Use of dopants with different diffusivities for solar cell manufacture

Abstract

A method of tailoring the dopant profile of a substrate by utilizing two different dopants, each having a different diffusivity is disclosed. The substrate may be, for example, a solar cell. By introducing two different dopants, such as by ion implantation, furnace diffusion, or paste, it is possible to create the desired dopant profile. In addition, the dopants may be introduced simultaneously, partially simultaneously, or sequentially. Dopant pairs preferably consist of one lighter species and one heavier species, where the lighter species has a greater diffusivity. For example, dopant pairs such as boron and gallium, boron and indium, phosphorus and arsenic, and phosphorus and antimony, can be utilized.

1 . A method of creating a desired dopant profile in a solar cell, comprising:
 selectively implanting a first dopant and a second dopant at least partially simultaneously into a region of a surface of said solar cell using patterned ion implantation, wherein said region is less than an entirety of said surface and wherein said second dopant has a similar conductivity and higher diffusivity than said first dopant; and   performing a thermal cycle to diffuse said first dopant and said second dopant into said solar cell, wherein said second dopant diffuses deeper into said solar cell than said first dopant; and   applying contacts to said solar cell, wherein said contacts are applied to said region with high concentration of said first dopant.   
     
     
         2 . The method of  claim 1 , wherein said first dopant and said second dopant are selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, bismuth, boron, aluminum, gallium, and indium. 
     
     
         3 . The method of  claim 1 , wherein a flood implant is performed. 
     
     
         4 . The method of  claim 1 , wherein said first dopant is arsenic and said second dopant is phosphorus. 
     
     
         5 . The method of  claim 1 , wherein said first dopant is gallium and said second dopant is boron. 
     
     
         6 . The method of  claim 1 , wherein said patterned ion implantation comprises implanting through a stencil mask. 
     
     
         7 . A method of creating a desired dopant profile in a solar cell, comprising:
 selectively implanting a first dopant and a second dopant at least partially simultaneously into a region of a surface of said solar cell through a stencil mask, wherein said region is less than an entirety of said surface and wherein said second dopant has a similar conductivity and higher diffusivity than said first dopant; and   performing a thermal cycle to diffuse said first dopant and said second dopant into said solar cell, wherein said second dopant diffuses deeper into said solar cell than said first dopant; and   applying contacts to said solar cell, wherein said contacts are applied to said region with high concentration of said first dopant.   
     
     
         8 . The method of  claim 7 , wherein said first dopant and said second dopant are selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, bismuth, boron, aluminum, gallium, and indium. 
     
     
         9 . The method of  claim 7 , wherein a flood implant is performed. 
     
     
         10 . The method of  claim 7 , wherein said first dopant is arsenic and said second dopant is phosphorus. 
     
     
         11 . The method of  claim 7 , wherein said first dopant is gallium and said second dopant is boron. 
     
     
         12 . A method of creating a desired dopant profile in a solar cell, comprising:
 selectively implanting a first dopant and a second dopant at least partially simultaneously into a region of a surface of said solar cell using patterned ion implantation, wherein said region is less than an entirety of said surface and wherein said second dopant has a similar conductivity and higher diffusivity than said first dopant, wherein said region with high concentration of said first dopant is configured for use with contacts on said solar cell.   
     
     
         13 . The method of  claim 12 , wherein said first dopant and said second dopant are selected from the group consisting of nitrogen, phosphorus, arsenic, antimony, bismuth, boron, aluminum, gallium, and indium. 
     
     
         14 . The method of  claim 12 , wherein a flood implant is performed. 
     
     
         15 . The method of  claim 12 , wherein said first dopant is arsenic and said second dopant is phosphorus. 
     
     
         16 . The method of  claim 12 , wherein said first dopant is gallium and said second dopant is boron. 
     
     
         17 . The method of  claim 12 , wherein said patterned ion implantation comprises implanting through a stencil mask. 
     
     
         18 . The method of  claim 12 , further comprising: performing a thermal cycle to diffuse said first dopant and said second dopant into said solar cell, wherein said second dopant diffuses deeper into said solar cell than said first dopant; and
 applying contacts to said solar cell, wherein said contacts are applied to said region with high concentration of said first dopant.