Solar cells with plated back side surface field and back side electrical contact and method of fabricating same

Abstract

The present disclosure provides a method of forming a back side surface field of a solar cell without utilizing screen printing. The method includes first forming a p-type dopant layer directly on the back side surface of the semiconductor substrate that includes a p/n junction utilizing an electrodeposition method. The p/n junction is defined as the interface that is formed between an n-type semiconductor portion of the substrate and an underlying p-type semiconductor portion of the substrate. The plated structure is then annealed to from a P++ back side surface field layer directly on the back side surface of the semiconductor substrate. Optionally, a metallic film can be electrodeposited on an exposed surface of the P++ back side surface layer.

1 . A solar cell comprising:
 a semiconductor substrate including a p-type semiconductor portion and an overlying n-type semiconductor portion, wherein an exposed surface of the p-type semiconductor portion defines a back side surface of the semiconductor substrate and wherein an exposed surface of the n-type semiconductor portion defines a front side surface; and   a P++ doped back side surface field layer located at the back side surface of said semiconductor substrate.   
     
     
         2 . The solar cell of  claim 1  wherein said semiconductor substrate comprises one of Si, Ge, SiGe, SiC, SiGeC, GaAs, GaN, InAs, InP and all other III/V and II/VI compound semiconductors. 
     
     
         3 . The solar cell of  claim 1  wherein said P++ doped back side surface field layer has a p-type dopant concentration from 1e19 atoms/cm 3  to 1e23 atoms/cm 3 . 
     
     
         4 . The solar cell of  claim 1  wherein said front side surface of the semiconductor substrate is textured. 
     
     
         5 . The solar cell of  claim 1  wherein said n-type semiconductor portion has a sheet resistance of greater than 50 ohm/sq. 
     
     
         6 . The solar cell of  claim 5  further comprising a metallic film located on an exposed surface of said P++ doped back side surface field layer. 
     
     
         7 . The solar cell of  claim 6  wherein said metallic film includes Ni, Co, Al, Ag, Au, Cu, Zn, Pt, Ag, Pd, Sn, Fe, In or alloys thereof. 
     
     
         8 . The solar cell of  claim 1  wherein said P++ doped back side surface field layer includes B or a B alloy. 
     
     
         9 . The solar cell of  claim 1  wherein said P++ doped back side surface field layer includes Ga or a Ga alloy. 
     
     
         10 . The solar cell of  claim 1  wherein said P++ doped back side surface field layer includes In or an InB alloy. 
     
     
         11 . The solar cell of  claim 1  wherein said P++ doped back side surface field layer includes Al or an Al alloy.