Fabrication process of solar cell

Abstract

Metal-grade silicon is melted and solidified in a mold to form a plate-shaped silicon layer and a crystalline silicon layer is made thereon, thereby providing a cheap solar cell without a need for a slicing step.

What is claimed is:  
     
         1 . A fabrication process of solar cell comprising a step of forming a silicon layer on a crystalline silicon substrate by a liquid-phase growth method using a metal solvent, wherein a total concentration of impurities of a surface of said crystalline silicon substrate is 10 ppm or more and wherein said metal solvent is indium.  
     
     
         2 . A fabrication process of solar cell according to  claim 1 , wherein said liquid-phase growth method is carried out in a hydrogen atmosphere.  
     
     
         3 . A fabrication process of solar cell according to  claim 1  or  2 , wherein said crystalline silicon substrate is comprised of metal-grade silicon containing 10 ppm or more of impurities.  
     
     
         4 . A fabrication process of solar cell comprising a step of melting and solidifying particles of metal-grade silicon put in a mold to form a plate-shaped metal-grade silicon substrate, and a step of forming a silicon layer on a surface of said metal-grade silicon substrate by a liquid-phase growth method using indium.  
     
     
         5 . A fabrication process of solar cell according to  claim 4 , wherein a material for said mold is selected from the group consisting of carbon graphite, silicon carbide, and silicon nitride.  
     
     
         6 . A fabrication process of solar cell according to  claim 4  or  5 , wherein a surface of said mold to be in contact with said metal-grade silicon substrate is coated with a mold releasing agent containing at least silicon nitride.  
     
     
         7 . A fabrication process of solar cell comprising a step of melting and solidifying particles of metal-grade silicon put in a mold to form a plate-shaped metal-grade silicon substrate, a step of dissolving a surface of said metal-grade silicon substrate with a metal solvent and thereafter precipitating silicon in said metal solvent on the surface of said metal-grade silicon substrate to form a first silicon layer, and a step of further forming a second silicon layer on a surface of said first silicon layer by a liquid-phase growth method using indium.  
     
     
         8 . A fabrication process of solar cell according to  claim 7  wherein a material for said mold is selected from the group consisting of carbon graphite, silicon carbide, and silicon nitride.  
     
     
         9 . A fabrication process of solar cell according to  claim 7  or  8 , wherein a surface of said mold to be in contact with said metal-grade silicon substrate is coated with a mold releasing agent containing at least silicon nitride.  
     
     
         10 . A fabrication process of solar cell according to  claim 7 , wherein said first silicon layer is p-type silicon containing 10 ppm to 100 ppm of impurities.  
     
     
         11 . A fabrication process of solar cell according to  claim 7 , wherein said metal solvent is selected from the group consisting of indium, gallium, and tin.  
     
     
         12 . A fabrication process of solar cell according to  claim 1 , wherein a thickness of said silicon layer is 10 μm or more.  
     
     
         13 . A fabrication process of solar cell according to  claim 7 , wherein a thickness of said silicon layer is 10 μm or more.