Patent Publication Number: US-2009229653-A1

Title: Stacked-layered thin film solar cell and manufacturing method thereof

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     The present invention relates to a stacked-layered thin film solar cell and a manufacturing method thereof. More particularly, the present invention relates to a stacked-layered thin film solar cell and a manufacturing method thereof wherein an outer groove and a cutting groove are implemented to prevent short-circuit faults. 
     2. Description of Related Art 
     Please refer to  FIGS. 1A and 1B  for a conventional stacked-layered thin film solar cell  1 , which comprises a substrate  14 , a first electrode layer  11 , a semi-conductor layer  13 , and a second electrode layer  12  in a series stacked structure. In a manufacturing process of such stacked-layered thin film solar cell  1 , the substrate  14  is firstly deposited with the first electrode layer  11  and then receives a laser scribing treatment so as to form a plurality of unit cells  112  and first grooves  111 . Then the first electrode layer  11  is deposited thereon with the semi-conductor layer  13 , and the semi-conductor layer  13  is such laser scribed that each semi-conductor scribed groove  131  is distant from a said scribed groove of the first electrode layer  11  for about 100 microns. Afterward, the semi-conductor layer  13  is deposited thereon with a second electrode layer  12 , and the second electrode layer  12  as well as the semi-conductor layer  13  are such laser scribed that each resultant scribed groove  121  is distant from a said semi-conductor scribed groove  131  for about 100 microns. By the foregoing deposited layers and laser scribing processes performed on each said layer, the stacked-layered thin film solar cell  1  composed of the unit cells  112  in serial is so established. 
     In a following packaging process, for eliminating problems about short-circuit faults and electric leakage, U.S. Pat. No. 6,300,556 proposes a method involving forming an isolation groove  15  by scribing the solar cell near a periphery thereof for partially removing the first electrode layer, the semi-conductor layer and the second electrode layer, and the mechanically removing the first electrode layer, the semi-conductor layer and the second electrode layer or films of the three layers outside the isolation groove  15  near a periphery of the substrate. Besides, the disclosure of U.S. Pat. No. 6,271,053 involves depositing the layers, dividing the deposited layers into serially connected solar cells, removing the second electrode layer and semi-conductor layer at peripheries of the cells so as to reveal the semi-conductor layer, and then thermally processing the revealed semi-conductor layer to oxidize its surface and thereby increase its resistance. Otherwise, US Patent Publication 2006/0,266,409 reveals the first electrode layer by removing the second electrode layer and the semi-conductor layer with a first laser before using a second laser to remove the second electrode layer, the semi-conductor layer and the first electrode layer elsewhere has been removed by the first laser. 
     In the above technology, for forming the isolation grooves, due to diverseness of the films, the first laser of a certain wavelength is used to remove the second electrode layer and the semi-conductor layer so as to form scribed grooves, and to repeatedly scribe the scribed isolation grooves to widen the same in order to enhance accurateness of a cutting process later performed on the first electrode layer. Afterward, the second laser of another wavelength is employed to cut the first electrode layer. Since the isolation grooves are formed by two types of laser beams of different wavelengths, the manufacturing procedures are complicated and therefore equipment costs as well as manufacturing cycle are enlarged. Furthermore, after the cutting process is performed, due to possible unevenness of the laser beams, part of the second electrode layer may be not fully removed and, in its melt state, remains on the first electrode layer, leading to short-circuit faults. Though using a single type of laser in length to process the three layers facilitates simplifying the manufacturing procedures, it is notable that the resultant thermal effect is greater and thus the induced short-circuit problem is more significant. Moreover, when thermal treatment is implemented at the late stage of the manufacturing procedures to oxidize the semi-conductor layer and thereby increase its resistance for averting the short-circuit problem, equipment costs and manufacturing cycle can be accordingly increased. 
