Method of manufacture of chalcogenide-based photovoltaic cells

Abstract

The invention is a method of forming a cadmium sulfide based buffer on a copper chalcogenide based absorber in making a photovoltaic cell. The buffer is sputtered at relatively high pressures. The resulting cell has good efficiency and according to one embodiment is characterized by a narrow interface between the absorber and buffer layers. The buffer is further characterized according to a second embodiment by a relatively high oxygen content.

What is claimed is: 
     
         1 . A method comprising
 forming a chalcogenide based absorber layer on a substrate   forming a buffer layer comprising cadmium and sulfur on the absorber by sputtering at a working pressure of from 0.08 to 0.12 mbar.   
     
     
         2 . The method of  claim 1  wherein the atmosphere is inert. 
     
     
         3 . The method of  claim 1  wherein sputtering is from a target of cadmium and sulfur or compounds thereof. 
     
     
         4 . The method of  claim 1  wherein an interface having a thickness of less than 10 nm is formed between the absorber layer and the buffer layer wherein the interface is defined on one side by the point at which the atomic fraction of cadmium exceeds 0.05 in energy dispersive x-ray spectroscopy scans of cross section of the cell and defined on a second side by the point at which the atomic fraction of indium and selenium is less than 0.05 in energy dispersive x-ray spectroscopy scans of cross section of the cell. 
     
     
         5 . The method of  claim 4  wherein the interface is further defined on the second side by the atomic fraction of copper being less than 0.10. 
     
     
         6 . The method of  claim 1  wherein the substrate is flexible and bears a backside electrical contact. 
     
     
         7 . The method of  claim 1  further comprising forming a transparent conductive layer over the buffer layer. 
     
     
         8 . The method of  claim 7  further comprising forming a window layer between the transparent conductive layer and the buffer layer. 
     
     
         9 . The method of  claim 7  comprising forming an electrical connection grid on the transparent conductive layer. 
     
     
         10 . The method of  claim 7  comprising providing a barrier layer over the transparent conductive layer. 
     
     
         11 . The method of  claim 9  comprising providing a barrier layer over the transparent conductive layer and the grid. 
     
     
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