Patent Publication Number: US-2015059835-A1

Title: Photoelectric Conversion Device

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation under 35 U.S.C. §120 of PCT/JP2013/001215, filed on Feb. 28, 2013, which is incorporated herein by reference and which claimed priority to Japanese Patent Application No. 2012-123304 filed on May 30, 2012. The present application likewise claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2012-123304 filed on May 30, 2012, the entire content of which is also incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present disclosure relates to a photoelectric conversion device. 
     BACKGROUND ART 
     As a power generation system using sunlight, a photoelectric conversion panel in which semiconductor thin films of amorphous, microcrystal or the like are laminated is used. In applying such a photoelectric conversion panel to a solar photovoltaic system, it is installed as a photoelectric conversion device (module) which is equipped with a module frame member in an outer periphery part of the device. 
       FIG. 12  to  FIG. 14  show structure examples generally used in the photoelectric conversion device (module).  FIG. 12  shows a super straight structure used in a solar battery such as a thin film silicon solar battery, and  FIG. 13  shows a super straight structure used in a single-crystalline or polycrystalline silicon solar battery. In this structure, a photoelectric conversion panel  100  is sealed by a glass plate (glass substrate)  10  and a sealing member  12 , and furthermore, a back sheet  14  having a metal thin film for preventing ingression of moisture or the like during outdoor use is superposed on the sealing member  12  side. Further, an end surface seal  16  for preventing ingress of moisture or the like from an end surface and breakage is provided for an outer periphery of the photoelectric conversion panel  100 , and the outside of the seal is reinforced by a module frame member  18 . 
       FIG. 14  shows an example of a glass package structure. In this structure, the above-described back sheet  14  is replaced with a glass plate  20 , and an end surface seal  22  is filled between the glass plate  10  on a front surface side and the glass plate  20  on a rear surface side at an end part of the photoelectric conversion panel  100  to prevent ingression of moisture or the like. 
     On the other hand, a technique of welding glasses plates by irradiating laser beam having a pulse width of femtoseconds was disclosed. 
     In the super straight structure, there is a risk of ingress of moisture or the like into the back sheet  14  and the sealing member  12  permeating them if outdoor use of the structure continues for a long period of time. Further, there is also a risk of the occurrence of output reduction, failure such as disconnection, and changes in external appearance such as peeling of film due to ingress of moisture or the like from an end surface. Moreover, property improvement of a sealing member becomes necessary in order to improved long-term reliability, and a use amount of the member also increases, which could cause an increase in cost. 
     Further, it is difficult for the glass package structure to prevent ingress of moisture or the like from the end surface, and special end surface seal needs to be used, which incurs an increase in cost. Further, in a structure which does not use the module frame member  18 , relative positions of the glass plate  10  and the glass plate  20  could be misaligned due to softening of the sealing member  12  during high temperature in summer. 
     Moreover, on a rear surface side of the photoelectric conversion elements which are formed on a front surface side on the glass plate  10 , power-collecting wiring for collecting power or for extracting power outside the photoelectric conversion device, an insulative coating material for insulating the power-collecting wiring from rear surface electrodes of the photoelectric conversion elements, and the like are disposed, and a gap is generated between the glass plate  10  on a front surface side and the glass plate  20  on a rear surface side. If air is left in the gap, expansion/contraction of air occurs due to irradiation of sunlight or the like, and there is a risk of breakage of the glass plates  10 ,  20 , ingress of water via the gap, or the like. 
     On the other hand, when the glass plate  10  and the glass plate  20  are pressure-bonded to make the gap smaller, stress is applied to the glass plate  20  by protrusions of a structure body on the rear surface of the photoelectric conversion elements, which could cause breakage. 
     SUMMARY OF THE INVENTION 
     One aspect of the present disclosure is a photoelectric conversion device which is provided with: a first glass plate; a photoelectric conversion unit which is fixed on the first glass plate and generates power according to an input of light; and a second glass plate which is disposed so as to cover the photoelectric conversion unit, in which at least a part of the periphery of the second glass plate and that of the first glass plate are melted and bonded to each other, and a plurality of photoelectric conversion elements are connected in series or parallel in the photoelectric conversion unit. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a plan view showing a constitution of a photoelectric conversion device in a first embodiment of the present disclosure. 
         FIG. 2  is a cross-sectional view showing the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 3  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 4  is a plan view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 5  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 6  is a view for explaining a manufacturing method of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 7  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 8  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 9  is a plan view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 10  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 11  is a plan view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 12  is a cross-sectional view showing another example of a constitution of a conventional photoelectric conversion device. 
