Chalcogenide-based materials and methods of making such materials under vacuum using post-chalcogenization techniques

Abstract

The present invention provides strategies for making high quality CIGS photoabsorbing compositions from sputtered precursor film(s). The precursors are converted into CIGS photoabsorbing material via a chalcogenizing treatment (also referred to as “post-chalcogenization,” including, e.g., “post-selenization” when Se is used and/or “post-sulfurization” when S is used) using techniques that allow the post-chalcogenizing treatment to occur under atypically low pressure conditions. Consequently, the strategies of the invention are readily incorporated into batch processes or continuous processes such as roll-to-roll process occurring under vacuum. The present invention is useful at lab, pilot plant, and industrial scales.

1 . A method of making a chalcogen-containing photoabsorbing composition, comprising the steps of:
 a) forming a workpiece comprising a precursor of the chalcogen-containing photoabsorber;   b) forming a cap on the precursor, said cap comprising at least one chalcogen;   c) heating the capped workpiece to cause chalcogenization at a pressure of below about 300 millitorr.   
     
     
         2 . The method of  claim 1 , wherein the process occurs in a roll-to-roll manufacturing process. 
     
     
         3 . The method of  claim 1 , wherein the heating occurs in the presence of an inert gas. 
     
     
         4 . The method of  claim 1 , wherein the cap incorporates at least one chalcogen in elemental form. 
     
     
         5 . The method of  claim 4 , wherein the cap comprises elemental Se. 
     
     
         6 . The method of  claim 1 , wherein at least the heating step occurs in the presence of at least one gas comprising a chalcogen. 
     
     
         7 . The method of  claim 6 , wherein at least the annealing step occurs in the presence of a gas comprising H 2 S or H 2 Se. 
     
     
         8 . The method of  claim 1 , wherein the chalcogenization treatment converts at least a portion of the precursor to a chalcogenide photoabsorbing material. 
     
     
         9 . The method of  claim 1 , wherein the heating temperature is in the range from about 300° C. to about 600° C. 
     
     
         10 . The method of  claim 1 , wherein at least the heating step occurs at a pressure of less than about 100 millitorr. 
     
     
         11 . The method of  claim 1 , wherein at least the heating step occurs at a pressure less than about 50 millitorr. 
     
     
         12 . The method of  claim 1 , wherein the precursor film comprises Cu, In, and Ga. 
     
     
         13 . The method of  claim 12 , wherein the step of forming the workpiece comprises using a sputtering target comprising Cu, In and Ga to form the precursor. 
     
     
         14 . The method of  claim 12 , wherein the step of forming the workpiece comprises using at least one confocal target to form the precursor. 
     
     
         15 . The method of  claim 1 , wherein the precursor comprises a sub-stoichiometric amount of at least one chalcogen. 
     
     
         16 . The method of  claim 1 , wherein the heating occurs at a rate in the range from about 5° C./minute to about 400° C./minute. 
     
     
         17 . The method of  claim 16 , wherein the heating occurs at a rate having a substantially linear profile. 
     
     
         18 . The method of  claim 1 , wherein the workpiece is maintained at one or more temperatures below about 100° C. prior to the heating step. 
     
     
         19 . The method of  claim 1 , wherein the step of forming the workpiece comprises (a) cleaning a metallic support under conditions effective to remove organic impurities and (b) forming the workpiece on a substrate incorporating the cleaned metallic support.