin  31   a  and second transparent resin  31   b  may be any resin that is transparent for solar light, and inter alfa, at least one type of transparent resin selected from the group consisting of ethylene vinyl acetate resin, epoxy resin, acrylic resin, urethane resin, olefin resin, polyester resin, silicone resin, polystyrene resin, polycarbonate resin and rubber resin is preferable. In that case, sealing material  31  is excellent in weather resistance and enhanced in permeability for solar light, and can be fixed to transparent substrate  30  with sufficient strength without significantly impairing the solar cell module&#39;s output (a short circuit electric current, or a current in operation, in particular). This provides a tendency ensuring that the solar cell module is reliable for a long term. 
     Note that first transparent resin  31   a  and second transparent resin  31   b  may be identical or different in type. 
     Furthermore, when the solar cell with the wiring sheet is sealed in sealing material  31  through a heat treatment and for example first transparent resin  31   a  and second transparent resin  31   b  are both ethylene vinyl acetate resin, the heat treatment can be performed to heat first transparent resin  31   a  and second transparent resin  31   b  for example to 100-200° C. 
     Furthermore, back surface protection sheet  32  can be any that can protect the back surface of sealing material  31 , and can for example be a conventionally used weatherproof film such as PET. 
     Furthermore, back surface protection sheet  32  may include metallic film for example of aluminum or the like in order to sufficiently reduce/prevent water vapor, oxygen and/or the like transmitted into sealing material  31  and thus ensure long-term reliability. 
     Furthermore, for the solar cell module&#39;s end surface, to which it is difficult to closely attach back surface protection sheet  32 , moisture-proof tape such as butyl rubber tape can be used to completely closely attach back surface protection sheet  32  thereto. 
       FIGS. 7(   a ) and  7 ( b ) are schematic cross sections for illustrating another example of the method for fabricating one example of the solar cell module in accordance with the present invention. Hereinafter reference will be made to  FIG. 7(   a ) and  FIGS. 7(   b ) to describe another example of the method for fabricating one example of the solar cell module in accordance with the present invention. While the following will also describe as one example of the present solar cell module a solar cell module having sealed in a sealing material a solar cell with a wiring sheet shown in the  FIG. 4(   a ) and  FIG. 4(   b ) configuration, the present solar cell module&#39;s configuration is not limited thereto. 
     Initially, as shown in  FIG. 7(   a ), back surface protection sheet  32  is alone disposed adjacent to the wiring sheet of the solar cell with the wiring sheet, and transparent substrate  30  with first transparent resin  31   a  is disposed adjacent to a back electrode type solar cell of the solar cell with the wiring sheet. 
     Subsequently, first transparent resin  31   a  is pressed to the back electrode type solar cell of the solar cell with the wiring sheet and in that condition undergoes a heat treatment to encapsulate and thus seal the solar cell with the wiring sheet in first transparent resin  31  a, as shown in  FIG. 7(   b ). First transparent resin  31   a  thus seals the solar cell with the wiring sheet therein and one example of the present solar cell module is thus fabricated. 
     The  FIG. 7(   b ) solar cell module also has curing resin  17  cured and thus providing contractile force which firmly presses the back electrode type solar cell against the wiring sheet and hence more firmly bond the back electrode type solar cell&#39;s electrode for n type  24  and the wiring sheet&#39;s wiring for n type  12  together and the back electrode type solar cell&#39;s electrode for p type  25  and the wiring sheet&#39;s wiring for p type  13  together to obtain satisfactory electrical connection between an electrode of the back electrode type solar cell and a wiring of the wiring sheet. 
