Patent Publication Number: US-2023146692-A1

Title: Perc solar cell selective emitter, perc solar cell and manufacturing method therefor

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority to Chinese Patent Application No. 202011573167.9, entitled “PERC Solar Cell Selective Emitter, PERC Solar Cell and Manufacturing Method Therefor”, filed with China National Intellectual Property Administration on Dec. 25, 2020, the entire content of which is incorporated herein by reference. 
     TECHNICAL FIELD 
     The present application relates to the field of solar cells, and particularly to a PERC solar cell selective emitter, a PERC solar cell and a manufacturing method therefor. 
     BACKGROUND ART 
     In the manufacturing process of a solar cell, a selective emitter with a heavily doped region and a lightly doped region may be formed on the surface of a silicon wafer using a laser doping technology. However, in the laser doping process, the silicon wafer may be damaged by the sharp thermal action of laser, and the laser action position has serious compounding, which influences an open circuit voltage of the cell, and meanwhile damages the textured structure of the front surface and reduces absorption of a current, thus affecting an improvement of the cell efficiency. 
     SUMMARY 
     The present application provides a PERC solar cell selective emitter, a PERC solar cell and a manufacturing method therefor, which may reduce damage of laser to a silicon wafer and improve the cell efficiency. 
     Some embodiments of the present application provide a PERC solar cell selective emitter, which may include: a silicon wafer and first lightly doped regions, second lightly doped regions and a laser heavily doped region on the front surface of the silicon wafer; the laser heavily doped region includes a plurality of doped layers arranged at intervals in a preset direction; each doped layer includes a plurality of doped regions arranged at intervals; the first lightly doped regions are located between the doped regions of each doped layer, and each second lightly doped region is located between two adjacent doped layers. 
     Optionally, the laser heavily doped region and the first lightly doped region may have a total area of S, and the area of the laser heavily doped region and S may have a ratio of 1:10 to 9:10. 
     Optionally, the area of the laser heavily doped region and S may have a ratio of 2:5 to 3:5. 
     Optionally, the doped regions of two adjacent doped layers may be staggered. 
     Optionally, the silicon wafer may have a resistivity of 0.1 Ω*cm to 3.0 Ω*cm. 
     Further embodiments of the present application provide a PERC solar cell, which may include: a PERC solar cell selective emitter according to some embodiments of the present application, a front passivation layer on the surfaces of the first lightly doped region and the second lightly doped region, a front anti-reflective layer on the surface of the front passivation layer, and a positive electrode. 
     The positive electrode includes first silver paste layers on the surfaces of the laser heavily doped regions and second silver paste layers on the surface of the front anti-reflective layer corresponding to the first lightly doped regions, and the second silver paste layers are in electrical contact with the first silver paste layers. 
     Optionally, the front anti-reflective layer may be a silicon nitride layer, and the front passivation layer may be a silicon dioxide layer. 
     Optionally, the back surface of the PERC solar cell may be further provided with a back passivation layer and an aluminum back surface field, the back passivation layer may be formed on the back surface of the silicon wafer, the back passivation layer may be provided with a slot, and the aluminum back surface field may be formed on the surface of the back passivation layer and in the slot and in contact with the back surface of the silicon wafer. 
     Still further embodiments of the present application provide a manufacturing method for a PERC solar cell according to further embodiments of the present application, which may include: 
     diffusing on the surface of the textured silicon wafer to form a diffusion layer, and performing laser doping on the diffusion layer to form the laser heavily doped region, regions of the diffusion layer which are not subjected to laser doping being lightly doped regions, and the lightly doped regions including the first lightly doped region and the second lightly doped region; 
     sequentially plating the surfaces of the laser heavily doped region and the lightly doped region with the front passivation layer and the front anti-reflective layer; and
 
plating the surface of the front anti-reflective layer corresponding to the laser heavily doped region with the first silver paste layer, and burning through the front anti-reflective layer and the front passivation layer, such that the first silver paste layer is in contact with the laser heavily doped region, and plating the surface of the front anti-reflective layer corresponding to the first lightly doped region with the second silver paste layer, the second silver paste layer being in electrical contact with the first silver paste layer.
 
