Enhancing efficiency in solar cells by adjusting deposition power

Abstract

Methods for forming a photovoltaic device include adjusting a deposition power for depositing a buffer layer including germanium on a transparent electrode. The deposition power is configured to improve device efficiency. A p-type layer is formed on the buffer layer. An intrinsic layer and an n-type layer are formed over the p-type layer.

What is claimed is: 
     
         1 . A method for forming a photovoltaic device, comprising:
 adjusting a deposition power for depositing a buffer layer including germanium on a transparent electrode, the deposition power being configured to improve device efficiency;   forming a p-type layer on the buffer layer; and   forming an intrinsic layer and an n-type layer over the p-type layer.   
     
     
         2 . The method as recited in  claim 1 , wherein depositing the buffer layer includes depositing at least one of a hydrogenated amorphous silicon germanium alloy, a hydrogenated microcrystalline silicon-germanium alloy, a hydrogenated amorphous germanium or a hydrogenated microcrystalline germanium. 
     
     
         3 . The method as recited in  claim 1 , wherein the deposition power is increased to increase fill factor. 
     
     
         4 . The method as recited in  claim 1 , wherein the buffer layer is formed by a GeH 4  plasma enhanced deposition. 
     
     
         5 . The method as recited in  claim 1 , wherein the p-type layer, the intrinsic layer and the n-type layer are formed at a temperature of about 250 degrees Celsius. 
     
     
         6 . The method as recited in  claim 1 , wherein the buffer layer aligns band gap energies between the transparent electrode and the p-type layer. 
     
     
         7 . The method as recited in  claim 1 , further comprising adjusting a deposition power for the p-type layer to improve device efficiency. 
     
     
         8 . The method as recited in  claim 1 , wherein the p-type layer includes a form of silicon. 
     
     
         9 . The method as recited in  claim 8 , wherein the p-type layer includes at least one of amorphous silicon, amorphous silicon carbide, hydrogenated amorphous silicon, or hydrogenated amorphous silicon carbide. 
     
     
         10 . A method for forming a photovoltaic device, comprising:
 forming a transparent electrode on a transparent substrate, the transparent electrode having a first Fermi level;   adjusting a deposition power for depositing a buffer layer including germanium on the transparent electrode, the deposition power being configured to improve device efficiency, the buffer layer having a Fermi level aligned with the first Fermi level;   depositing a p-type layer on the buffer layer, the p-type layer having a conduction band level aligned with a conduction band level of the buffer layer;   forming an intrinsic layer on the p-type layer; and   forming an n-type layer on the intrinsic layer.   
     
     
         11 . The method as recited in  claim 10 , wherein depositing the buffer layer includes depositing at least one of a hydrogenated amorphous silicon germanium alloy, a hydrogenated microcrystalline silicon-germanium alloy, a hydrogenated amorphous germanium or a hydrogenated microcrystalline germanium. 
     
     
         12 . The method as recited in  claim 10 , wherein the deposition power is increased to increase fill factor. 
     
     
         13 . The method as recited in  claim 10 , wherein the buffer layer is formed by a GeH 4  plasma enhanced deposition. 
     
     
         14 . The method as recited in  claim 10 , wherein the p-type layer, the intrinsic layer and the n-type layer are formed at a temperature of about 250 degrees Celsius. 
     
     
         15 . The method as recited in  claim 10 , further comprising adjusting a deposition power for the p-type layer to improve device efficiency. 
     
     
         16 . The method as recited in  claim 10 , wherein the p-type layer includes a form of silicon. 
     
     
         17 . The method as recited in  claim 16 , wherein the p-type layer includes at least one of amorphous silicon, amorphous silicon carbide, hydrogenated amorphous silicon, or hydrogenated amorphous silicon carbide. 
     
     
         18 . A method for forming a photovoltaic device, comprising:
 forming a transparent conductive oxide on a transparent substrate;   adjusting a first deposition power for depositing a buffer layer including germanium on the transparent electrode, the first deposition power being configured to improve device efficiency;   adjusting a second deposition power for depositing a p-type amorphous layer on the buffer layer such that the second deposition power is configured to improve device efficiency;   forming an amorphous silicon intrinsic layer on the p-type layer;   forming an amorphous silicon n-type layer on the intrinsic layer; and   forming a back reflector on the n-type layer.   
     
     
         19 . The method as recited in  claim 18 , wherein depositing the buffer layer includes depositing at least one of a hydrogenated amorphous silicon germanium alloy, a hydrogenated microcrystalline silicon-germanium alloy, a hydrogenated amorphous germanium or a hydrogenated microcrystalline germanium. 
     
     
         20 . The method as recited in  claim 18 , wherein the p-type layer includes at least one of amorphous silicon, amorphous silicon carbide, hydrogenated amorphous silicon, or hydrogenated amorphous silicon carbide. 
     
     
         21 . A method for forming a photovoltaic device, comprising:
 forming a transparent electrode on a transparent substrate, the transparent electrode having a first Fermi level;   depositing a buffer layer including germanium on the transparent electrode, the buffer layer having a Fermi level substantially aligned with the first Fermi level;   adjusting a deposition power for forming a p-type layer on the buffer layer, the deposition power being configured to improve device efficiency, the p-type layer having a conduction band level aligned with a conduction band level of the buffer layer;   forming an intrinsic layer on the p-type layer; and   forming an n-type layer on the intrinsic layer.   
     
     
         22 . The method as recited in  claim 21 , wherein the buffer layer aligns band gap energies between the transparent electrode and the p-type layer.