Integrated thin film solar cell interconnection

Abstract

Photovoltaic modules may include multiple flexible thin film photovoltaic cells electrically connected in series, and laminated to a substantially transparent top sheet having a conductive grid pattern facing the cells. Methods of manufacturing photovoltaic modules including integrated multi-cell interconnections are provided. Methods may include steps of coordinating, integrating, and registering multiple rolls of substrates in continuous processes.

What is claimed is: 
     
         1 . A method of manufacturing a photovoltaic module, comprising:
 applying a photoactive composition to a conductive substrate in a roll-to-roll process, to produce a continuous sheet of photovoltaic material;   cutting the continuous sheet of photovoltaic material into a plurality of discrete reels;   cutting each reel into a plurality of discrete photovoltaic cells;   removing photoactive composition from a first cell to create an interconnection area of the first cell that is electrically isolated from the photoactive composition disposed outside the interconnection area;   placing the first photovoltaic cell and a second photovoltaic cell in contact with an optically transmissive top sheet and thereby placing a conductive grid pattern of the top sheet into electrical contact with portions of the photoactive composition of each photovoltaic cell, including portions of the photoactive composition of the first photovoltaic cell within the interconnection area;   heat staking the first and second cells to the top sheet to hold the photovoltaic cells in fixed positions relative to the top sheet;   laser welding the top sheet to a portion of the interconnection area of the first photovoltaic cell by directing a laser to impinge first on a back side of the substrate of the first photovoltaic cell, thereby electrically interconnecting the photovoltaic cells;   placing a bottom sheet adjacent to the substrate of the photovoltaic cells and to edge portions of the top sheet; and   laminating the top sheet and the bottom sheet to the photovoltaic cells.   
     
     
         2 . The method of  claim 1 , wherein removing photoactive composition from the photovoltaic material includes laser scribing a perimeter portion of the interconnection area. 
     
     
         3 . The method of  claim 2 , further comprising laser scribing a perimeter portion of each photovoltaic cell. 
     
     
         4 . The method of  claim 1 , wherein placing the first photovoltaic cell and the second photovoltaic cell in contact with the top sheet includes leaving an exposed area of each cell extending beyond the grid pattern of the top sheet. 
     
     
         5 . The method of  claim 1 , wherein the top sheet includes an adhesive layer disposed upon a structural layer. 
     
     
         6 . The method of  claim 1 , wherein the photoactive composition includes a p-type semiconductor layer formed of copper indium gallium diselenide (CIGS), and an n-type semiconductor layer formed of cadmium sulfide (CdS). 
     
     
         7 . The method of  claim 1 , further comprising irradiating the photovoltaic cells and measuring a voltage induced between a top and a bottom side of each photovoltaic cell. 
     
     
         8 . A method of manufacturing a photovoltaic module, comprising:
 applying a photoactive composition to a conductive substrate in a roll-to-roll process, to produce a continuous sheet of flexible photovoltaic material;   cutting the photovoltaic material, including the conductive substrate, into first and second photovoltaic cells;   laser scribing through the photoactive composition of the first photovoltaic cell to form an interconnection region which is electrically isolated from the photoactive composition of the first photovoltaic cell surrounding the interconnection region;   providing a frontsheet including a conductive pattern disposed on an optically transparent polymer sheet, the conductive pattern including first and second electrically isolated collection grid sections and an interconnection section extending from the second collection grid section;   positioning the first and second photovoltaic cells on the frontsheet so that a top surface of the photoactive composition of the second photovoltaic cell makes electrical contact with the second collection grid section, and the interconnection region of the first photovoltaic cell makes electrical contact with the interconnection section extending from the second collection grid section; and   laser welding the frontsheet to the interconnection region, by directing a laser to impinge first on a back side of the conductive substrate of the first photovoltaic cell, to form an electrical connection between the interconnection section extending from the second collection grid section and the conductive substrate of the first photovoltaic cell, and thus between the conductive substrate of the first photovoltaic cell and the top surface of the photoactive composition of the second photovoltaic cell.   
     
     
         9 . The method of  claim 8 , wherein the second collection grid section includes a buss bar and the interconnection section extends from the buss bar, and further comprising applying a dielectric strip to cover the buss bar without covering the interconnection section, before positioning the photovoltaic cells on the frontsheet. 
     
     
         10 . The method of  claim 9 , wherein positioning the photovoltaic cells on the frontsheet includes positioning a leading edge of the first photovoltaic cell overlapping the dielectric strip and positioning a trailing edge of the second photovoltaic cell overlapping the dielectric strip, to form a gap between the first photovoltaic cell and the second photovoltaic cell. 
     
     
         11 . The method of  claim 8 , further comprising forming a preliminary adhesive attachment between the photovoltaic cells and the conductive pattern of the frontsheet, prior to laser welding the frontsheet to the interconnection region. 
     
     
         12 . The method of  claim 11 , wherein forming the preliminary adhesive attachment is performed by heat staking the photovoltaic cells to the frontsheet. 
     
     
         13 . The method of  claim 8 , wherein cutting the photovoltaic material into first and second photovoltaic cells includes cutting the continuous sheet of photovoltaic material into a plurality of reels of photovoltaic material, each reel having a width corresponding to a desired width of the photovoltaic cells and a length exceeding a desired length of the photovoltaic cells, and then cutting each reel of photovoltaic material into a plurality of discrete photovoltaic cells each having the desired width and the desired length. 
     
     
         14 . The method of  claim 8 , further comprising laminating a protective backsheet to the conductive substrate of the photovoltaic cells and to edge portions of the frontsheet which extend beyond edges of the photovoltaic cells. 
     
     
         15 . A method of assembling a photovoltaic module, comprising:
 providing first and second discrete, physically separate photovoltaic cells, each including a conductive substrate covered by a photoactive composition;   removing photoactive composition from a portion of the first photovoltaic cell to create an interconnection area that is electrically isolated from the photoactive composition disposed outside the interconnection area;   placing the first and second photovoltaic cells in contact with an optically transmissive top sheet and thereby placing a conductive grid pattern of the top sheet into electrical contact with portions of the photoactive composition of each photovoltaic cell, including a portion of the photoactive composition of the first photovoltaic cell within the interconnection area; and   directing a laser to impinge on a back side of the substrate of the first photovoltaic cell, thus electrically interconnecting the first and second photovoltaic cells by electrically connecting a portion of the grid pattern in electrical contact with the photoactive composition of the second photovoltaic cell to a portion of the substrate located within the interconnection area of the first photovoltaic cell.   
     
     
         16 . The method of  claim 15 , further comprising heat staking the first and second photovoltaic cells to the top sheet, prior to directing the laser to impinge on the back side of the substrate of the first photovoltaic cell. 
     
     
         17 . The method of  claim 15 , wherein removing photoactive composition from a portion of the first photovoltaic cell to create an interconnection area includes laser scribing a perimeter defining the interconnection area. 
     
     
         18 . The method of  claim 15 , further comprising irradiating the photovoltaic cells and measuring a voltage induced between a top and a bottom side of each photovoltaic cell, prior to placing the first and second photovoltaic cells in contact with the optically transmissive top sheet. 
     
     
         19 . The method of  claim 15 , further comprising testing the photovoltaic module to measure cell performance, after electrically interconnecting the first and second photovoltaic cells. 
     
     
         20 . The method of  claim 15 , further comprising laminating a protective backsheet to a bottom side of the first and second photovoltaic cells.