     Optionally, the back passivation layer is formed on the back surface of the silicon wafer, the back passivation layer is slotted, the aluminum back surface field is formed on the surface of the back passivation layer and in the slot, and the aluminum back surface field is in contact with the back surface of the silicon wafer. 
     Optionally, paste of the first silver paste layer may contain 5 wt % to 10 wt % of oxide, paste of the second silver paste layer may contain 0 wt % to 2 wt % of oxide, and the oxide may include at least one of PbO, B 2 O 3 , SiO 2 , BiO 3 , and ZnO. 
     Optionally, the paste of the first silver paste layer and the paste of the second silver paste layer may each contain 60 wt % to 90 wt % of silver powder. 
     Optionally, the silver powder may have a particle size of 0.1 μm to 4 μm. 
     Optionally, the paste of the first silver paste layer and the paste of the second silver paste layer may further contain organic carriers, and the organic carriers may include a thickener, a solvent, a surfactant, and a thixotropic agent. 
     Optionally, the paste of the first silver paste layer and the paste of the second silver paste layer may contain 10 wt % to 30 wt % of organic carriers. 
     The PERC solar cell selective emitter, the PERC solar cell and the manufacturing method therefor according to the embodiments of the present application at least have the beneficial effects as follows. 
     The laser heavily doped region of the PERC solar cell is a laser processed part, the first and second lightly doped regions are parts which are not processed by laser, the first lightly doped region is located between the doped regions of each doped layer, the first silver paste layer may burn through the front anti-reflective layer and the front passivation layer to be in contact with the laser heavily doped region to form good ohmic contact, the second silver paste layer does not burn through the front anti-reflective layer and the front passivation layer to be formed on the surface of the front anti-reflective layer corresponding to the first lightly doped region, and the second silver paste layer is in electrical contact with the first silver paste layer to achieve effects of connection and current leading-out. Compared with the solution that the doped regions are continuously arranged, in the embodiments of the present application, laser doped regions are relatively small, thus reducing damage of laser to the silicon wafer, and reducing surface compounding of the silicon wafer and damage of the laser to a textured surface. When the doped regions are continuously arranged, the silver paste layer is required to burn through the front passivation layer to be in contact with the silicon wafer; compared with the solution that the silver paste layer is in complete contact with the silicon wafer, in the embodiments of the present application, the second silver paste layer is only in contact with the first silver paste layer and not in contact with the silicon wafer, resulting in low series resistance. The arrangement of the laser heavily doped region and the arrangement of the first and second silver paste layers of the PERC solar cell according to the embodiments of the present application improve the cell efficiency. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       To describe the technical solutions in the embodiments of the present application more clearly, the following briefly describes the accompanying drawings required in the embodiments. It should be understood that the following accompanying drawings show merely some embodiments of the present application and therefore should not be considered as limiting the scope, and a person of ordinary skill in the art may still derive other related drawings from these accompanying drawings without creative efforts. 
         FIG.  1    is a schematic structural diagram of a PERC solar cell selective emitter according to an embodiment of the present application; 
         FIG.  2    is a schematic diagram of an arrangement position of a heavily doped region, a first lightly doped region and a second lightly doped region in the embodiment of the present application; 
         FIG.  3    is a schematic diagram of another arrangement position of the heavily doped region, the first lightly doped region and the second lightly doped region in the embodiment of the present application; 
         FIG.  4    is a schematic structural diagram of a PERC solar cell according to an embodiment of the present application; 
         FIG.  5    shows a structure obtained after step S 2  of a manufacturing method for a PERC solar cell according to an embodiment of the present application; and 
         FIG.  6    shows a structure obtained after step S 3  of the manufacturing method for a PERC solar cell according to the embodiment of the present application. 
     
