TCOs for Heterojunction Solar Cells

Abstract

Methods are used to develop and evaluate new materials and deposition processes for use as TCO materials in HJCS solar cells. The TCO layers allow improved control over the uniformity of the TCO conductivity and interface properties, and reduce the sensitivity to the texture of the wafer. In Some embodiments, the TCO materials include indium, zinc, tin, and aluminum.

What is claimed: 
     
         1 . A method for forming a heterojunction solar cell on a substrate, the method comprising:
 forming a first layer above a first surface of the substrate, wherein the first layer comprises a p-doped amorphous silicon layer;   forming a second layer above the first layer, wherein the second layer comprises a metal oxide layer and wherein the second layer forms an ohmic contact to the first layer; and   forming a third layer above the second layer, wherein the third layer comprises a transparent conductive oxide layer, wherein the third layer comprises indium-tin-aluminum-zinc-oxide.   
     
     
         2 . The method of  claim 1  wherein the third layer comprises indium at a concentration between 50 and 90 weight %. 
     
     
         3 . The method of  claim 1  wherein the third layer comprises tin at a concentration between 2 and 8 weight %. 
     
     
         4 . The method of  claim 1  wherein the third layer comprises aluminum at a concentration between 0 and 2 weight %. 
     
     
         5 . The method of  claim 1  wherein the third layer comprises zinc at a concentration between 10 and 45 weight %. 
     
     
         6 . The method of  claim 1  wherein the third layer comprises indium at a concentration between 50 and 90 weight %, tin at a concentration between 2 and 8 weight %, aluminum at a concentration between 0 and 2 weight %, and zinc at a concentration between 10 and 45 weight %. 
     
     
         7 . The method of  claim 1  further comprising:
 forming a fourth layer above a second surface of the substrate, wherein the fourth layer comprises a n-doped amorphous silicon layer; 
 forming a fifth layer above the fourth layer, wherein the fifth layer comprises a resistive metal oxide layer and wherein the fifth layer forms an ohmic contact to the fourth layer; and 
 forming a sixth layer above the fifth layer, wherein the sixth layer comprises a transparent conductive oxide layer, wherein the third layer comprises indium-tin-aluminum-zinc-oxide. 
 
     
     
         8 . The method of  claim 7  wherein the sixth layer comprises indium at a concentration between 50 and 90 weight %. 
     
     
         9 . The method of  claim 7  wherein the sixth layer comprises tin at a concentration between 2 and 8 weight %. 
     
     
         10 . The method of  claim 7  wherein the sixth layer comprises aluminum at a concentration between 0 and 2 weight %. 
     
     
         11 . The method of  claim 7  wherein the sixth layer comprises zinc at a concentration between 10 and 45 weight %. 
     
     
         12 . The method of  claim 7  wherein the sixth layer comprises indium at a concentration between 50 and 90 weight %, tin at a concentration between 2 and 8 weight %, aluminum at a concentration between 0 and 2 weight %, and zinc at a concentration between 10 and 45 weight %. 
     
     
         13 . A heterojunction solar cell comprising:
 a first layer formed above a first surface of a substrate, wherein the first layer comprises a p-doped amorphous silicon layer;   a second layer formed above the first layer, wherein the second layer comprises a metal oxide layer and wherein the second layer forms an ohmic contact to the first layer; and   a third layer formed above the second layer, wherein the third layer comprises a transparent conductive oxide layer, wherein the third layer comprises indium-tin-aluminum-zinc-oxide.   
     
     
         14 . The heterojunction solar cell of  claim 13  wherein the third layer comprises indium at a concentration between 50 and 90 weight %. 
     
     
         15 . The heterojunction solar cell of  claim 13  wherein the third layer comprises tin at a concentration between 2 and 8 weight %. 
     
     
         16 . The heterojunction solar cell of  claim 13  wherein the third layer comprises aluminum at a concentration between 0 and 2 weight %. 
     
     
         17 . The heterojunction solar cell of  claim 13  wherein the third layer comprises zinc at a concentration between 10 and 45 weight %. 
     
     
         18 . The heterojunction solar cell of  claim 13  wherein the third layer comprises indium at a concentration between 50 and 90 weight %, tin at a concentration between 2 and 8 weight %, aluminum at a concentration between 0 and 2 weight %, and zinc at a concentration between 10 and 45 weight %. 
     
     
         19 . The heterojunction solar cell of  claim 13  further comprising:
 forming a fourth layer above a second surface of the substrate, wherein the fourth layer comprises a n-doped amorphous silicon layer; 
 forming a fifth layer above the fourth layer, wherein the fifth layer comprises a metal oxide layer and wherein the fifth layer forms an ohmic contact to the fourth layer; and 
 forming a sixth layer above the fifth layer, wherein the sixth layer comprises a transparent conductive oxide layer, wherein the third layer comprises indium-tin-aluminum-zinc-oxide. 
 
     
     
         20 . The heterojunction solar cell of  claim 19  wherein the sixth layer comprises indium at a concentration between 50 and 90 weight %, tin at a concentration between 2 and 8 weight %, aluminum at a concentration between 0 and 2 weight %, and zinc at a concentration between 10 and 45 weight %.