     One example of the present solar cell module thus fabricated has a back electrode type solar cell having a photoreceptive surface to receive light to thereby generate an electric current, which is in turn extracted through the back electrode type solar cell&#39;s electrodes for n and p types  24  and  25  to the wiring sheet&#39;s wirings for n and p types  12  and  13 . The wiring sheet&#39;s wirings for n and p types  12  and  13  receive the electric current, which is in turn extracted from the wirings for n and p types  12   a  and  13   a , which are located at an end of wiring sheet  10 , as shown in  FIG. 1(   a ), and passed through a terminal electrically connected to wirings for n and p types  12   a  and  13   a , and therefrom output through back surface protection sheet  32  externally. 
     Furthermore, one example of the present solar cell module thus fabricated may have a frame for example of aluminum alloy attached to surround the solar cell module peripherally. 
     The present solar cell module is characterized in that wiring sheet  10  is provided with an insulation layer at a cell mounting side between adjacent cell mounting portions. The portion between adjacent cell mounting portions is as has been described above, and for example, as shown in  FIG. 4(   a ), wiring sheet  10  is provided with insulation layer  101  at portion  10   b  sandwiched between back electrode type solar cell  20  mounting portions and located at the cell mounting side. 
     Herein, as the intermediate product is heated to be sealed, for example the resin sheet that configures the insulating base material of the wiring sheet thermally contracts and on the other hand the metal foil that configures a wiring of the wiring sheet thermally expands, and in that condition, a resin composition  17   a , first transparent resin  31   a  and the like are set and thus provide constraint and prevent recovery of an initial size. Furthermore, the wiring sheet at cell mounting portions has back electrode type solar cells, which constrain the wiring sheet and accordingly, stress concentrates between adjacent cell mounting portions, and the wiring sheet deforms such that a bent portion is formed between the adjacent cell mounting portions. Such deformation can cause unwanted contact between a wiring of the wiring sheet and a back electrode type solar cell. However, as has been described previously, such a defect can be prevented by the wiring sheet having an insulation layer on a surface of the wiring between cell mounting portions of the wiring sheet. 
     Note that if the aforementioned wiring sheet having undergone a heat treatment and thus bonded to a back electrode type solar cell as a result has deformation, the subsequent sealing step involving a heat treatment may increase the deformation, or even if the wiring sheet having undergone the heat treatment and thus bonded to the back electrode type solar cell does not have deformation, the subsequent sealing step heats and may thus deform the wiring sheet. 
     Furthermore, the sealing step heats the wiring sheet and thus causes the wiring sheet to thermally contract/expand and thus misalign from a back electrode type solar cell. However, as has been described previously, the wiring sheet that has an insulation layer on a surface of a wiring located between cell mounting portions of the wiring sheet that is located at the cell mounting side and an insulation layer on a surface of an insulating substrate located between cell mounting portions of the wiring sheet that is located at the cell mounting side, can reduce/prevent short circuit between the wiring of the wiring sheet and the back electrode type solar cell. Furthermore, misalignment caused as the sealing material is fluidized can also be reduced/prevented by these insulation layers. 
     Note that the wiring sheet may have a portion additionally deformed and may have an existing deformation further deformed and the wiring sheet and a solar cell may have a portion additionally misaligned and may have an existing misalignment further misaligned after the solar cell module has completely been fabricated, as the environment surrounding the product varies in temperature. 
     In accordance with the present invention, a wiring sheet is provided with an insulation layer on a surface of a wiring between adjacent cell mounting portions of the wiring sheet to reduce/prevent unwanted contact between the wiring of the wiring sheet and a back electrode type solar cell, and hence unsatisfactory insulation, electrical leakage, short circuit, and cracking of the cell, and this allows cells to be spaced by a distance smaller than conventional to achieve more efficient conversion. 
     EXAMPLES  
     Example 1 
     Initially, as the wiring sheet&#39;s insulating base material, a PET film of 510 mm in width, 400 mm in length and 50 μm in thickness was prepared. Then, copper foil of 35 μm in thickness was affixed throughout one surface of the PET film. More specifically, an adhesive was applied to one surface of the PET film and copper foil was superposed thereon, and they were pressurized and heated and thus bonded together. 
