Chalcogenide-based materials and improved methods of making such materials

Abstract

The present invention provides strategies for making high quality CIGS photoabsorbing materials from precursor films that incorporate a sub-stoichiometric amount of chalcogen(s). Chalcogen(s) are incorporated into the CIGS precursor film via co-sputtering with one or more other constituents of the precursor. Optional annealing also may be practiced to convert precursor into more desirable chalcopyrite crystalline form in event all or a portion of the precursor has another constitution. The resultant precursors generally are sub-stoichiometric with respect to chalcogen and have very poor electronic characteristics. The conversion of these precursors into CMS photoabsorbing material via chalcogenizing treatment occurs with dramatically reduced interfacial void content. The resultant CIGS material displays excellent adhesion to other layers in the resultant photovoltaic devices. Ga migration also is dramatically reduced, and the resultant films have optimized Ga profiles in the top or bottom portion of the film that improve the quality of photovoltaic devices made using the films.