    
    
     Reference numerals:  100 —selective emitter;  10 —PERC solar cell;  11 —silicon wafer;  12 —diffusion layer;  121 —first lightly doped region;  122 —second lightly doped region;  13 —heavily doped region;  131 —doped layer;  1311 —doped region;  14 —front passivation layer;  15 —front anti-reflective layer;  161 —first silver paste layer;  162 —second silver paste layer;  17 —back passivation layer;  171 —back silicon nitride layer;  172 —back aluminum oxide layer;  18 —aluminum back surface field. 
     DETAILED DESCRIPTION OF EMBODIMENTS 
     The implementation of the present application will be described in detail below in conjunction with embodiments, but those skilled in the art would understand that the following embodiments are merely for illustrating the present application and should not be deemed as restriction of the present application. The embodiments in which specific conditions are not given are performed according to conventional conditions or conditions suggested by manufacturers. The reagents or instruments used in the present disclosure, the manufacturers of which are not indicated, are the commercially available conventional products. 
     In the manufacturing process of a solar cell, when a heavily doped region and a lightly doped region are formed on the surface of a silicon wafer using laser doping, the silicon wafer is prone to damage by the laser, and the cell efficiency tends to be influenced. The applicant finds through research that generally, continuous laser spots are adopted to perform laser doping on the position corresponding to a grid line region to form a heavily doped region, and during subsequent silver paste printing, in order to lead out a current, a silver paste layer is generally in contact with the whole doped region of the silicon wafer, resulting in large contact resistance. When researching this treatment mode, the applicant finds that since the laser spots for laser doping are continuous, the laser has large damage to the silicon wafer and a textured surface, current absorption may be reduced simultaneously, surface compounding of the silicon wafer is high, and an open circuit voltage of the cell is affected, which influences the cell efficiency; in addition, this treatment mode may cause large contact resistance, which also affects the cell efficiency. 
     Based on this, embodiments of the present application provide a PERC solar cell selective emitter  100 , a PERC solar cell  10  and a manufacturing method therefor, which may reduce damage of laser to a silicon wafer  11  and improve the cell efficiency. 
     The PERC solar cell selective emitter  100 , the PERC solar cell  10  and the manufacturing method therefor according to the embodiments of the present application are described specifically below. 
     Some embodiments of the present application provide a PERC solar cell selective emitter  100 , which may include: a silicon wafer  11  and first lightly doped regions  121 , second lightly doped regions  122  and a laser heavily doped region  13  on the front surface of the silicon wafer  11  (refer to  FIGS.  1  to  3   ). 
     The laser heavily doped region  13  may include a plurality of doped layers  131  arranged at intervals in a preset direction; each doped layer  131  may include a plurality of doped regions  1311  arranged at intervals; the first lightly doped regions  121  may be located between the doped regions  1311  of each doped layer  131 , and each second lightly doped region  122  may be located between two adjacent doped layers  131  (refer to  FIGS.  2  and  3   ). Exemplarily, as shown in  FIGS.  2  and  3   , the preset direction is a longitudinal direction, the plurality of doped layers  131  are arranged at intervals in the longitudinal direction, and the doped regions  1311  of each doped layer  131  are arranged at intervals in a transverse direction. Exemplarily, the first lightly doped region  121 , the second lightly doped region  122 , and the laser heavily doped region  13  are optionally doped with phosphorus or boron. 
     The laser heavily doped region  13  may be a laser processed part, the first and second lightly doped regions  121 ,  122  may be parts which are not processed by laser, and the first lightly doped region  121  may be located between the doped regions  1311  of each set of doped layers  131 . Compared with the solution that the doped regions  1311  are continuously arranged, in the embodiments of the present application, laser doped regions are relatively small, which may reduce damage of laser to the silicon wafer  11 , and reduce surface compounding of the silicon wafer  11  and damage of the laser to a textured surface, thereby improving the cell efficiency. 
     Exemplarily, the silicon wafer  11  may have a resistivity of 0.1 Ω*cm to 3.0 Ω*cm. The silicon wafer  11  with the resistivity in this range facilitates an increase of the cell efficiency of the PERC solar cell  10 . Optionally, the wafer  11  has a resistivity of 0.1 Ω*cm, 0.5 Ω*cm, 1 Ω*cm, 1.5 Ω*cm, 2 Ω*cm, 2.5 Ω*cm, or 3 Ω*cm. 
     Optionally, the laser heavily doped region  13  and the first lightly doped region  121  may have a total area of S, and the area of the laser heavily doped region  13  and S may have a ratio of 1:10 to 9:10. It should be noted that the area of the laser heavily doped region  13  refers to the sum of the areas of all the doped regions  1311 . The total area S refers to the total area of the plurality of doped layers  131  and the first lightly doped regions  121  between the doped regions  1311  of the plurality of doped layers  131 . 