         FIG. 13  is a cross-sectional view showing another example of the constitution of the conventional photoelectric conversion device. 
         FIG. 14  is a cross-sectional view showing another example of the constitution of the conventional photoelectric conversion device. 
         FIG. 15  is a plan view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 16  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the first embodiment of the present disclosure. 
         FIG. 17  is a cross-sectional view showing a constitution of a photoelectric conversion device in a second embodiment of the present disclosure. 
         FIG. 18  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the second embodiment of the present disclosure. 
         FIG. 19  is a cross-sectional view showing another example of the constitution of the photoelectric conversion device in the second embodiment of the present disclosure. 
         FIG. 20  is a view for explaining a manufacturing method of a photoelectric conversion device in a third embodiment of the present disclosure. 
         FIG. 21  is a view for explaining a manufacturing method of the photoelectric conversion device in the third embodiment of the present disclosure. 
         FIG. 22  is a plan view showing a constitution of a photoelectric conversion device in a fourth embodiment of the present disclosure. 
         FIG. 23  is a cross-sectional view showing the constitution of the photoelectric conversion device in the fourth embodiment of the present disclosure. 
         FIG. 24  is a plan view and a cross-sectional view showing the constitution of the photoelectric conversion device in the fourth embodiment of the present disclosure. 
         FIG. 25  is a cross-sectional view showing a constitution of a photoelectric conversion device in a fifth embodiment of the present disclosure. 
         FIG. 26  is a plan view showing a constitution of photoelectric conversion device in a sixth embodiment of the present disclosure. 
         FIG. 27  is a cross-sectional view showing a constitution of a current extraction part in the sixth embodiment the present disclosure. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     &lt;Basic Constitution&gt; 
     A photoelectric conversion device  200  in the first embodiment of the present disclosure is constituted by including a front surface glass plate (glass substrate)  30 , a photoelectric conversion unit  32 , and a rear surface glass plate  34  as shown in the external appearance plan view of  FIG. 1  and the cross-sectional view of  FIG. 2 . The photoelectric conversion device  200  shows an example applied to a thin film silicon solar battery module. It should be noted that  FIG. 2  is a cross-sectional view taken along line a-a of  FIG. 1 . In  FIG. 2 , thickness of each constituent part is expressed in a ratio different from actual thickness in order to clearly show each constituent part of the photoelectric conversion device  200 . 
     As the front surface glass plate  30 , a glass plate of 1 m square and 4 mm thickness is applied for example. However, the invention is not limited to this, but may be any plate which is suitable for forming the photoelectric conversion unit  32  and capable of mechanically supporting the photoelectric conversion device  200 . Input of light to the photoelectric conversion device  200  is performed basically from the front surface glass plate  30  side. 
     The photoelectric conversion unit  32  is formed on the front surface glass plate  30 . The photoelectric conversion unit  32  is formed by laminating a transparent electrode, a photoelectric conversion unit, a rear surface electrode and the like. As the transparent electrode, a film formed by combining at least one type or plural types out of transparent conductive oxide (TCO) in which tin (Sn), antimony (Sb), fluorine (F), aluminum (Al) or the like is doped with tin oxide (SnO 2 ), zinc oxide (ZnO), indium tin oxide (ITO) or the like, for example, can be used. Further, the photoelectric conversion unit should be an amorphous silicon photoelectric conversion unit (a-Si unit), a microcrystal silicon photoelectric conversion unit (μc-Si unit) or the like, for example. The photoelectric conversion unit may have a structure in which a plurality of the photoelectric conversion units are laminated such as a tandem type and a triple type. The rear surface electrode may be the transparent conductive oxide (TCO) reflective metal, or a laminated structure thereof. Tin oxide (SnO 2 ), zinc oxide (ZnO), indium tin oxide (ITO) or the like is used as the transparent conductive oxide (TCO), and metal such as silver (Ag) and aluminum (Al) is used as the reflective metal. 
     The rear surface glass plate  34  is provided so as to cover the photoelectric conversion unit  32  formed on the front surface glass plate  30 . The rear surface glass plate  34  has substantially the same size as the front surface glass plate  30  for example, and a glass plate having the thickness of 2 mm is applied. However, the plate is not limited to this. 
     The front surface glass plate  30  and the rear surface glass plate  34  are melted and bonded in a bonding region A of their outer peripheral regions. The bonding region A is provided for peripheral part B where the photoelectric conversion unit  32  is not formed in the front surface glass plate  30 . The peripheral part B (region not hatched in  FIG. 1 ) can be provided by removing the photoelectric conversion unit  32 , which was formed once on the front surface glass plate  30 , by laser or the like for example. To melt and bond the front surface glass plate  30  and the rear surface glass plate  34 , it is preferred to make the peripheral part of at least one of the front surface glass plate  30  and the rear surface glass plate  34  have a bent state as shown in  FIG. 2 . 
