Thin-Film Photovoltaic Structures Including Semiconductor Grain and Oxide Layers

Abstract

Photovoltaic structures for the conversion of solar irradiance into electrical free energy. In a particular implementation, a photovoltaic cell includes a granular semiconductor and oxide layer with nanometer-size absorber semiconductor grains surrounded by a matrix of oxide. The semiconductor and oxide layer may be disposed between electron and hole conducting layers. In some implementations, multiple semiconductor and oxide layers can be deposited.

1 . A photovoltaic cell, comprising:
 a photoactive conversion layer comprising:
 either electron-conducting material or hole-conducting material; and 
 a multiplicity of semiconductor grains arranged within a distinct oxide matrix, wherein each of the semiconductor grains is substantially columnar and has a height substantially equal to a thickness of the photoactive conversion layer, and wherein the oxide matrix is dispersed at least at circumferential grain boundaries of the semiconductor grains; and 
   a semiconductor layer, wherein:
 if the photoactive conversion layer comprises electron-conducting material, then the semiconductor layer comprises hole-conducting material; and 
 if the photoactive conversion layer comprises hole-conducting material, then the semiconductor layer comprises electron-conducting material. 
   
     
     
         2 . The photovoltaic cell of  claim 1 , wherein each of the semiconductor grains in the photoactive conversion layer is substantially columnar along an axis perpendicular to the light-incident surface of the photoactive conversion layer. 
     
     
         3 . The photovoltaic cell of  claim 1 , wherein the semiconductor layer further comprises a multiplicity of semiconductor grains arranged within a distinct oxide matrix, wherein each of the semiconductor grains is substantially and has a height substantially equal to that of a thickness of the semiconductor layer, and wherein the oxide matrix is dispersed at least at circumferential grain boundaries of the semiconductor grains. 
     
     
         4 . The photovoltaic cell of  claim 1 , wherein the semiconductor layer is deposited onto the photoactive conversion layer. 
     
     
         5 . The photovoltaic cell of  claim 1 , wherein the photoactive conversion layer is deposited onto the semiconductor layer. 
     
     
         6 . The photovoltaic cell of  claim 3 , wherein the volumes of the semiconductor grains in the photoactive conversion layer are different than the volumes of the semiconductor grains in the semiconductor layer. 
     
     
         7 . The photovoltaic cell of  claim 3 , wherein the material composition of the semiconductor grains in the photoactive conversion layer is different than the material composition of the semiconductor grains in the semiconductor layer. 
     
     
         8 . The photovoltaic cell of  claim 3 , wherein the photoactive conversion layer and the semiconductor layer have different bandgaps. 
     
     
         9 . The photovoltaic cell of  claim 1 , wherein the semiconductor layer comprises a continuous n-type semiconductor layer. 
     
     
         10 . The photovoltaic cell of  claim 1 , wherein the semiconductor layer comprises a continuous p-type semiconductor layer. 
     
     
         11 . The photovoltaic cell of  claim 1 , wherein the semiconductor layer comprises a continuous metallic layer. 
     
     
         12 . The photovoltaic cell of  claim 1 , wherein the semiconductor layer is substantially uniform in thickness. 
     
     
         13 . The photovoltaic cell of  claim 1 , wherein each of the semiconductor grains in the photoactive conversion layer has a base substantially in contact with the semiconductor layer. 
     
     
         14 . The photovoltaic cell of  claim 1 , further comprising:
 an underlying layer comprising either electron-conducting material or hole-conducting material, wherein the photoactive conversion layer is deposited onto the underlying layer.   
     
     
         15 . The photovoltaic cell of  claim 1 , further comprising:
 an overlying layer comprising either electron-conducting material or hole-conducting material, wherein the overlying layer is deposited onto the photoactive conversion layer.   
     
     
         16 . The photovoltaic cell of  claim 1 , further comprising a substrate. 
     
     
         17 . The photovoltaic cell of  claim 16 , wherein the photoactive conversion layer is deposited onto the substrate. 
     
     
         18 . The photovoltaic cell of  claim 16 , wherein the semiconductor layer is deposited onto the substrate. 
     
     
         19 . The photovoltaic cell of  claim 1 , further comprising a conducting layer. 
     
     
         20 . The photovoltaic cell of  claim 19 , wherein each of the semiconductor grains in the photoactive conversion layer has a base substantially in contact with the conducting layer. 
     
     
         21 . The photovoltaic cell of  claim 19 , wherein the conducting layer comprises transparent conducting oxide material. 
     
     
         22 . The photovoltaic cell of  claim 1 , further comprising:
 a metal-and-oxide layer comprising a multiplicity of metallic grains arranged within an oxide matrix, wherein each of the metallic grains is substantially columnar and has a height substantially equal to a thickness of the metal-and-oxide layer, and wherein the oxide matrix is dispersed at least at circumferential grain boundaries of the metallic grains.   
     
     
         23 . The photovoltaic cell of  claim 22 , wherein the metallic grains in the metal-and-oxide layer are substantially in contact with the semiconductor grains in the photoactive conversion layer. 
     
     
         24 . The photovoltaic cell of  claim 1 , wherein there are a plurality of photoactive conversion layers. 
     
     
         25 . The photovoltaic cell of  claim 1 , wherein there are a plurality of semiconductor layers. 
     
     
         26 . The photovoltaic cell of  claim 25 , wherein at least one photoactive conversion layer is disposed between two semiconductor layers. 
     
     
         27 . The photovoltaic cell of  claim 1 , wherein the thickness of the photoactive conversion layer is greater than an average grain diameter of the semiconductor grains in the photoactive conversion layer. 
     
     
         28 . The photovoltaic cell of  claim 1 , wherein each of the semiconductor grains in the photoactive conversion layer has a substantially circular cross-section.