Thin film solar cell and method of forming same

Abstract

A solar cell device with improved performance and a method of fabricating the same is described. The solar cell includes a back contact layer formed on a substrate, an absorber layer formed on the back contact layer, a buffer layer formed on the absorber layer, and a front contact layer formed by depositing a transparent conductive oxide layer on the buffer layer and annealing the deposited TCO layer.

What is claimed is: 
     
         1 . A solar cell comprising
 a back contact layer;   an absorber layer on the back contact layer;   a buffer layer on the absorber layer; and   a front contact layer above the buffer layer, said front contact layer comprising an annealed TCO layer.   
     
     
         2 . The solar cell as in  claim 1 , wherein said annealed TCO layer comprises a material selected from the group consisting of zinc oxide, indium oxide, indium tin oxide, and cadmium oxide. 
     
     
         3 . The solar cell as in  claim 1 , wherein said annealed TCO layer comprises a metal oxide material comprising dopants selected from the group consisting of aluminum, boron, tin, and indium. 
     
     
         4 . The solar cell as in  claim 1 , wherein said annealed TCO layer has a transmittance of at least 80% at wavelengths from about 400 to about 1200 nm. 
     
     
         5 . The solar cell as in  claim 4 , wherein said annealed TCO layer has a sheet resistance of less than 15 ohms per square. 
     
     
         6 . A solar cell, comprising:
 a substrate;   a back contact layer directly physically contacting the substrate, wherein the back contact layer comprises a metal;   an absorber layer directly physically contacting the back contact layer;   a buffer layer directly physically contacting the absorber layer;   an annealed transparent conductive oxide (TCO) layer directly physically contacting the buffer layer;   a first scribe line formed through the back contact layer, wherein the first scribe line is filled with material of the absorber layer and directly contacts the substrate;   a second scribe line formed through the buffer layer and the absorber layer, wherein the second scribe line is filled with material of the annealed TCO layer; and   a third scribe line formed through the annealed TCO layer, the buffer layer, and the absorber layer after the annealing that exposes the back contact layer at an end of the third scribe line.   
     
     
         7 . The solar cell of  claim 6 , wherein said annealed TCO layer comprises a doped metal oxide. 
     
     
         8 . The solar cell of  claim 6 , wherein said annealed TCO layer comprises a material selected from the group consisting of zinc oxide, indium oxide, indium tin oxide, and cadmium oxide. 
     
     
         9 . The solar cell of  claim 6 , wherein said annealed TCO layer comprises a metal oxide material comprising dopants selected from the group consisting of aluminum, boron, tin, and indium. 
     
     
         10 . The solar cell of  claim 6 , wherein said annealed TCO layer has a transmittance of at least 80% at wavelengths from about 400 to about 1200 nm. 
     
     
         11 . The solar cell of  claim 6 , wherein said annealed TCO layer has a sheet resistance of less than 15 ohms per square. 
     
     
         12 . The solar cell of  claim 11 , wherein said annealed TCO layer has a transmittance of at least 80% at wavelengths from about 400 to about 1200 nm. 
     
     
         13 . A solar cell, comprising:
 a substrate;   a back contact layer directly physically contacting the substrate, wherein the back contact layer comprises a metal;   an absorber layer directly physically contacting the back contact layer;   a buffer layer directly physically contacting the absorber layer; and   an annealed transparent conductive oxide (TCO) layer to directly physically contact the buffer layer; and   at least one scribe line form through at least one of: (1) the back contact layer, (2) the buffer layer and the absorber layer, and (3) the annealed TCO layer, the buffer layer, and the absorber layer.   
     
     
         14 . The solar cell of  claim 13 , wherein the at least one scribe line comprises a scribe line formed through the back contact layer, wherein the scribe line is filled with material of the absorber layer and directly contacts the substrate 
     
     
         15 . The solar cell of  claim 13 , wherein the at least one scribe line comprises a scribe line formed through the buffer layer and the absorber layer, wherein the scribe line is filled with material of the annealed TCO layer. 
     
     
         16 . The solar cell of  claim 13 , wherein the at least one scribe line comprises a scribe line formed through the annealed TCO layer, the buffer layer, and the absorber layer after the annealing that exposes the back contact layer at an end of the scribe line. 
     
     
         17 . The solar cell of  claim 13 , wherein the at least one scribe line comprises:
 a first scribe line formed through the back contact layer, wherein the first scribe line is filled with material of the absorber layer and directly contacts the substrate;   a second scribe line formed through the buffer layer and the absorber layer, wherein the second scribe line is filled with material of the annealed TCO layer; and   a third scribe line formed through the annealed TCO layer, the buffer layer, and the absorber layer after the annealing that exposes the back contact layer at an end of the third scribe line.   
     
     
         18 . The solar cell of  claim 13 , wherein said annealed TCO layer comprises a doped metal oxide. 
     
     
         19 . The solar cell of  claim 13 , wherein said annealed TCO layer comprises a material selected from the group consisting of zinc oxide, indium oxide, indium tin oxide, and cadmium oxide. 
     
     
         20 . The solar cell of  claim 13 , wherein said annealed TCO layer comprises a metal oxide material comprising dopants selected from the group consisting of aluminum, boron, tin, and indium.