     It should be noted that the photoelectric conversion device  200  may be provided with interconnectors  36  for extracting power generated in the photoelectric conversion unit  32  to the outside. Herein, the film thickness of the photoelectric conversion unit  32  is several μm and the thickness of the interconnectors  36  is approximately several hundred μm, so that when the width of the peripheral part B is approximately 10 mm, the four outer peripheral sides are completely adhered by elastic deformation of either the front surface glass plate  30  or the rear surface glass plate  34 , and the plates can be melted and bonded in the bonding region A. 
     The cross-sectional view in  FIG. 3  shows a configuration example of extracting generated electric power via the interconnectors  36 . In the configuration example, openings C are provided for predetermined positions of the rear surface glass plate  34 , and wiring cords  38  being current paths are allowed to pass through the openings. Moreover, terminal boxes  40  are disposed at positions overlapping the openings C, and the wiring cords  38  are connected to the terminal boxes  40 . In this way, the openings C are covered by the terminal boxes  40 , and generated electric power can be extracted to the outside without impairing a sealing effect. It should be noted that the inside of the terminal boxes  40  may be filled with butyl resin or the like to make sealing more secure. Further, the openings C may be provided for the front surface glass plate  30  side. 
     Further, the plan view in  FIG. 4  and the cross-sectional view in  FIG. 5  show another configuration example for extracting generated electric power.  FIG. 5  shows a cross section taken along line b-b of  FIG. 4 . In this example, the bonding region A is not provided for a part of the outer periphery of the front surface glass plate  30  and the rear surface glass plate  34  but openings D are formed. The wiring cords  38  being a current path are allowed to go through the openings D, and only these portions are sealed by end surface seal members  42 . Portions sealed by the end surface seal members  42  are likely to be an ingress route for moisture or the like from the external environment, but reliability of the photoelectric conversion device  200  can be improved by making the regions shorter than a conventional structure. 
     &lt;Melting and Bonding Method&gt; 
       FIG. 6  shows a method for melting and bonding the front surface glass plate  30  and the rear surface glass plate  34  in the photoelectric conversion device  200  in the bonding region A. 
     As shown in  FIG. 2 , a peripheral part of at least one of the front surface glass plate  30  and the rear surface glass plate  34  is bent to make the peripheral part B of the front surface glass plate  30  and the rear surface glass plate  34  be an adhered state. Then, a laser beam  52  is irradiated from a laser device  50  focusing on a contact surface of the adhered peripheral part B, and is scanned along the outer peripheral four sides of the front surface glass plate  30  and the rear surface glass plate  34 . 
     It is preferred that the laser beam  52  be femtosecond laser beam. Specifically, it is preferred that the laser beam  52  have a pulse width of 1 nanosecond or less. Further, it is preferred that the laser beam  52  have a wavelength at which adsorption occurs on at least one of the front surface glass plate  30  and the rear surface glass plate  34 . For example, it is preferred that the laser beam  52  have a wavelength of 800 nm. Moreover, it is preferred that the laser beam  52  irradiate at sufficient energy density and scanning speed as to melt the front surface glass plate  30  and the rear surface glass plate  34 . For example, it is preferred that the laser beam  52  irradiate at pulse energy of 10 micro-joule (μJ) per one pulse. Further, it is preferred to scan the laser beam  52  at a scanning speed of 60 mm/minute. Further, the laser beam  52  may irradiate either from the front surface glass plate  30  side or the rear surface glass plate  34  side. 
     Now, in the case where the thickness of the photoelectric conversion unit  32  and the interconnectors  36  is large and a gap between the peripheral part of the front surface glass plate  30  and the rear surface glass plate  34  becomes larger, filler  54  may be filled in the gap, and the filler  54  is melted to melt and bond the front surface glass plate  30  and the rear surface glass plate  34  as shown in the cross-sectional view in  FIG. 7 . 
     As the filler  54 , it is preferred to apply a material including an element which is capable of melting and bonding the front surface glass plate  30  and the rear surface glass plate  34  such as Si, SiO, SiO 2  and SiO x . 
     Further, the laser beam  52  can irradiate either from the front surface glass plate  30  side or the rear surface glass plate  34  side, so that in the case where the photoelectric conversion unit  32  (including silicon substrate) itself is thick like a crystalline silicon solar battery, a constitution in which the front surface of the filler  54  is melted and bonded with the front surface glass plate  30  and the rear surface of the filler  54  is melted and bonded with the rear surface glass plate  34  is acceptable as shown in  FIG. 8 . 
