Abstract:
This invention discloses a defect isolation method for thin-film solar cell having at least a defect therein. The thin-film solar cell comprises a substrate, a front electrode layer, an absorber layer and a back electrode layer stacked in such a sequence. The defect isolation method includes the steps of: detecting at least a defect formed in thin-film solar cell and acquiring the positions of the defects, and applying a laser light to scribe the outer circumference of the defects according to the positions of the defects so as to form at least an isolation groove having a closed-curve configuration.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Technical Field 
         [0002]    The present invention relates to a method for defect isolation of a thin-film solar cell and, more particularly, to a method for applying a laser light to form an isolation groove around a defect of a thin-film solar cell and thereby restraining a short circuit from the defect in the thin-film solar cell. 
         [0003]    2. Description of Related Art 
         [0004]    Generally, a thin-film solar cell is formed at least of a transparent substrate, a front electrode layer, an absorber layer, and a back electrode layer sequentially stacked up. During the manufacturing process of a thin-film solar cell, the foregoing layers are deposited and laser light cut so as to form a thin-film solar cell with a plurality of unit cells connected in series. While the layers are being laser light cut, any incomplete cut becomes a defect that may short-circuit the finished thin-film solar cell and thus lower the overall power generation efficiency thereof To solve this problem, Japanese Patent Laid-Open Publication No. H8-037317 provides a method for detecting and removing a short-circuiting defect of a thin-film solar cell, wherein the method comprises determining the location of a defect in a back electrode layer by means of infrared thermal image measurement and then removing the defect with pulse laser light according to the location of the defect. 
         [0005]    Nevertheless, the prior art cited above leaves much room for improvement in terms of defect removal from thin-film solar cell. More specifically, the prior art is directed essentially to the removal of a short-circuiting defect located in the back electrode layer of a thin-film solar cell. In practice, however, the defect of a thin-film solar cell may occur in places other than the back electrode layer, and the defect may cause problems other than a short circuit. As the absorber layer and the front electrode layer are also susceptible to defects of various forms during the manufacturing process of a thin-film solar cell, the above-cited prior art has its limitations in improving defect removal from thin-film solar cell. Therefore, it is a pressing issue for the related industry to provide more effective defect removal from thin-film solar cell than that furnished by the prior art. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    To overcome the aforesaid shortcomings of the prior art, the present invention provides a method for defect isolation of a thin-film solar cell, where the thin-film solar cell has at least a defect that is isolated by means of laser light cutting, mechanical cutting, or chemical etching. The thin-film solar cell comprises a substrate, a front electrode layer, an absorber layer, and a back electrode layer sequentially stacked up. The method includes the steps of: detecting at least a defect of the thin-film solar cell so as to obtain a corresponding location to the defect; and forming at least an isolation groove of a closed-curve configuration around the defect using laser light of a specific wavelength according to the location of the defect. Thus, the isolation groove is formed to restrain the defect from a short circuit in the thin-film solar cell and thereby increases overall power generation efficiency of the thin-film solar cell. 
         [0007]    Therefore, it is a primary objective of the present invention to provide a defect isolation method that detects the position of the defect in the back electrode layer of the thin-film solar cell, and subsequently applies one of ultraviolet, green and infrared laser lights to scribe an isolation groove around the position of the defect based on the position of the defect so as to repair the defect due to restraining its short-circuit effect and further to increase the overall power generation efficiency. 
         [0008]    It is a second objective of the present invention to provide a defect isolation method that detects the position of the defect in the absorber layer of the thin-film solar cell, and subsequently applies one of green and infrared laser lights to scribe an isolation groove around the position of the defect based on the position of the defect so as to repair the defect due to restraining its short-circuit effect and further to increase the overall power generation efficiency. 
         [0009]    It is a third objective of the present invention to provide a defect isolation method that detects the position of the defect in the front electrode layer of the thin-film solar cell, and subsequently applies infrared laser light to scribe an isolation groove around the position of the defect based on the position of the defect so as to repair the defect due to restraining its short-circuit effect and further to increase the overall power generation efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0010]    The structures and technical means adopted by the present invention to achieve the above and other objectives can be best understood by referring to the following detailed description of the preferred embodiments in conjunction with the accompanying drawings, in which: 
           [0011]      FIG. 1A  is a schematic side view of a defect isolation equipment for depicting its use in a first preferred embodiment of the present invention; 
           [0012]      FIG. 1B  is a schematic top view of a thin-film solar cell for depicting a defect before and after isolation according to the first preferred embodiment of the present invention: 
           [0013]      FIG. 2  is a schematic sectional view of a thin-film solar cell for depicting an isolated defect according to a second preferred embodiment of the present invention; 
           [0014]      FIG. 3A  is a schematic sectional view of a thin-film solar cell for depicting an isolated defect according to a third preferred embodiment of the present invention; 
           [0015]      FIG. 3B  is a schematic sectional view of another thin-film solar cell for depicting an isolated defect according to the third preferred embodiment of the present invention; 
           [0016]      FIG. 4A  is a schematic sectional view of a thin-film solar cell for depicting an isolated defect according to a fourth preferred embodiment of the present invention; and 
           [0017]      FIG. 4B  is a schematic sectional view of another thin-film solar cell for depicting an isolated defect according to the fourth preferred embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0018]    The present invention provides a thin-film solar cell, wherein the principle of photoelectric conversion from solar energy is well known to a person of ordinary skill in the art and therefore will not be detailed herein. Besides, it is to be understood that the drawings referred to in the following description are intended to demonstrate features of the present invention only schematically, so the drawings are not necessarily drawn to scale. 