     The applicant finds through research that when the area of the laser heavily doped region  13  and S may have a ratio of 1:10 to 9:10, the cell efficiency may be improved better. Exemplarily, the area of the laser heavily doped region  13  and S may have a ratio of any one of 1:10, 1:5, 3:10, 2:5, 1:2, 3:5, 7:10, 4:5 and 9:10 or a range between any two therefrom. Exemplarily, the area of the laser heavily doped region  13  and S may have a ratio of 2:5 to 3:5. 
     Optionally, the doped regions  1311  of two adjacent doped layers  131  may be staggered (refer to  FIG.  3   ). The applicant finds through research that such an arrangement may better improve the cell efficiency. It may be understood that the stagger means that the doped regions  1311  of two adjacent doped layers  131  may not be overlapped or may be partially overlapped, and the overlapped part is less than 50% of the length of the doped region  1311 . It may be understood that the doped regions  1311  of two adjacent sets of doped layers  131  may be aligned (refer to  FIG.  2   ). 
     Referring to  FIG.  4   , further embodiments of the present application provide a PERC solar cell  10 , which may include: a PERC solar cell selective emitter  100  according to some embodiments of the present application, a positive electrode, a front passivation layer  14  on the surfaces of the first lightly doped region  121  and the second lightly doped region  122 , and a front anti-reflective layer  15  on the surface of the front passivation layer  14 . 
     The positive electrode may include first silver paste layers  161  on the surfaces of the laser heavily doped regions  13  and second silver paste layers  162  on the surface of the front anti-reflective layer  15  corresponding to the first lightly doped regions  121 , and the second silver paste layers  162  are in electrical contact with the first silver paste layers  161 . 
     The second silver paste layer  162  is in electrical contact with the first silver paste layer  161  to achieve effects of connection and current leading-out. Compared with the solution that the silver paste layer is in complete contact with the silicon wafer  11 , in the embodiments of the present application, the second silver paste layer  162  is only in contact with the first silver paste layer  161  and not in contact with the silicon wafer  11 , which results in low series resistance, thereby improving the cell efficiency. 
     Exemplarily, the front anti-reflective layer  15  may be a silicon nitride layer, and the front passivation layer may be a silicon dioxide layer. 
     The back surface of the PERC solar cell  10  may be further provided with a back passivation layer  17  and an aluminum back surface field  18 , the back passivation layer  17  may be formed on the back surface of the silicon wafer  11 , the back passivation layer  17  may be provided with a slot, and the aluminum back surface field  18  may be formed on the surface of the back passivation layer  17  and in the slot and in contact with the back surface of the silicon wafer  11 . Optionally, the back passivation layer  17  includes a back silicon nitride layer  171  and a back aluminum oxide layer  172 , the back aluminum oxide layer  172  is formed on the back surface of the silicon wafer  11 , and the back silicon nitride layer  171  is formed on the surface of the back aluminum oxide layer  172 . 
     Still further embodiments of the present application provide a manufacturing method for a PERC solar cell  10  according to some embodiments of the present application, which may include: 
     S 1 : diffusing on the surface of the textured silicon wafer  11  to form a diffusion layer  12 , and performing laser doping on the diffusion layer  12  to form the laser heavily doped region  13 , regions of the diffusion layer  12  which are not subjected to laser doping being lightly doped regions, and the lightly doped regions including the first lightly doped region  121  and the second lightly doped region  122 . The laser heavily doped region  13  may include the plurality of doped layers  131  arranged at intervals in the preset direction; each doped layer  131  may include the plurality of doped regions  1311  arranged at intervals; the first lightly doped regions  121  may be located between the doped regions  1311  of each doped layer  131 , and each second lightly doped region  122  may be located between two adjacent doped layers  131  (refer to  FIGS.  1  to  3   ). 
     S 2 : sequentially plating the surfaces of the laser heavily doped region  13  and the lightly doped region with the front passivation layer  14  and the front anti-reflective layer  15  (refer to  FIG.  5   ). 
     S 3 : plating the surface of the front anti-reflective layer  15  corresponding to a laser heavily doped layer  131  region with the first silver paste layer  161 , and burning through the front anti-reflective layer  15  and the front passivation layer  14 , such that the first silver paste layer  161  is in contact with the laser heavily doped layer  131  region, and plating the surface of the front anti-reflective layer  15  corresponding to the first lightly doped region  121  with the second silver paste layer  162 , the second silver paste layer  162  being in electrical contact with the first silver paste layer  161  (refer to  FIG.  6   ). 