     In such a case, a conventional sealing member  56  may be used in combination in order to planarize unevenness caused by the photoelectric conversion unit  32 . Further, in order to further increase a sealing effect, a conventional end surface seal  58  and a conventional frame  60  may be used in combination. 
     Further, the bonding region A does not need to be a single line, and a plurality of the bonding regions A may be provided, as shown in the plan view in  FIG. 9  and the cross-sectional view in  FIG. 10 . As shown in  FIG. 9  and  FIG. 10 , by providing a plurality of the bonding regions A in parallel, bonding strength and airtightness of the front surface glass plate  30  and the rear surface glass plate  34  can be further improved. Moreover, as shown in  FIG. 11 , the bonding region A may be provided in a lattice shape. Thus, bonding strength and airtightness can be further improved. It should be noted that  FIG. 11  shows the bonding region A in lines. 
     The plan view in  FIG. 15  and the cross-sectional view in  FIG. 16  show another configuration example for extracting generated electric power.  FIG. 16  shows the cross section taken along line d-d in  FIG. 15 . In the configuration example, first power-collecting wirings  62  and second power-collecting wirings  64  are formed for extracting power generated in the photoelectric conversion unit  32 . The first power-collecting wirings  62  are wirings for collecting power from the plurality of photoelectric conversion units  32 , and the second power-collecting wirings  64  are wirings which connect the first power-collect ing wirings  62  to a terminal box  66 . It should be noted that the photoelectric conversion units  32  may be connected not in parallel directions but in serial directions. In this case, solar battery cells divided in serial directions are connected in series by the transparent electrode and the rear surface electrode. 
     The first power-collecting wirings  62  are provided on the rear surface electrode of the photoelectric conversion units  32  in an extending manner. The first power-collecting wirings  62  are formed to connect positive electrodes and negative electrodes of a photoelectric conversion layer which is divided in a parallel manner near end sides of the photoelectric conversion device  200 . Therefore, the first power-collecting wirings  62  are provided in an extending manner along a direction orthogonal to a parallel divided direction of the photoelectric conversion layer. In the configuration example, the first power collecting wirings  62  are provided in an extending manner in vertical directions along end sides on right and left as shown in  FIG. 15 . Thus, positive electrodes and negative electrodes of the photoelectric conversion unit  32  which are connected in series are connected in parallel. 
     Next, an insulating coating material  68  is arranged in order to form electrical insulation between the second power-collecting wirings  64  and the rear surface electrode. The insulating coating material  68  is provided in an extending manner on the rear surface electrode of the photoelectric conversion unit  32  from the vicinity of the first power-collecting wirings  62 , which are provided along the end sides on right and left of the photoelectric conversion device  200 , to a disposed position of the terminal box  66  at the central part, as shown in  FIG. 15  and  FIG. 16 . Herein, as shown in  FIG. 15 , the insulating coating material  68  is provided in an extending manner along lateral directions from the vicinity of the first power-collecting wirings  62  on the right and left toward the terminal box  66 . It is preferred that the insulating coating material  68  be polyester (PE), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polyimide, polyvinyl fluoride or the like for example. Further, as the insulating coating material  68 , it is preferred to use a material on the rear surface of which adhesive agent is coated in a sealed state. 
     The second power-collecting wirings  64  are provided in an extending manner from areas on the first power-collecting wirings on the right and left toward the central part of the photoelectric conversion device  200  along an area on the insulating coating material  68 , as shown in  FIG. 15  and  FIG. 16 . The insulating coating material  68  is sandwiched between the second power-collecting wirings  64  and the rear surface electrode of the photoelectric conversion units  32 , and electrical insulation between the second power-collecting wirings  64  and the rear surface electrode is maintained. On the other hand, one end of each of the second power-collecting wirings  64  is provided in an extending manner onto the first power-collecting wiring  62 , and electrically connected to the first power-collecting wiring  62 . For example, it is preferred to electrically connect the second power-collecting wirings  64  to the first power-collecting wirings  62  by ultrasonic soldering or the like. The other end of each of the second power-collecting wirings  64  is connected to electrode terminals in the terminal box  66  (described later). 
     The rear surface of the photoelectric conversion device  200  is sealed by the rear surface glass plate  34 . At this point, end part of the second power-collecting wirings  64  are pulled out through holes X provided near the attaching position of the terminal box  66  on the rear surface glass plate  34 . Then, the end part of each of the second power-collecting wirings  64  is electrically connected to terminal electrodes in the terminal box  66  by soldering or the like, insulating resin  70  such as silicon is filled into a space in the terminal box  66 , and the box is closed with a lid. It is preferred to attach the terminal box  66  in the vicinity of the holes X, which are used for pulling out the end part of each of the second power-collecting wirings  64 , by adhering using silicon or the like. 
