Chemically Passivated Zinc Oxide Photoelectrode for Photoelectrochemical Water Splitting

Abstract

A chemically passivated photoelectrode, having a conductive substrate, a layer of conductive oxide, preferably zinc oxide (ZnO), over the conductive substrate, and an ultrathin layer of a chemically inert semiconductor material coating the conductive oxide layer, is disclosed. The ultrathin layer of chemically inert semiconductor material, which may be less than 5 nm thick, increases the efficiency of water splitting through passivation of surface charge traps and chemical stability in harsh environments, as opposed to being photoactive. A method of manufacture and a solar cell having the photoelectrode are also disclosed.

1 . A photoelectrode comprising a conductive substrate, a layer of conductive oxide over said conductive substrate, and a layer of chemically inert semiconductor material coating said conductive oxide layer, wherein said layer of chemically inert semiconductor material coating has a thickness of less than 5 nm. 
     
     
         2 . The photoelectrode of  claim 1 , wherein the conductive oxide layer is zinc oxide or cuprous oxide. 
     
     
         3 . The photoelectrode of  claim 1 , wherein the conductive oxide layer is zinc oxide. 
     
     
         4 . The photoelectrode of  claim 2 , wherein the conductive oxide layer comprises conductive oxide nanostructures. 
     
     
         5 . The photoelectrode of  claim 4 , wherein the nanostructures are selected from the group consisting of nanowires, nanorods, and nanotips. 
     
     
         6 . The photoelectrode of  claim 4 , wherein the conductive oxide nanostructures comprise oxygen plasma cleaned conductive oxide nanostructures. 
     
     
         7 . The photoelectrode of  claim 6 , wherein the cleaned conductive oxide nanostructures are thermally annealed at a temperature between about 250° C. and about 500° C. in O 2 . 
     
     
         8 . The photoelectrode of  claim 7 , wherein the cleaned conductive oxide nanostructures are thermally annealed at a temperature of about 500° C. in O 2 . 
     
     
         9 . The photoelectrode of  claim 1 , wherein the chemically inert semiconductor material is selected from the group consisting of TiO 2 , HfO 2 , and ZrO 2 . 
     
     
         10 . The photoelectrode of  claim 1 , wherein the chemically inert semiconductor material is TiO 2 . 
     
     
         11 . The photoelectrode of  claim 1 , wherein the thickness of the chemically inert semiconductor material layer is about 0.9 nm to about 5 nm. 
     
     
         12 . The photoelectrode of  claim 11 , wherein the thickness of the chemically inert semiconductor material layer is about 1 nm. 
     
     
         13 . The photoelectrode of  claim 1 , wherein the conductive oxide layer is doped with one or more foreign elements. 
     
     
         14 . The photoelectrode of  claim 13 , wherein the foreign elements are selected from the group consisting of nitrogen, gallium, and indium. 
     
     
         15 . A solar cell comprising a photoelectrode of  claim 1 . 
     
     
         16 . A method of fabricating a photoelectrode, comprising depositing a layer of a conductive oxide material over a conductive substrate;
 growing nanostructures of said conductive oxide material over said layer of said conductive oxide material; and   depositing an ultrathin layer of a chemically inert semiconductor material over said layer of conductive oxide material.   
     
     
         17 . The method of  claim 16 , wherein the layer of conductive oxide material is thermally annealed at a temperature between about 250° C. and about 500° C. in O 2  prior to the deposition of the layer of chemically inert semiconductor material. 
     
     
         18 . The method of  claim 17 , wherein the layer of conductive oxide material is thermally annealed at a temperature of about 500° C. 
     
     
         19 . The method of  claim 17 , wherein the layer of conductive oxide material is treated with oxygen plasma prior to thermal annealing. 
     
     
         20 . The method of  claim 19 , further comprising the step of thermally annealing the layer of conductive oxide material at a temperature between about 250° C. and about 500° C. in O 2  prior to the deposition of the layer of chemically inert semiconductor material.