     The laser heavily doped region  13  of the PERC solar cell  10  may be a laser processed part, the first and second lightly doped regions  121 ,  122  may be parts which are not processed by laser, the first silver paste layer  161  may burn through the front anti-reflective layer  15  and the front passivation layer  14  to be in contact with the laser heavily doped region  13  to form good ohmic contact, the second silver paste layer  162  does not burn through the front anti-reflective layer  15  and the front passivation layer  14  to be formed on the surface of the front anti-reflective layer  15  corresponding to the first lightly doped region  121 , and the second silver paste layer  162  is in electrical contact with the first silver paste layer  161  to achieve the effects of connection and current leading-out. Compared with the solution that the doped regions  1311  are continuously arranged, in the embodiments of the present application, the laser doped regions are relatively small, which may reduce damage of laser to the silicon wafer  11 , thereby improving the cell efficiency. Compared with the solution that the silver paste layer is in complete contact with the silicon wafer  11 , in the embodiments of the present application, the second silver paste layer  162  is only in contact with the first silver paste layer  161  and not in contact with the silicon wafer  11 , which results in low series resistance, thereby improving the cell efficiency. 
     Exemplarily, the laser for laser doping may have a frequency of 10 KHZ to 1,000 KHZ and a band speed of 1,000 m/h to 300,000 m/h. Optionally, the laser has a frequency of 10 KHZ, 30 KHZ, 50 KHZ, 100 KHZ, 200 KHZ, 400 KHZ, 500 KHZ, 800 KHZ, or 1,000 KHZ. Optionally, the laser has a band speed of any one of 1,000 m/h, 3,000 m/h, 5,000 m/h, 8,000 m/h, 10,000 m/h, 30,000 m/h, 50,000 m/h, 80,000 m/h, 100,000 m/h, 200,000 m/h, and 300,000 m/h or a range between any two therefrom. It may be understood that the laser band speed refers to the length swept by the laser in unit time. 
     Optionally, paste of the first silver paste layer  161  contains 5 wt % to 10 wt % of oxide, paste of the second silver paste layer  162  contains 0 wt % to 2 wt % of oxide, and the oxide includes at least one of PbO, B 2 O 3 , SiO 2 , BiO 3 , and ZnO. 
     The paste of the first silver paste layer  161  contains 5 wt % to 10 wt % of oxide which may include at least one of PbO, B 2 O 3 , SiO 2 , BiO 3 , and ZnO, and the oxide may burn through the front passivation layer  14  and the front anti-reflective layer  15  during sintering, such that the passivation effect is reduced; the front passivation layer  14  and the front anti-reflective layer  15  are burnt through by the oxide, such that the first silver paste layer  161  is in contact with the laser heavily doped region  13 , thus leading out the current. Paste of the second silver paste layer  162  may contain a small amount of oxide or may not contain the oxide, and the second silver paste layer  162  does not damage the front passivation layer  14  and the front anti-reflective layer  15 , thus not only achieving the effects of connection and current leading-out, but also achieving the effect of increasing the open circuit voltage. 
     Exemplarily, the paste of the first silver paste layer  161  may contain 5 wt %, 6 wt %, 7 wt %, 8 wt %, 9 wt %, or 10 wt % of oxide. Exemplarily, the paste of the second silver paste layer  162  may contain 0.1 wt %, 0.3 wt %, 0.5 wt %, 0.7 wt %, 1 wt %, 1.2 wt %, 1.5 wt %, 1.7 wt %, or 2 wt % of oxide. Optionally, the paste of the second silver paste layer  162  may not contain the above-mentioned oxide. 
     Optionally, the paste of the first silver paste layer  161  and the paste of the second silver paste layer  162  may each contain 60 wt % to 90 wt % of silver powder. The paste of the first silver paste layer  161  and the second silver paste layer  162  has high silver powder content, thus achieving a good conductive effect. Exemplarily, the paste in the first silver paste layer  161  may contain 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, or 90 wt % of silver powder. Exemplarily, the paste in the second silver paste layer  162  may contain 60 wt %, 65 wt %, 70 wt %, 75 wt %, 80 wt %, 85 wt %, or 90 wt % of silver powder. 
     Exemplarily, the silver powder may have a particle size of 0.1 μm to 4 μm. The silver powder with the particle size in this range facilitates adherence to the surface of the laser heavily doped layer  131  region and the surface of the first lightly doped region  121 . Optionally, the silver powder has a particle size of 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 2 μm, 3 μm, or 4 μm. 
     The paste of the first silver paste layer  161  and the paste of the second silver paste layer  162  may further contain organic carriers, and the organic carriers may include a thickener, a solvent, a surfactant, and a thixotropic agent; exemplarily, the paste of the first silver paste layer  161  and the paste of the second silver paste layer  162  may have 10 wt % to 30 wt % of organic carriers. 