     The front surface glass plate  30  and the rear surface glass plate  34  are melted and bonded in the bonding region A of their outer peripheral regions. The bonding region A is provided for the peripheral part B where the photoelectric conversion unit  32  is not formed in the front surface glass plate  30 . The peripheral part B (a region not hatched in  FIG. 1 ) can be provided by removing the photoelectric conversion unit  32  which was formed once on the front surface glass plate  30  by laser or the like, for example. To melt and bond the front surface glass plate  30  and the rear surface glass plate  34 , it is preferred to make a peripheral part of at least one of the front surface glass plate  30  and the rear surface glass plate  34  be a bent state as shown in  FIG. 16 . 
     Second Embodiment 
     A photoelectric conversion device  300  in the second embodiment is constituted by including a sealing member  80  in addition to the front surface glass plate  30 , the photoelectric conversion unit  32 , and the rear surface glass plate  34  as shown in the cross-sectional view in  FIG. 17 .  FIG. 17  expresses the thickness of each constituent part in a ratio different from the actual thickness to clearly show each constituent part of the photoelectric conversion device  300 . 
     In the photoelectric conversion device  300 , before covering the photoelectric conversion unit  32  by the rear surface glass plate  34 , the sealing member  80  is coated on the rear surface of the photoelectric conversion unit  32 , and covered by the rear surface glass plate  34  after baking. 
     Herein, it is preferred that the sealing member  80  be a material having a rate of thermal expansion closer to that of the front surface glass plate  30  and the rear surface glass plate  34 , and it is preferred to use a silicon oxide based material. It is preferable that the silicon oxide-based material be a material containing SiC, SiO 2  or SiO, by at least 50% or more as a main component. By using a silicon oxide-based material as the sealing member  80 , coefficients of thermal expansion the front surface glass plate  30  and the rear surface glass plate  34  can be made closer, and occurrence of thermal stress between the front surface glass plate  30 , the rear surface glass plate  34  and the sealing member  80 , which arises from heating by sunlight irradiation or the like, can be suppressed. Therefore, breakage of the front surface glass plate  30 , the rear surface glass plate  34  and the sealing member  80  caused by thermal stress can be prevented. 
     For example, silica sol (silica gel) which is formed by mixing microparticles of silicon oxide (glass) into a binder of resin such as acrylic resin or solvent such as water and organic solvent is coated by a spray coating method, a spin coater coating method or the like. Then, the sealing member  80  is solidified by heating at several tens of ° C. to several hundred ° C., covered by the rear surface glass plate  34 , and the front surface glass plate  30  and the rear surface glass plate  34  are bonded. 
     As described, at least a part of a gap which occurs close to power collecting wirings, an insulating coating material or the like between the front surface glass plate  30  and the rear surface glass plate  34  is buried by the silicon oxide-based sealing member  80 . In this way, air in the gap which occurs between the front surface glass plate  30  and the rear surface glass plate  34  is eliminated, any effect due to expansion/contraction of air can be reduced, and breakage of the front surface glass plate  30  or the rear surface glass plate  34  can be suppressed. Further, ingress of water via the gap between the front surface glass plate  30  and the rear surface glass plate  34  can be prevented. 
       FIG. 17  is one example of the photoelectric conversion device  300  in the second embodiment. This example has a structure in which the sealing member  80  is coated on the entire surface of a side of the front surface glass plate  30  on which the photoelectric conversion unit  32  is formed. In this case, after covering with the rear surface glass plate  34 , the front surface of the sealing member  80  in the outer periphery portion of the photoelectric conversion device  300  and the front surface glass plate  30  may be melted and bonded, and the rear surface of the sealing member  80  and the rear surface glass plate  34  may be melted and bonded. 
     With such a structure, the front surface glass plate  30  and the rear surface glass plate  34  can be melted and bonded without widely bending both plates. Therefore, bending stress applied to the front surface glass plate  30  and the rear surface glass plate  34  can be made smaller, and breakage of the front surface glass plate  30  or the rear surface glass plate  34  can be suppressed. 
       FIG. 18  is another example of the photoelectric conversion device  300  in the second embodiment. This example has a structure in which the sealing member  80  is coated leaving an outer periphery portion of the front surface glass plate  30  on a side on which the photoelectric conversion unit  32  is formed. In this case, after covering with the rear surface glass plate, the front surface glass plate  30  and the rear surface glass plate  34  are melted and bonded in a state where a peripheral part of at least one of the front surface glass plate  30  and the rear surface glass plate  34  is bent. It is preferred that the bonding region be a peripheral part in the front surface glass plate  30  where the photoelectric conversion unit  32  is not formed. 
