Photovoltaic devices with metal semiconductor alloy metallization

Abstract

A photovoltaic device, such as a solar cell, having improved performance is provided. In one embodiment, the photovoltaic device includes a multimetal semiconductor alloy layer located on exposed portions of a front side surface of a semiconductor substrate. The multimetal semiconductor alloy layer includes at least a first elemental metal that forms an alloy with a semiconductor material, and a second elemental metal that differs from the first elemental metal and that does not form an alloy with a semiconductor material at the same temperature as the first elemental metal. The photovoltaic device further includes a copper-containing layer located atop the multimetal semiconductor alloy layer.

1 . A method of forming a photovoltaic device comprising:
 providing a semiconductor substrate including a p-n junction with a p-type semiconductor portion and an n-type semiconductor portion one on top of the other, wherein an upper exposed surface of one of the semiconductor portions represents a front side surface of the semiconductor substrate;   forming patterned antireflective coatings on the front side surface of the semiconductor substrate to provide a grid pattern on the front side surface, said grid pattern comprising exposed portions of the front side surface of the semiconductor substrate;   forming a multimetal semiconductor alloy layer on the exposed portions of the front side surface of the semiconductor substrate, wherein said multimetal semiconductor alloy layer comprises at least a first elemental metal that forms a semiconductor alloy at a first anneal temperature, and at least a second elemental metal that is different from the first elemental metal and does not form a metal semiconductor alloy at said first anneal temperature; and   electrodepositing a copper-containing layer atop the multimetal semiconductor alloy layer.   
     
     
         2 . The method of  claim 1 , wherein said forming the multimetal semiconductor alloy layer on the exposed portions of the front side surface of the semiconductor substrate comprises electrodepositing a multimetal layer including said first and second elemental metals and annealing at a temperature that is same as or greater than said first anneal temperature. 
     
     
         3 . The method of  claim 1 , wherein said first elemental metal is Ni and said second elemental metal is Co, Fe, Pt, Pd, W, Mo, Ag, Sn, Zn, or Ru. 
     
     
         4 . The method of  claim 1 , wherein said first elemental metal is Co and said second elemental metal is Fe, Pt, Pd, W, Mo, Ag, Sn, Zn, or Ru. 
     
     
         5 . The method of  claim 1 , wherein said multimetal semiconductor alloy layer has a ratio of the first elemental metal to the second elemental metal from 10000:1 to 1:100. 
     
     
         6 . The method of  claim 5 , wherein said multimetal semiconductor alloy layer has a ratio of the first elemental metal to the second elemental metal from 100:1 to 1:10. 
     
     
         7 . The method of  claim 1 , further comprising electrodepositing a metal diffusion barrier layer on an exposed upper surface of the multimetal semiconductor alloy layer prior to electrodepositing the copper containing layer. 
     
     
         8 . The method of  claim 7 , wherein the metal diffusion barrier layer comprises Ni, Co, P, S and any combination thereof. 
     
     
         9 . The method of  claim 1 , wherein said n-type semiconductor portion overlies said p-type semiconductor portion. 
     
     
         10 . The method of  claim 2 , wherein said temperature of said annealing is about 250° C. or greater. 
     
     
         11 . The method of  claim 7 , wherein said multimetal semiconductor alloy layer comprises Ni as said first elemental metal and Co, Fe, Pt, Pd, W, Mo, Ag, Sn, Zn, or Ru as said second elemental metal, said metal diffusion barrier layer comprises nickel, and said copper-containing layer comprises copper. 
     
     
         12 . The method of  claim 11 , wherein said second elemental metal is Co. 
     
     
         13 . The method of  claim 7 , wherein said multimetal semiconductor alloy layer comprises Ni as said first elemental metal and Co, Fe, Pt, Pd, W, Mo, Ag, Sn, Zn, or Ru as said second elemental metal, said metal diffusion barrier layer comprises cobalt, and said copper-containing layer comprises copper. 
     
     
         14 . The method of  claim 1 , wherein said multimetal semiconductor alloy layer comprises Co as said first elemental metal and Fe, Pt, Pd, W, Mo, Ag, Sn, Zn, or Ru as said second elemental metal, said metal diffusion barrier layer comprises Ni or Co, and said copper-containing layer comprises copper. 
     
     
         15 . A method of forming a photovoltaic device comprising:
 providing a semiconductor substrate including a p-n junction with a p-type semiconductor portion and an n-type semiconductor portion one on top of the other, wherein an upper exposed surface of one of the semiconductor portions represents a front side surface of the semiconductor substrate;   forming patterned antireflective coatings on the front side surface of the semiconductor substrate to provide a grid pattern on the front side surface, said grid pattern comprising exposed portions of the front side surface of the semiconductor substrate;   forming a multimetal layer on the exposed portions of the front side surface of the semiconductor substrate, wherein said multimetal layer comprises at least a first elemental metal that forms a semiconductor alloy at a first anneal temperature, and at least a second elemental metal that is different from the first elemental metal and does not form a metal semiconductor alloy at said first anneal temperature;   converting said multimetal layer into a single metal semiconductor alloy layer that consists of said first elemental metal and a semiconductor component;   electrodepositing a copper-containing layer atop the single metal semiconductor alloy layer.   
     
     
         16 . The method of  claim 15  wherein said multimetal layer has a ratio of said first elemental metal to said second elemental metal from 100:1 to 1:100.