     On the other hand, due to recombination of electrons and holes and loss of light, photoelectric conversion efficiency in a stacked-layered thin film solar cell is limited. Thus, an interlayer is usually arranged between a material of a higher energy level and another material of a lower energy level so that when light passes through the stacked-layered thin film solar cell, a portion of the light having short wavelengths that can be absorbed by the material of the higher energy level is reflected to extend a light path while a portion of the light having long wavelengths that can not be absorbed by the material of the higher energy level is led to the material of the lower energy level so as to improve light transmission. For example, U.S. Pat. No. 5,021,100 proposes a dielectric selective reflection film in a stacked-layered thin film solar cell. Since the interlayer, for connecting materials of different energy levels, possesses electric conductivity, electric leakage and short-circuit faults can easily happen during an edge isolating process of the interlayer. Therefore, U.S. Pat. No. 6,632,993 further provides cutting grooves  161  scribed on the interlayer  16  for eliminating electric leakage when a current passes through the interlayer  16 , as shown in  FIG. 1C . U.S. Pat. No. 6,870,088 also suggests a similar approach but further provides scribed grooves  181  on a photoelectric conversion layer  18  between cutting grooves  171 , as shown in  FIG. 1D , so as to eliminate the above-mentioned problems. However, all of theses conventional approaches fail to address solutions to short-circuit faults at the edge of the battery. 
     SUMMARY OF THE INVENTION 
     In view of the defects of the conventional devices, the present invention provides a stacked-layered thin film solar cell and a manufacturing method thereof. The stacked-layered thin film solar cell with a plurality of unit cells comprises a substrate, a first electrode layer, a first photoconductive layer, an interlayer, a second photoconductive layer, and a second electrode layer in a series stacked structure. It is characterized in that a first isolation groove and a second isolation groove are formed on at least two borders of the second electrode layer. The first isolation groove and the second isolation groove are outside a projection zone of the unit cells and extending downward to remove the first photoconductive layer. The first isolation groove is parallel with the unit cells and vertical to the second isolation groove. At least one outer groove is formed on the first electrode layer inside the first isolation groove and the second isolation groove, and at least one cutting groove inside the first isolation groove is formed on the interlayer. 
     Hence, a primary objective of the present invention is to provide a stacked-layered thin film solar cell, which has a cutting groove and isolation grooves at borders thereof, so as to achieve improved isolating efficiency. 
     A secondary objective of the present invention is to provide a manufacturing method of a stacked-layered thin film solar cell, wherein the stacked-layered thin film solar cell has a cutting groove and isolation grooves at borders thereof, so as to achieve improved isolating efficiency. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention as well as a preferred mode of use, further objectives and advantages thereof, will best be understood by reference to the following detailed description of an illustrative embodiment when read in conjunction with the accompanying drawings, wherein: 
         FIGS. 1A and 1B  are schematic drawings showing a conventional stacked-layered thin film solar cell; 
         FIG. 1C  is a schematic drawing showing another conventional stacked-layered thin film solar cell; 
         FIG. 1D  is a schematic drawing showing yet another conventional stacked-layered thin film solar cell; and 
         FIGS. 2A through 2C  are schematic drawings showing a stacked-layered thin film solar cell according to a first preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     While the present invention discloses a stacked-layered thin film solar cell and a manufacturing method thereof, those skilled in the art will recognize and appreciate that the principle of solar photoelectric conversion implemented therein is well known and need not be discussed at any length herein. Meantime, the accompanying drawings for being read in conjunction with the following descriptions are aim to express features of the present invention and need not to be made in scale. 
     Please refer to  FIGS. 2A through 2C  for a first preferred embodiment of the present invention. Therein, a stacked-layered thin film solar cell  2  with a plurality of unit cells  212  comprises a substrate  20 , a first electrode layer  21 , a first photoconductive layer  23 , an interlayer  25 , a second photoconductive layer  24 , and a second electrode layer  22  in a series stacked structure. 
     The unit cells  212  may be electrically connected in series connection, in parallel connection or in series-parallel connection. Besides, the substrate  20  may be made of a transparent material. 