     Then, the copper foil on the surface of the PET film was partially etched and thus patterned in a form as shown in  FIG. 1(   a ) to form wiring  16  including a comb-like wiring for n type  12 , a comb-like wiring for p type  13 , and a wiring for connection  14  in the form of a strip electrically connecting the wiring for n type  12  and the wiring for p type  13  together. Simultaneously, the wiring for connection  14  (see  FIG. 1)  was provided with five holes per a length of 125 mm so as to be parallel to solar cells at portion  10   b   1  (see  FIG. 1(   a ),  FIG. 4(   a ), and  FIG. 5(   a )) between adjacent cell mounting portions of wiring sheet  10  when the wiring sheet is produced as a solar cell with a wiring sheet or a solar cell module. This hole was provided so that the wiring sheet&#39;s thermal deformation causes bent portion  10   e  as shown in  FIG. 5(   b ). 
     Then, insulation film was attached throughout a surface of the wiring for connection  14  in the form of the strip of wiring  16  that was located at the cell mounting side to provide an insulation layer. Furthermore, insulating film was stuck to the PET film outside the teeth of an end of wirings  12  and  13  in a direction in which they extend to provide an insulation layer. 
     Then, resin composition  17   a  was applied through a dispenser on the wiring sheet  10  wirings for n and p types  12  and  13  at their respective surfaces, and thereafter,  12  back electrode type solar cells  20  were disposed on wiring sheet  10  so that the electrode for n type  24  of back electrode type solar cell  20  of the  FIG. 2(   a ) and  FIG. 2(   b ) configuration was disposed on the wiring sheet  10  wiring for n type  12  and the back electrode type solar cell  20  electrode for p type  25  was disposed on the wiring sheet  10  wiring for p type  13 . 
     Then, a laminator was employed to pressurize and heat resin composition  17   a  to 150° C. to set it to bond the back electrode type solar cell  20  electrode for n type  24  and the wiring sheet  10  wiring for n type  12  together and also bond the back electrode type solar cell  20  electrode for p type  25  and the wiring sheet  10  wiring for p type  13  together to fabricate a solar cell with a wiring sheet. 
     Thereafter, the solar cell with the wiring sheet fabricated as described above was disposed between ethylene vinyl acetate (EVA) resin placed on a glass substrate and 
     EVA resin placed on PET film. Thereafter, laminator equipment was used and vacuum press was performed to press the glass substrate&#39;s EVA resin to back electrode type solar cell  20  with the wiring sheet and press the PET film&#39;s EVA resin to wiring sheet  10  of the solar cell with the wiring sheet and in that condition heat the EVA resin to 125° C. to set it. The EVA resin set between the glass substrate and the PET film thus sealed the solar cell with the wiring sheet therein to fabricate the solar cell module of example  1 . The above heat treatment simultaneously caused stress in wiring sheet  10 , which was concentrated at the plurality of holes of the wiring for connection  14  in portion  10   b   1  between cell mounting portions, and the wiring sheet was deformed to form bent portion  10   c  projecting toward the back electrode type solar cell, as shown in  FIG. 5(   b ). 
     The solar cell module of example 1 fabricated as above underwent a temperature cycle test at −40° C. to 85° C. While the wiring sheet  10  insulating base material  11  or the PET film thermally contracted, back electrode type solar cells  20  had their spacing substantially unchanged and there was no misalignment of the cells observed, and the solar cell module did not have unsatisfactory insulation, electrical leakage, short circuit, or cracking of a cell, or the like. Furthermore, the solar cell with the wiring sheet in the sealing step was also not observed to have a cell misaligned and did not have unsatisfactory insulation, electrical leakage, short circuit, or cracking of a cell, or the like. 
