Photovoltaic Devices Including An Interfacial Layer
A photovoltaic cell can include an interfacial layer in contact with a semiconductor 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; 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 device of claim 1 wherein the second semiconductor layer includes a CdTe.
3 . The device of claim 1 wherein the second semiconductor layer includes an alloy of CdTe.
4 . The device of claim 2 wherein the second semiconductor layer includes CdTe alloys wherein Cd is at least partially replaced by Zn, Hg, Mg or Mn.
5 . The device of claim 2 wherein the second semiconductor layer includes CdTe alloys wherein Te is at least partially replaced by S, Se or O.
6 . The device of claim 2 wherein the chemical potential is that of Cd.
7 . The device of claim 1 wherein the chemical potential is controlled within a region of the semiconductor proximate to the interface of the second semiconductor.
8 . The device of claim 1 wherein the interfacial layer is between the second semiconductor layer and a back electrode.
9 . The device of claim 1 wherein the interfacial layer is a third semiconductor layer.
10 . The device of claim 1 wherein the semiconductor material includes ZnTe, CdZnTe, CuAlS 2 , CuAlSe 2 , CuAlO 2 , CuGaO 2 , or CuInO 2 .
11 . The device of claim 1 wherein the interfacial material includes GeTe, CdTe:P, CdTe:N, NiAs or NbP.
12 . The device of claim 2 wherein the surface includes chemical bonds between Cd and an element from column VA of the periodic table.
13 . The device of claim 12 wherein the surface includes chemical bonds between Cd and N, P, As, and Sb.
14 . The device of claim 1 wherein the interfacial layer is between the second semiconductor and the first semiconductor layer.
15 . The 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.
16 . The device of claim 1 wherein the interfacial layer is a compound of Cd with one any of the chalcogenides including O, S, or Se.
17 . The device of claim 1 wherein the interfacial layer includes a CdS.
18 . The device of claim 2 wherein the surface includes chemical bonds between Te and any of the elements from column IIIA of the periodic table.
19 . The device of claim 18 wherein the surface includes chemical bonds between Te and B, Al, Ga, In, or Tl.
20 . The 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.
21 . The device of claim 1 wherein second semiconductor layer is less than 2 um thick.
22 . The device of claim 1 wherein the second semiconductor layer is less than 1 um thick.
23 . The device of claim 1 further comprising an additional interfacial layer between a transparent conductive layer and a first semiconductor layer.
24 . A method of manufacturing a photovoltaic device comprising:
depositing a first semiconductor layer on a substrate, the first semiconductor layer including a wide bandgap semiconductor;
depositing a second semiconductor layer over the first semiconductor layer; and
depositing an interfacial layer to contact a second semiconductor layer, wherein the interfacial layer maintains the chemical potential of the second semiconductor layer at a controlled level.
25 . The method of claim 24 , wherein the interfacial layer is deposited by sputtering.
26 . The method of claim 24 , wherein the interfacial layer is deposited by atomic layer deposition.
27 . The method of claim 24 , wherein the interfacial layer is deposited by selective ion layer adsorption and reaction deposition.
29 . A system for generating electrical energy comprising:
a transparent conductive layer on a substrate;
a first semiconductor layer including a wide bandgap semiconductor;
a second semiconductor layer;
an interfacial layer in contact with a second semiconductor layer, wherein the interfacial layer maintains the chemical potential of the second semiconductor layer at a controlled level;
a first electrical connection connected to the transparent conductive layer; and
a second electrical connection connected to the back metal contact.
30 . The system of claim 29 wherein the transparent conducting layer electrode is replaced by a metallic electrode, and the metallic back electrode is replaced by a transparent conducting layer electrode.
31 . The system of claim 29 further comprising a first electrode connected to the transparent conductive layer and a second electrode connected to the back metal contact.
32 . The system of claim 29 wherein the back metal electrode is replaced by a transparent conductive layer and the device is used in tandem with another photovoltaic device.