     The PERC solar cell selective emitter  100 , the PERC solar cell  10 , and the manufacturing method therefor according to the present application are further described in detail below with reference to embodiments. 
     Example 1 
     The present embodiment provides a PERC solar cell, and a manufacturing process therefor may include: 
     diffusing on the surface of a textured silicon wafer to form a diffusion layer, and performing laser doping on the diffusion layer to form a laser heavily doped region, regions of the diffusion layer which are not subjected to laser doping being lightly doped regions, the lightly doped regions including a first lightly doped region and a second lightly doped region, the laser heavily doped region including a plurality of doped layers arranged at intervals in the longitudinal direction, each doped layer including a plurality of doped regions arranged at intervals in the transverse direction, the first lightly doped regions being located between the doped regions of each doped layer, and each second lightly doped region being located between two adjacent doped layers. The doped regions of two adjacent sets of doped layers are aligned, the laser heavily doped region and the first lightly doped region have a total area of S, and the area of the laser heavily doped region and S have a ratio of 1:2. 
     The surfaces of the laser heavily doped region and the lightly doped region are sequentially plated with a front passivation layer and a front anti-reflective layer. 
     The surface of the front anti-reflective layer corresponding to a laser heavily doped layer region is plated with a first silver paste layer, and the front anti-reflective layer and the front passivation layer are burnt through, such that the first silver paste layer is in contact with the laser heavily doped region; and the surface of the front anti-reflective layer corresponding to the first lightly doped region is plated with a second silver paste layer, the second silver paste layer being in electrical contact with the first silver paste layer. 
     A back passivation layer is formed on the back surface of the silicon wafer, the back passivation layer is slotted, an aluminum back surface field is formed on the surface of the back passivation layer and in the slot, the aluminum back surface field is in contact with the back surface of the silicon wafer, and the formed PERC solar cell is shown in  FIG.  4   . 
     Example 2 
     The present embodiment provides a PERC solar cell, and a manufacturing process thereof is substantially the same as the manufacturing process in Example 1 except that the doped regions of two adjacent sets of doped layers in the present embodiment are staggered (refer to  FIG.  3   ). 
     Example 3 
     The present embodiment provides a PERC solar cell, and a manufacturing process thereof is substantially the same as the manufacturing process in Example 1 except that the area of the laser heavily doped region and S have a different ratio which is 1:9. 
     Example 4 
     The present embodiment provides a PERC solar cell, and a manufacturing process thereof is substantially the same as the manufacturing process in Example 1 except that the area of the laser heavily doped region and S have a different ratio which is 2:3. 
     Example 5 
     The present embodiment provides a PERC solar cell, and a manufacturing process thereof is substantially the same as the manufacturing process in Example 1 except that the area of the laser heavily doped region and S have a different ratio which is 0.5:9.5. 
     Comparative Example 1 
     The comparative example provides a PERC solar cell, and a manufacturing process therefor includes: 
     diffusing on the surface of a textured silicon wafer to form a diffusion layer, and performing laser doping on the diffusion layer to form a laser heavily doped region, regions of the diffusion layer which are not subjected to laser doping being lightly doped regions, the laser heavily doped region including a plurality of doped layers which are arranged at intervals in the vertical direction, and each doped layer being composed of continuously arranged doped regions. 
     The surfaces of the laser heavily doped region and the lightly doped region are sequentially plated with a front passivation layer and a front anti-reflective layer. 
     The surface of the front anti-reflective layer corresponding to the laser heavily doped region is plated with a first silver paste layer, and the front anti-reflective layer and the front passivation layer are burnt through, such that the first silver paste layer is in contact with the laser heavily doped region. The first silver paste layer has same paste as the first silver paste layer in the first embodiment. 
     A back passivation layer is formed on the back surface of the silicon wafer, the back passivation layer is slotted, an aluminum back surface field is formed on the surface of the back passivation layer and in the slot, and the aluminum back surface field is in contact with the back surface of the silicon wafer. 
     Test Example 1 
     Open circuit voltages, short circuit currents, filling factors and conversion efficiencies of the PERC solar cells  10  manufactured according to Example 1-Example 5 and Comparative Example 1 were tested at 25° C. under AM 1.5 and 1 standard sun using a halm online I-V test system, and results are shown in table 1. 
     
