Photovoltaic Devices Including an Interfacial Layer

Abstract

A photovoltaic cell can include an interfacial layer in contact with a semiconductor layer.

What is claimed is: 
     
         1 . A photovoltaic device comprising:
 a transparent conductive layer on a substrate;   a first semiconductor layer including a wide bandgap semiconductor;   a second semiconductor layer having a surface, wherein the second semiconductor layer includes a CdTe alloy wherein Te is at least partially replaced by Se; and   an interfacial layer in contact with the second semiconductor layer;   wherein the interfacial layer maintains a chemical potential of the second semiconductor layer at a controlled level.   
     
     
         2 . The photovoltaic device of  claim 1 , wherein the second semiconductor layer includes a CdTe alloy wherein Cd is at least partially replaced by Zn, Hg, Mg, or Mn. 
     
     
         3 . The photovoltaic device of  claim 1 , wherein the chemical potential is that of Cd. 
     
     
         4 . The photovoltaic device of  claim 1 , wherein the chemical potential is controlled within a region of the second semiconductor layer proximate to an interface of the second semiconductor layer. 
     
     
         5 . The photovoltaic device of  claim 1 , wherein the interfacial layer is a third semiconductor layer. 
     
     
         6 . The photovoltaic device of  claim 1 , wherein the interfacial layer includes ZnTe, CdZnTe, CuAlS 2 , CuAlSe 2 , CuAlO 2 , CuGaO 2 , or CuInO 2 . 
     
     
         7 . The photovoltaic device of  claim 1 , wherein the interfacial layer includes GeTe, CdTe:P, CdTe:N, NiAs, or NbP. 
     
     
         8 . The photovoltaic device of  claim 1 , wherein the surface includes chemical bonds between Cd and an element from column VA of the periodic table. 
     
     
         9 . The photovoltaic device of  claim 8 , wherein the surface includes chemical bonds between Cd and N, P, As, and Sb. 
     
     
         10 . The photovoltaic device of  claim 1 , wherein the interfacial layer is between the second semiconductor layer and the first semiconductor layer. 
     
     
         11 . The photovoltaic device of  claim 1  in which the first semiconductor layer is SnO 2 , SnO 2 :Zn, SnO 2 :Cd, ZnO, ZnSe, GaN, In 2 O 3 , CdSnO 3 , ZnS, or CdZnS. 
     
     
         12 . The photovoltaic device of  claim 1  wherein the interfacial layer is a compound of Cd with any one of the chalcogenides. 
     
     
         13 . The photovoltaic device of  claim 1 , wherein the surface includes chemical bonds between Te and any of the elements from column IIIA of the periodic table. 
     
     
         14 . The photovoltaic device of  claim 1 , wherein the surface includes chemical bonds between Te and B, Al, Ga, In, or Tl. 
     
     
         15 . The photovoltaic device of  claim 1 , wherein the interfacial layer is a material with a chemical formula ABO 2 , wherein A is either Cu, Ag, Au, Pt, or Pd, and B is one of the trivalent metal ions Al, In, Cr, Co, Fe, Ga, Ti, Co, Ni, Cs, Rh, Sn, Y, La, Pr, Nd, Sm, or Eu, or doped compositions thereof. 
     
     
         16 . The photovoltaic device of  claim 1  wherein the second semiconductor layer is less than 2 μm thick. 
     
     
         17 . The photovoltaic device of  claim 1  further comprising an additional interfacial layer between the transparent conductive layer and the first semiconductor layer. 
     
     
         18 . The photovoltaic device of  claim 1 , wherein the interfacial layer includes an oxide or doped compositions thereof. 
     
     
         19 . The photovoltaic device of  claim 1 , wherein the wide bandgap semiconductor is n-type, has a bandgap greater than 2.4 eV, and has a conduction band minima with a positive offset compared to a conduction band minima of the second semiconductor layer. 
     
     
         20 . A photovoltaic device comprising:
 a transparent conductive layer on a substrate;   a first semiconductor layer including a wide bandgap semiconductor;   a second semiconductor layer having a surface, wherein the second semiconductor layer includes a CdTe alloy wherein Cd is at least partially replaced by Zn, Hg, Mg, or Mn; and   an interfacial layer in contact with the second semiconductor layer;   wherein the interfacial layer maintains a chemical potential of the second semiconductor layer at a controlled level.