Bifacial solar cells with back surface doping

Abstract

A simplified manufacturing process and the resultant bifacial solar cell (BSC) are provided, the simplified manufacturing process reducing manufacturing costs. The BSC includes an active region located on the front surface of the substrate, formed for example by a phosphorous diffusion step. The back surface includes a doped region, the doped region having the same conductivity as the substrate but with a higher doping level. Contact grids are formed, for example by screen printing. Front junction isolation is accomplished using a laser scribe.

1 - 20 . (canceled) 
     
     
         21 . A method of fabricating a bifacial solar cell (BSC), the method comprising the steps of:
 depositing a boron doped layer on a back surface of a p-type silicon substrate;   depositing a back surface dielectric onto said boron doped layer;   diffusing phosphorous onto a front surface of said silicon substrate to form an n +  layer and a front surface junction;   removing a phosphor-silicate glass (PSG) formed during said phosphorous diffusing step;   depositing a front surface passivation and anti-reflection (AR) dielectric layer onto said n +  layer;   applying a back surface contact grid;   applying a front surface contact grid;   firing said back surface contact grid;   firing said front surface contact grid; and   isolating said front surface junction.   
     
     
         22 . The method of  claim 21 , wherein said step of applying said back surface contact grid further comprises the step of screen printing said back surface contact grid, and wherein said step of applying said front surface contact grid further comprises the step of screen printing said front surface contact grid. 
     
     
         23 . The method of  claim 21 , wherein said front surface junction isolating step further comprises the step of forming a groove on the front surface of the BSC with a laser scriber. 
     
     
         24 . The method of  claim 21 , wherein said steps of firing said back and front surface contact grids are performed simultaneously. 
     
     
         25 . The method of  claim 21 , wherein said step of firing said back surface contact grid is performed prior to said step of applying said front surface contact grid. 
     
     
         26 . The method of  claim 21 , wherein said boron doped layer depositing step further comprises the step of depositing a boron doped silicon dioxide layer using chemical vapor deposition. 
     
     
         27 . The method of  claim 21 , wherein said boron doped layer depositing step further comprises the step of depositing a boron doped silicon layer using chemical vapor deposition. 
     
     
         28 . The method of  claim 21 , wherein said boron doped layer depositing step further comprises the step of depositing a boron doped amorphous silicon layer using plasma enhanced chemical vapor deposition. 
     
     
         29 . The method of  claim 21 , wherein said boron doped layer depositing step further comprises the step of spraying a boric acid solution onto said back surface of said silicon substrate. 
     
     
         30 . The method of  claim 21 , wherein said boron doped layer depositing step further comprises the step of spraying a boron doped spin-on glass onto said back surface of said silicon substrate. 
     
     
         31 . The method of  claim 21 , wherein said PSG removing step further comprises the step of etching said front surface with a hydrofluoric etch. 
     
     
         32 . The method of  claim 21 , further comprising the step of selecting said dielectric from the group consisting of silicon nitride, silicon dioxide and silicon oxynitride. 
     
     
         33 . The method of  claim 21 , wherein said step of depositing said back surface dielectric onto said boron doped layer further comprises the step of depositing a dielectric stack onto said boron doped layer. 
     
     
         34 . The method of  claim 32 , further comprising the step of selecting materials for said dielectric stack from the group consisting of silicon nitride, silicon dioxide and aluminum oxide. 
     
     
         35 . The method of  claim 21 , wherein said phosphorous diffusing step is performed at a temperature of approximately 850° C. for a duration of approximately 10 to 20 minutes. 
     
     
         36 . The method of  claim 21 , further comprising the step of selecting said front surface passivation and AR dielectric layer from the group consisting of silicon nitride and silicon oxynitride.