Double layered transparent conductive oxide for reduced schottky barrier in photovoltaic devices

Abstract

A device and method for fabricating a photovoltaic device includes forming a double layer transparent conductive oxide on a transparent substrate. The double layer transparent conductive oxide includes forming a doped electrode layer on the substrate, and forming a buffer layer on the doped electrode layer. The buffer layer includes an undoped or p-type doped intrinsic form of a same material as the doped electrode layer. A light-absorbing semiconductor structure includes a p-type semiconductor layer on the buffer layer, an intrinsic layer and an n-type semiconductor layer.

1 . A photovoltaic device, comprising:
 a transparent substrate;   a double layer transparent conductive oxide formed on the substrate, the double layer including:
 a doped electrode layer formed on the substrate; and 
 a buffer layer formed on the doped electrode layer, the buffer layer including an oppositely doped form of a same material as the doped electrode layer; and 
   a light-absorbing semiconductor structure including a p-type semiconductor layer on the buffer layer, an intrinsic layer and an n-type semiconductor layer.   
     
     
         2 . The device as recited in  claim 1 , wherein the buffer layer includes a work function having a value between values of work functions of the doped electrode layer and the p-type semiconductor layer. 
     
     
         3 . The device as recited in  claim 1 , wherein the doped electrode layer and the buffer layer include ZnO. 
     
     
         4 . The device as recited in  claim 1 , wherein the buffer layer includes a thickness between about 100 nm and 500 nm. 
     
     
         5 . The device as recited in  claim 1 , further comprising a second electrode formed on the light-absorbing semiconductor structure. 
     
     
         6 . The device as recited in  claim 1 , wherein the p-type semiconductor layer includes at least one of Si and SiC. 
     
     
         7 . The device as recited in  claim 1 , further comprising a textured surface formed on the double layer to provide a three-dimensional structure. 
     
     
         8 . The device as recited in  claim 1 , wherein the buffer layer includes p-type dopants increasing in concentration from the doped electrode layer. 
     
     
         9 . The device as recited in  claim 1 , wherein the buffer layer includes n-type dopants decreasing in concentration from the doped electrode layer. 
     
     
         10 . The device as recited in  claim 1 , wherein the doped electrode layer includes ZnO with one of B or Al dopants. 
     
     
         11 . The device as recited in  claim 1 , wherein the buffer layer includes p-type dopants increasing in concentration from the doped electrode layer and n-type dopants decreasing in concentration from the doped electrode layer. 
     
     
         12 . A photovoltaic device, comprising:
 a glass substrate;   a double layer transparent conductive oxide formed on the substrate, the double layer including:
 a doped ZnO layer formed on the substrate; and 
 an oppositely doped ZnO buffer layer formed on the doped ZnO layer; and 
   a light-absorbing semiconductor structure including a p-type semiconductor layer on the buffer layer, an intrinsic layer and an n-type semiconductor layer, the buffer layer having a work function value between values of work functions of the doped ZnO layer and the p-type semiconductor layer.   
     
     
         13 . The device as recited in  claim 12 , wherein the buffer layer includes a thickness between about 100 nm and 500 nm. 
     
     
         14 . The device as recited in  claim 12 , further comprising a second electrode formed on the light-absorbing semiconductor structure. 
     
     
         15 . The device as recited in  claim 12 , wherein the p-type semiconductor layer includes at least one of Si and SiC. 
     
     
         16 . The device as recited in  claim 12 , further comprising a textured surface formed on the double layer to provide a three-dimensional structure. 
     
     
         17 . The device as recited in  claim 12 , wherein the buffer layer includes p-type dopants increasing in concentration from the doped electrode layer. 
     
     
         18 . The device as recited in  claim 12 , wherein the buffer layer includes n-type dopants decreasing in concentration from the doped electrode layer. 
     
     
         19 . The device as recited in  claim 12 , wherein the doped ZnO layer includes one of B or Al dopants. 
     
     
         20 . The device as recited in  claim 12 , wherein the buffer layer includes p-type dopants increasing in concentration from the doped electrode layer and n-type dopants decreasing in concentration from the doped electrode layer.