Photovoltaic Devices Including an Interfacial Layer

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.