     In this case, since the front surface glass plate  30  and the rear surface glass plate  34  are directly melted and bonded, bonding force can be increased. Further, glass plates are pressed against each other by bending of the front surface glass plate  30  or the rear surface glass plate  34 , and adhesion property of the front surface glass plate  30  and the rear surface glass plate  34  can be improved. In this way, air between the front surface glass plate  30  and the rear surface glass plate  34  can be eliminated even more efficiently, which enhances an effect of suppressing breakage of the front surface glass plate  30  or the rear surface glass plate  34  caused by expansion/contraction of air. Further, ingress of water via the gap between the front surface glass plate  30  and the rear surface glass plate  34  can be also reduced more. 
     It should be noted that the structures of  FIG. 17  and  FIG. 18  can be applied to a structure in which the wiring cords  38  are extracted from the openings D of the peripheral part such as a photoelectric conversion device  100  shown in  FIG. 5 . In this case, a constitution in which the openings D are simultaneously sealed by the sealing member  80  by coating the sealing member  80  on the regions of the openings D is acceptable. 
       FIG. 19  is another example of the photoelectric conversion device  300  in the second embodiment. This example has a structure in which the sealing member  80  is coated leaving the outer periphery portion of the front surface glass plate  30  on the side on which the photoelectric conversion unit  32  is formed, the filler  54  is filled between the front surface glass plate  30  and the rear surface glass plate  34 , and the filler  54  is melted to melt and bond the front surface glass plate  30  and the rear surface glass plate  34 . 
     Even with this structure, similarly to the example in  FIG. 17 , bending stress applied to the front surface glass plate  30  and the rear surface glass plate  34  can be made smaller, and breakage of the front surface glass plate  30  or the rear surface glass plate  34  can be suppressed. The constitution in which the filler  54  and the sealing member  80  are used in combination can also be applied to a module of the thick photoelectric conversion unit  32  such as the crystalline silicon solar battery shown in  FIG. 8 . 
     Further, in the examples in  FIG. 18  and  FIG. 19 , it is also preferred to perform treatment of covering by the rear surface glass plate  34  before completely solidifying the sealing member  80 . By performing sealing in a state where fluidity of the sealing member  80  is high, filling factor of the sealing member  80  in a gap between the front surface glass plate  30  and the rear surface glass plate  34  in the peripheral part or a gap formed by the filler  54  and the sealing member  80  can be further improved. 
     Now, a similar effect can be obtained by treatment in which the sealing member  80  is completely solidified in a region other than the peripheral part of the photoelectric conversion device  300 , then the sealing member  80  is newly coated on the peripheral part only, and covered by the rear surface glass plate  34  in a state where the material is not completely solidified. 
     Third Embodiment 
     A photoelectric conversion device  400  in a third embodiment has a constitution similar to the photoelectric conversion device  100  in the first embodiment, in which air in the gap between the front surface glass plate  30  and the rear surface glass plate  34  is discharged into a decompressed state to the atmospheric. 
       FIG. 20  shows a laminating device  500  for the photoelectric conversion device  400 . The laminating device  500  is constituted by including a chamber  90 , a heater  92  and a diaphragm  94 . The laminating device  500  has a structure in which an upper region Y and a lower region X of the chamber  90  are partitioned by the elastic diaphragm  94 . Further, the lower region X of the chamber  90  is provided with the heater  92  which is mounted on and heats the photoelectric conversion device  400 . 
     In laminating the photoelectric conversion device  400 , after the front surface glass plate  30  and the rear surface glass plate  34  are melted and bonded in the bonding region A as shown in  FIG. 20 , the device is installed on the heater  92  in a state where sealing members  82  are disposed in the openings C of the wiring cords  38  of the interconnectors  36 . It is preferred that the sealing members  82  be butyl resin for example. At this point, air or the like is supplied to the lower region X of the chamber  90 , and the photoelectric conversion device  400  is installed on the heater  92  in a state where the diaphragm  94  is pulled upward by evacuating the upper region Y. Then, while the photoelectric conversion device  400  is being heated by the heater  92 , the lower region X of the laminating device  500  is evacuated as shown in  FIG. 21 , and the sealing members  82  are pressed against the openings C by the diaphragm  94  by supplying air to the upper region Y. In this way, the sealing members  82  softened by heating are pressed against the openings C, the sealing members  82  are deformed into the shape of the openings C, and the openings C are sealed. 