     For enhancing edge isolation of the battery so as to eliminate the short-circuit problem, referring to  FIG. 2A , a first isolation groove  261  and a second isolation groove  262  are formed on at least two borders of the second electrode layer  22 . The first isolation groove  261  and the second isolation groove  262  are outside a projection zone of the unit cells  212  and extending downward to remove the first photoconductive layer  23 . Alternatively, the first isolation groove  261  and the second isolation groove  262  can extend downward further to remove the first electrode layer  21 , as shown in  FIG. 2C . Therein, the first isolation groove  261  is parallel with the unit cells  212  and vertical to the second isolation groove  262 . The first isolation groove  261  or the second isolation groove  262  may have a width ranging from 20 microns to 200 microns. At least one outer groove  27  is formed on the first electrode layer  21  inside the first isolation groove  261  and the second isolation groove  262 . The outer groove  27  may have a width ranging from 20 microns to 200 microns. According to  FIG. 2A , after the interlayer  25  is formed, a cutting groove  29  may be further formed thereon to obstruct the conductivity of the interlayer  25 , and thus eliminate problems of electric leakage or short-circuit faults during an edge isolating process of the stacked-layered thin film solar cell  2 , thereby providing enhanced insulating efficiency while not increasing overall manufacturing costs. Alternatively, the cutting groove  29  can extend downward further to remove the first photoconductive layer  23 , as shown in  FIG. 2C . Therein, the cutting groove  29  may be formed inside the first isolation groove  261 , or may be formed inside or outside the outer groove  27 , or may overlap the outer groove  27 , wherein the cutting groove  29  is preferably formed outside the outer groove  27 . The cutting groove  29  may have a width ranging from 20 microns to 200 microns. 
     The first isolation groove  261 , the second isolation groove  262  and the cutting groove  29  may be formed by a laser scribing process, a wet etching process, or a dry etching process. 
     The first electrode layer  21  may be formed on the substrate  20  by a sputtering process, an APCVD (Atmospheric Pressure Chemical Vapor Deposition) process, or a LPCVD (Low Pressure Chemical Vapor Deposition) process. The first electrode layer  21  may have a single-layer structure or a multi-layer structure and may be made of a TCO (Transparent Conductive Oxide) comprising SnO2, ITO, ZnO, AZO, GZO or IZO. The first electrode layer  21  may further comprise a metal layer made of Ag, Al, Cr, Ti, Ni or Au. 
     The first photoconductive layer  23  may be formed on the first electrode layer  21  by a deposit process and made of single-crystal Si, multi-crystal Si, non-crystal Si, micro-crystal Si, Ge, SiGe and SiC. The interlayer  25  may be formed on the first photoconductive layer  23  by a deposit process and made of a material selected from TO, ITO, ZnO, AZO, GZO and IZO. The second photoconductive layer  24  may also be formed on the interlayer  25  by a deposit process with single-crystal Si, multi-crystal Si, non-crystal Si, micro-crystal Si, Ge, SiGe and SiC. 
     The second electrode layer  22  may be formed on the second photoconductive layer  24  by a sputtering process, or a PVD (Physical Vapor Deposition) process. The second electrode layer  22  may have a single-layer structure or a multi-layer structure and may be made of a TCO (Transparent Conductive Oxide) comprising SnO2, ITO, ZnO, AZO, GZO or IZO. The second electrode layer  22  may further comprise a metal layer made of Ag, Al, Cr, Ti, Ni, Au or an alloy of any of the above materials. 
     The present further provides a second preferred embodiment. Therein, a manufacturing method of a stacked-layered thin film solar cell  2 , for improving edge isolation of the stacked-layered thin film solar cell  2  and eliminating short-circuit faults, comprises steps of: 
     (1) providing a substrate  20 , a first electrode layer  21 , a first photoconductive layer  23 , an interlayer  25 , a second photoconductive layer  24 , and a second electrode layer  22  in a series stacked structure; 
     (2) providing a first isolation groove  261  and a second isolation groove  262  on at least two borders of the second electrode layer  22 , wherein a first isolation groove  261  and a second isolation groove  262  are outside a projection zone of the unit cells  212  and extending downward to remove the first photoconductive layer  23  while the first isolation groove  261  is parallel with the unit cells  212  and vertical to the second isolation groove  262 ; 
     (3) providing at least one outer groove  27  on the first electrode layer  21  inside the first isolation groove  261  and the second isolation groove  262 ; and 
     (4) providing at least one cutting groove  29  inside the first isolation groove  261  on the interlayer  25 . 
     In the manufacturing method of the present invention, the substrate  20 , the first electrode layer  21 , the first photoconductive layer  23 , the interlayer  25 , the second photoconductive layer  24 , and the second electrode layer  22 , the first isolation groove  261 , the second isolation groove  262 , the outer groove  27  and the cutting groove  29  share the same features of their resemblances described in the first embodiment. 
     Although the particular embodiments of the invention have been described in detail for purposes of illustration, it will be understood by one of ordinary skill in the art that numerous variations will be possible to the disclosed embodiments without going outside the scope of the invention as disclosed in the claims.