         [0019]    Referred to  FIG. 1A  and  FIG. 1B , it is a method for defect isolation of a thin-film solar cell  10  according to a first preferred embodiment of the present invention, where  FIG. 1A  is a front view of a defect isolation equipment for depicting how to scribe a closed-curve isolation groove around the defect by means of using laser light, and  FIG. 1B  is a top view of a thin-film solar cell having a defect. The thin-film solar cell  10  comprises a substrate  11 , a front electrode layer  12 , an absorber layer  13  and a back electrode layer  14  sequentially stacked up, shown in  FIG. 2 . To begin with, the thin-film solar cell  10  having a defect  15  is placed on a loading stage  22  of a detection device  20 . Then, the detection device  20  is connected with positive and negative electrodes of the thin-film solar cell  10  under test, respectively. The detection device  20  emits electroluminescent (EL) or infrared (IR) light onto the thin-film solar cell  10  so as to determine the actual location of the defect  15  in the thin-film solar cell  10 . Afterward, the detection device  20  transmits the actual location of the defect  15  to a laser light device  24 . The laser light device  24  then scribes the thin-film solar cell  10  with a laser light beam having a specific wavelength, thereby forming at least one isolation groove  16  having a closed-curve configuration around the defect  15 . By so doing, the defect  15  of the thin-film solar cell  10  is effectively isolated or repaired to increase overall power generation efficiency of the thin-film solar cell  10 . While laser light cutting is used for defect isolation in the present embodiment, mechanical cutting or chemical etching may also be used in the present invention for defect isolation as well. 
         [0020]    Referred to  FIG. 2 , it is a method for defect isolation of a thin-film solar cell having a defect within the back electrode layer according to a second preferred embodiment of the present invention. More specifically,  FIG. 2  is a sectional view of a thin-film solar cell  10 . A laser light device  24  is provided to emit one of ultraviolet laser light, green laser light, and infrared laser light so as to partially remove a back electrode layer  14  along a closed curve centered around the defect  15 . Thus, an isolation groove  16  having a closed-curve configuration is formed in the back electrode layer  14  to isolate the defect  15  of the thin-film solar cell  10 . It is applicable that the light device  24  is provided to emit one of green laser light and infrared laser light to partially remove the back electrode layer  14  and absorber layer  13  along a closed curve centered around the defect  15  so as to from an isolation groove (not shown) having a depth extending from the back electrode layer  14  to the absorber layer  13 . It is also applicable that the light device  24  is provided to emit infrared laser light to partially remove the back electrode layer  14 , the absorber layer  13  and the front electrode layer  12  along a closed curve centered around the defect  15  so as to from an isolation groove (not shown) having a depth extending from the back electrode layer  14  through the absorber layer  13  to the front electrode layer  12 . 
         [0021]    When the isolation groove (not shown) has a depth extending from the back electrode layer  14  through the absorber layer  13  to the front electrode layer  12 , and has a first groove width (not shown) in all three layers, it is applicable in case 1 to use one of ultraviolet laser light, green laser light, and infrared laser light of the laser light device  24  to subsequently partially remove the back electrode layer  14  along an edge of the isolation groove in the back electrode layer  14  such that the isolation groove has a newly second groove width (not shown) in the back electrode layer  14  greater than the first groove width in the absorber layer  13 . Alternatively, it is also applicable in case 2 to use one of green laser light and infrared laser light to partially remove both the back electrode layer  14  and the absorber layer  13  along an edge of the isolation groove in the back electrode layer  14  such that the isolation groove has two newly identical second groove widths respectively in the back electrode layer  14  and the absorber layer  13  greater than the first groove width in the front electrode layer  12 . 
         [0022]    According to the case , it is also applicable to further use one of green laser light and infrared laser light to subsequently partially remove the absorber layer  13  adjacent to the edge of the isolation groove in the absorber layer  13  such that the isolation groove has a newly third groove width (not shown) in the absorber layer  13  greater than the first groove width in said front electrode layer. 
         [0023]    In any case described above of the second preferred embodiment, the defect  15  of the thin-film solar cell  10  is isolated so as to repair the defect  15  due to restraining its short-circuit effect and further to increase the overall power generation efficiency of the thin-film solar cell  10 . 