     At this point, air collected in the gap between the front surface glass plate  30  and the rear surface glass plate  34  is simultaneously exhausted from the openings C, and the openings are sealed in a state where pressure in the gap between the front surface glass plate  30  and the rear surface glass plate  34  is decompressed more than atmospheric pressure. 
     As described, air in the gap, which occurs because of the power-collecting wiring, the insulating coating material or the like between the front surface glass plate  30 , and the rear surface glass plate  34 , can be exhausted. In this way, affect of expansion/contraction of air in the gap between the front surface glass plate  30  and the rear surface glass plate  34  can be reduced, and breakage of the front surface glass plate  30  or the rear surface glass plate  34  can be suppressed. Further, ingress of water via the gap between the front surface glass plate  30  and the rear surface glass plate  34  can be prevented. 
     It should be noted that the constitution in which sealing is performed in the state where air between the front surface glass plate  30  and the rear surface glass plate  34  is exhausted can be similarly applied in the constitution shown in  FIG. 4  in which the wiring cords  38  are pulled out from the peripheral part of the photoelectric conversion device or the constitution shown in  FIG. 15  in which the wiring cords  38  are pulled out from the central part of the photoelectric conversion device as well. 
     Further, in the third embodiment, air between the front surface glass plate  30  and the rear surface glass plate  34  is exhausted from the openings C for pulling out the wiring cords  38  to the outside, and the openings C are sealed in the exhausted state, but the invention is not limited to this. A constitution in which openings other than the openings for pulling out the wiring cords  38  are provided for the photoelectric conversion device, air between the front surface glass plate  30  and the rear surface glass plate  34  is exhausted from the openings, and the openings are sealed by the sealing members  82 , is also acceptable. 
     Fourth Embodiment 
     A photoelectric conversion device  600  in the fourth embodiment of the present disclosure is constituted by including the front surface glass plate  30 , photoelectric conversion units  602 , and the rear surface glass plate  34  as shown in the external appearance plan view in  FIG. 22  and the cross-sectional view in  FIG. 23 . In this embodiment as well, at least a part of the front surface glass plate  30  and that of the rear surface glass plate  34  are melted and bonded to each other in the bonding region A. It should be noted that  FIG. 23  is a cross-sectional view taken along line e-e  FIG. 22 . 
     The photoelectric conversion element is a rear surface bonding photoelectric conversion element in which both of a positive side electrode  104  and a negative side electrode  106  are provided on a rear surface side being the opposite side of the light receiving surface, as shown in the plan view seen from the rear surface side being the opposite side of the light receiving surface in  FIG. 24 . It should be noted that the comb-shaped positive side electrode  104  is not hatched and the negative side electrode  106  is hatched in  FIG. 24 , where the electrodes are combined with each other, to facilitate understanding. As shown in the front and side views in  FIG. 24 , in this embodiment, three photoelectric conversion elements are installed so as to face in opposite directions to each other on the front surface glass plate  30 , and electrically connected in series by serial interconnectors  108 . Moreover, the elements are connected in parallel by parallel interconnectors  110  at both ends of the photoelectric conversion device (top and bottom ends in  FIG. 22 ). A plurality of photoelectric conversion elements are connected in series or parallel and the photoelectric conversion unit  602  is constituted in this manner. 
     The serial interconnectors  108  are electrically connected severally to the positive side electrode  104  and the negative side electrode  106  at both ends of a photoelectric conversion unit  102  (right and left ends in  FIG. 24 ), and connect the positive side electrode  104  and the negative side electrode  106  of adjacent photoelectric conversion units  102  in series. The parallel interconnectors  110  electrically connect the serial interconnectors  108  connected to the positive side electrode  104  or the serial interconnectors  108  connected to the negative side electrode  106  in parallel severally outside the photoelectric conversion units  102  (top and bottom ends in  FIG. 24 ). Ribbon-shaped copper foil is coated by solder on the serial interconnectors  108 , and as shown in the side view in  FIG. 24 , a constitution in which an insulating coating material  112  is applied to regions corresponding to the vicinity of the outer periphery of the photoelectric conversion element is acceptable. The serial interconnectors  108  are thermocompression-bonded to the positive side electrode  104  and the negative side electrode  106 . 
     By having the constitution in which the photoelectric conversion elements are connected in series or parallel in this manner, voltage and current which are optimum for inputting a load or a power conditioner connected to the photoelectric conversion device  600  can be extracted. It should be noted that the photoelectric conversion element is not limited to the rear surface bonding photoelectric conversion element, but thin-film photoelectric conversion elements having at least a pair or PIN junctions may be connected in series or parallel for example. 