     Example 2 
     In example 1, a resin composition was used to bond a wiring sheet and a back electrode type solar cell together and subsequently a sealing material was used to seal them to fabricate a solar cell module. In example 2, the wiring sheet and the back electrode type solar cell were not bonded together: they were only sealed with a sealing material to fabricate a solar cell module. 
     Hereinafter, example 2 will be described only at the portion different than example 1. Example 2 is similar to example 1 until  12  back electrode type solar cells  20  are disposed on wiring sheet  10 . 
     Then, the wiring sheet and solar cells thus stacked in layers were disposed between ethylene vinyl acetate (EVA) resin placed on a glass substrate and EVA resin placed on PET film. Thereafter, laminator equipment was used to press the glass substrate&#39;s EVA resin to back electrode type solar cell  20  with the wiring sheet and press the PET film&#39;s EVA resin to wiring sheet  10  of the solar cell with the wiring sheet and in that condition heat the EVA resin to 125° C. to set it. The EVA resin set between the glass substrate and the PET film thus sealed the solar cell with the wiring sheet therein to fabricate the solar cell module of example 2. The above heat treatment simultaneously caused stress in wiring sheet  10 , which was concentrated at the plurality of holes of the wiring for connection  14  in portion  10   b   1  between cell mounting portions, and similarly as has been described in example 1, the wiring sheet was deformed to form bent portion  10   c  projecting toward the back electrode type solar cell, as shown in  FIG. 5(   b ). 
     The solar cell module of example 2 fabricated as above underwent a temperature cycle test at −40° C. to 85° C. While the wiring sheet  10  insulating base material  11  or the PET film thermally contracted, back electrode type solar cells  20  had their spacing substantially unchanged and there was no misalignment of the cells observed, and the solar cell module did not have unsatisfactory insulation, electrical leakage, short circuit, or cracking of a cell, or the like. Furthermore, the solar cell with the wiring sheet in the sealing step was also not observed to have a cell misaligned and did not have unsatisfactory insulation, electrical leakage, short circuit, or cracking of a cell, or the like. 
     Comparative Example 
     Comparative examples of solar cells with wiring sheets and solar cell modules similar to those of examples 1 and 2, respectively, were fabricated except that the PET film used for the wiring sheet was not provided with an insulation layer thereon at a cell mounting side between adjacent cell mounting portions when the wiring sheet was fabricated as a solar cell with a wiring sheet or a solar cell module. 
     The solar cell modules of the comparative examples thus fabricated underwent a sealing step. Their wiring sheets were deformed and it was observed that the wiring sheets had wirings in contact with portions other than electrodes of back electrode type solar cells. Furthermore, after the sealing step, misalignment was visually observed between a cell and a wiring, and this misalignment was of an extent forming short circuit  16   a , as has been described with reference to  FIG. 9 ,  20   b . These resulted in electrical short circuit. 
     It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in any respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims. 
     INDUSTRIAL APPLICABILITY 
     The present invention relates to wiring sheets, solar cells with wiring sheets, solar cell modules, methods for fabricating solar cells with wiring sheets, and methods for fabricating solar cell modules. 
     REFERENCE SIGNS LIST 
       10 : wiring sheet,  10   a:  cell mounting portion,  10   b:  portion between adjacent cell mounting portions,  10   c:  bent portion,  10   d:  a plurality of holes,  101 : insulation layer,  11 : insulating base material,  12 ,  12   a:  wiring for n type,  13 ,  13   a:  wiring for p type,  14 : wiring for connection (or a connection portion),  16 : wiring,  17   a:  resin composition,  17 : curing resin,  18 : substantially orthogonal direction,  20 : back electrode type solar cell,  21 : semiconductor substrate,  22 : n type impurity diffusion region,  23 : p type impurity diffusion region,  24 : electrode for n type,  25 : electrode for p type,  26 : passivasion film,  27 : antireflection film,  30 : transparent substrate,  31 : sealing material,  31   a:  first transparent resin,  31   b:  second transparent resin,  32 : back surface protection sheet.