Photovoltaic Devices Including An Interfacial Layer

Abstract

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.