       
         
           
               
             
               
                 TABLE 1 
               
             
            
               
                   
               
               
                 Performance test results of PERC solar cells 10 
               
               
                 of Example 1-Example 5 and Comparative Example 1 
               
            
           
           
               
               
               
               
               
            
               
                   
                 Open circuit 
                 Short circuit 
                 Filling 
                 Conversion 
               
               
                   
                 voltage 
                 current 
                 factor 
                 efficiency 
               
               
                   
                 (Voc)/V 
                 (Isc)/A 
                 (FF)/% 
                 (Eff)/% 
               
               
                   
                   
               
            
           
           
               
               
               
               
               
            
               
                 Example 1 
                 0.6815 
                 9.882 
                 82.28 
                 22.65 
               
               
                 Example 2 
                 0.6816 
                 9.883 
                 82.35 
                 22.68 
               
               
                 Example 3 
                 0.6828 
                 9.889 
                 82.01 
                 22.60 
               
               
                 Example 4 
                 0.6805 
                 9.878 
                 82.38 
                 22.62 
               
               
                 Example 5 
                 0.6831 
                 9.892 
                 81.87 
                 22.56 
               
               
                 Comparative 
                 0.6796 
                 9.854 
                 82.04 
                 22.57 
               
               
                 Example 1 
               
               
                   
               
            
           
         
       
     
     From the results of table 1, the PERC solar cell according to Example 1 has a better open circuit voltage, short circuit current, filling factor, and cell efficiency than the PERC solar cell in Comparative Example 1. After comparison of the results of Examples 1-4 and Example 5, the conversion efficiencies of the PERC solar cells according to Examples 1-4 are better than the conversion efficiency of the PERC solar cell according to Example 5, which shows that the ratios of the area of the laser heavily doped region to S in Examples 1˜4 of the present application better facilitate an improvement of the conversion efficiency of the PERC solar cell. 
     The above description is only specific embodiments of the present application and is not intended to limit the present application, and various modifications and changes may be made to the present application by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present application shall be included in the protection scope of the present application. 
     INDUSTRIAL APPLICABILITY 
     The present application provides the PERC solar cell selective emitter, the PERC solar cell and the manufacturing method therefor. The selective emitter includes the silicon wafer, the first lightly doped regions, the second lightly doped regions and the laser heavily doped region; the laser heavily doped region includes the plurality of doped layers; each doped layer includes the plurality of doped regions arranged at intervals; the first lightly doped regions are located between the doped regions of each doped layer, and each second lightly doped region is located between two adjacent doped layers. The PERC solar cell includes the selective emitter, the front anti-reflective layer on the surface of the front passivation layer, and the positive electrode. The positive electrode includes the first silver paste layers on the surfaces of the laser heavily doped regions and the second silver paste layers on the surface of the front anti-reflective layer corresponding to the first lightly doped regions, and the second silver paste layers are in electrical contact with the first silver paste layers. Damage of the laser to the silicon wafers is reduced, compounding in silver paste areas is reduced, the open circuit voltage is increased, and the cell efficiency is improved. 
     Furthermore, it may be understood that the PERC solar cell selective emitter, the PERC solar cell and the manufacturing method therefor according to the present application are reproducible and may be used in various industrial applications. For example, the PERC solar cell selective emitter, the PERC solar cell and the manufacturing method therefor according to the present application may be applied to the field of solar cells.