     Fifth Embodiment 
     A photoelectric conversion device  700  in a fifth embodiment of the present disclosure is constituted by including low-refractive-index layer  112  on the front surface glass plate in addition to the front surface glass plate  30 , the photoelectric conversion unit  602 , and the rear surface glass plate  34  as shown in  FIG. 25 . In this embodiment as well, at least a part of the front surface glass plate  30  and that of the rear surface glass plate  34  are melted and bonded to each other in the bonding region A. 
     The front surface glass plate  30  is a tempered glass plate with a thickness of 1.8 mm, and which is fabricated by an air-cooling and tempering method. The front surface glass plate  30  has higher tolerance to damage caused by wind and rain in outdoor use compared to the non-tempered front surface glass plate  34 . 
     As shown in  FIG. 25 , the thickness of the rear surface glass plate  34  is made thicker than the thickness of the front surface glass plate  30  in this embodiment. For example, the thickness of the rear surface glass plate  34  should be approximately 5.0 mm. In many cases, the device is installed by adhering metal attaching bases  114  to the rear surface glass plate  34  with adhesive agent or the like. In the case where external force caused by wind and rain is applied to the photoelectric conversion device  700 , larger deformation occurs in the front surface glass plate  30  compared to the rear surface glass plate  34  adhered to the attaching bases  114 . Therefore, the front surface glass plate  30  is prone to be broken easily. At this point, the thinner the thickness of the front surface glass plate  30  is, the smaller a deformation amount of the outermost surface can be made, so that breakage can be suppressed. It should be noted that the rear surface glass plate  34  may also be a tempered glass plate. 
     Further, the low-refractive-index layer  112  may be formed on the front surface glass plate  30  as shown in  FIG. 25 . The low-refractive-index layer  112  should be porous silicon oxide or the like, for example. Porous silicon oxide can be formed by coating sol-gel of a silica material such as TEOS (tetramethyl orthosilicate) on the front surface glass plate  30  and baking it. Since an average index of refraction of porous silicon oxide is 1.45, light reflection loss on a front surface of the front surface glass plate  30  with an index of refraction at 1.52 can be reduced. 
     Sixth Embodiment 
     A photoelectric conversion device  800  in a sixth embodiment of the present disclosure is provided with terminal boxes  116  for extracting generated electric current on the rear surface glass plate  34  as shown in  FIG. 26  in addition to the photoelectric conversion device  600  in the fourth embodiment. It should be noted that  FIG. 26  is a plan view of a rear surface side being the opposite side of the light receiving surface of the photoelectric conversion device  800 .  FIG. 27  is a cross-sectional view taken along line f-f of  FIG. 26 . Further, in this embodiment as well, at least a part of the front surface glass plate  30  and the rear surface glass plate  34  is melted and bonded in the bonding region A. 
     A current extraction part of the photoelectric conversion device  800  consists of the serial interconnector  108 , solder  118 , a metal wire  120 , and a low-melting-point glass  122 . Firstly, the metal wire  120  is allowed to go through a through hole  34   a  provided for the rear surface glass plate  34 , and a gap between the through hole  34   a  and the metal wire  120  is filled by the low-melting-point glass  122 . In this way, extraction wiring for generated electric power through the rear surface glass plate  34  is formed by the metal wire  120 , and the rear surface glass plate  34  is airtightly sealed by the low-melting-point glass  122 . The metal wire  120  should be an alloy of iron and nickel in a ration of 50:50 for example. Such an alloy has a coefficient of thermal expansion relatively close to the coefficient of thermal expansion of the low-melting-point glass  122 , and cracking caused by thermal expansion in airtight sealing can be suppressed. Then, tip of the metal wire  120  is connected to the serial interconnector  108  of the photoelectric conversion unit  602 , which is disposed on the front surface glass plate  30 , via the solder  118 . The solder  118  is disposed for the tip of the serial interconnector  108  or the metal wire  120  in advance, and the serial interconnector  108  and the metal wire  120  can be connected by melting through heating the solder via the metal wire  120  exposed outside. Then, in this embodiment as well, at least a part of the front surface glass plate  30  and that of the rear surface glass plate  34  are melted and bonded to each other in the bonding region A. 
     The terminal box  116  includes a cable  124 , solder  126  and insulating resin  128 . The cable  124  is connected to the metal wire  120  by the solder  126 . The terminal box  116  is adhered to the rear surface glass plate  34  by the insulating resin  128 . The insulating resin  128  has a relatively high water vapor barrier property, but is likely to be affected by water vapor in the long run. However, if the structure of the current extraction part such as the photoelectric conversion device  800  is adopted, moisture ingress does not reach the photoelectric conversion element, and a highly airtight photoelectric conversion device can be obtained.