         [0024]    A method according to a third preferred embodiment of the present invention for defect isolation of a thin-film solar cell having a defect within the absorber layer is shown in  FIG. 3A  and  FIG. 3B , where  FIG. 3A  is a sectional view of a thin-film solar cell  10  having a defect  15  isolated by an isolation groove having a first structure, and  FIG. 3B  is a sectional view of a thin-film solar cell  10  having a defect  15  isolated by an isolation groove having a second structure. In the third preferred embodiment, a laser light device  24  is provided to emit infrared laser light so as to implement defect isolation along a closed curve centered around the defect  15  such that a back electrode layer  14 , an absorber layer  13 , and a front electrode layer  12  are all simultaneously partially removed to form an isolation groove  16  of having a closed-curve configuration and a depth extending from the back electrode layer  14  through the absorber layer  13  to the front electrode layer  12 . It is also applicable that the isolation groove can be formed (not shown) by means of using one of ultraviolet laser light, green laser light and infrared laser light to partially removing the back electrode layer  14 , or using one of green laser light and infrared laser light to partially removing the back electrode layer  14  and the absorber layer  13 . 
         [0025]    Referred back to  FIG. 3A  and  FIG. 3B , after the isolation groove  16  is formed, subsequently using one of ultraviolet laser light, green laser light, and infrared laser light to partially remove the back electrode layer  14  around an edge of the formed isolation groove  16  in the back electrode layer  14  such that the isolation groove  16  has a newly groove width in the back electrode layer  14  greater than that in the absorber layer  13  (as shown in  FIG. 3A ), or using one of green laser light and infrared laser light to partially remove both the back electrode layer  14  and the absorber layer  13  around an edge of the formed isolation groove  16  in the back electrode layer  14  such that the isolation groove  16  has a newly groove width in the absorber layer  13  (and/or back electrode layer  14 ) greater than that in the front electrode layer  12  (as shown in  FIG. 3B ). Please note that it is allowable that the back electrode layer  14  has a new groove width different than that of the absorber layer  13 . In any case described above of the third preferred embodiment, the defect  15  of the thin-film solar cell  10  is isolated so as to repair the defect  15  due to restraining its short-circuit effect and further to increase the overall power generation efficiency of the thin-film solar cell  10 . 
         [0026]    A method according to a fourth preferred embodiment of the present invention for defect isolation of a thin-film solar cell having a defect within a front electrode layer is shown in  FIG. 4A  and  FIG. 4B , where  FIG. 4A  is a sectional view of a thin-film solar cell  10  having a defect  15  isolated by an isolation groove having a first structure, and  FIG. 4B  is a sectional view of a thin-film solar cell  10  having a defect  15  isolated by an isolation groove having a second structure. A laser light device  24  is provided to emit infrared laser light for scribing along a closed curve centered around the defect  15  of the thin-film solar cell  10 , so that a back electrode layer  14 , an absorber layer  13  and a front electrode layer  12  of the thin-film solar cell  10  are all simultaneously partially removed to form an isolation groove  16  with a closed-curve configuration and a depth extending from the back electrode layer  14  through the absorber layer  13  to the front electrode layer  12 . 
         [0027]    Subsequently, one of ultraviolet laser light, green laser light, and infrared laser light is emitted along an edge of the formed isolation groove  16  to partially remove the back electrode layer  14  adjacent to the edge such that the isolation groove  16  has a newly groove width in the back electrode layer  14  greater than that in the absorber layer  13 , as shown in  FIG. 4A . 
         [0028]    Finally, one of green laser light and infrared laser light is emitted along an edge of the formed isolation groove  16  to further partially remove the absorber layer  13  adjacent to the edge such that the isolation groove  16  has a newly groove width in the absorber layer  13  greater than that in the front electrode layer  12 , as shown in  FIG. 4B . Please note that it is also applicable to partially remove both the back electrode layer  14  and the absorber layer  13  simultaneously such that the newly formed isolation groove  16  has an identical groove width respectively in the back electrode layer  14  and the absorber layer  13 , and the identical groove width is greater than that in the front electrode layer  12 . In any case described above of the fourth preferred embodiment, the defect  15  of the thin-film solar cell  10  is isolated. 
         [0029]    In the first, second, third, and fourth preferred embodiments of the present invention, the groove width of each isolation groove ranges from 0.001 μm to 100000 μm, and the closed-curve configurations of the isolation grooves can be any one of a rectangle, a triangle, a polygon, a circle, an ellipse, or an island shape. 
         [0030]    The present invention is described herein by reference to the preferred embodiments, and it is understood that the embodiments are not intended to limit the scope of the present invention. Moreover, as the contents disclosed herein should be readily understood and can be implemented by a person skilled in the art, all equivalent changes or modifications which do not depart from the spirit of the present invention should be encompassed by the appended claims.