Chalcopyrite Cu(In,Ga)Se 2 and defect-chalcopyrite Cu(In,Ga) 3Se 5 materials in photovoltaic PN junctions

Abstract

Efficient photovoltaic action in polycrystalline solar cells based on CuInGaSe materials is postulated to rely strongly on a chalcopyrite/defect-chalcopyrite interface. Growth and fundamental properties of such materials are discussed to understand better junction formation in such devices. A change in conductivity type (from n to p) has been observed for the defect chalcopyrite materials with increased Ga content. Specifically, we found that the p-n nature of the interface in uniform Ga content absorbers is only possible at low Ga contents (< 30% relative to In). Furthermore, crystallographic data reveal significant differences in lattice size between both chalcopyrite materials as Ga is increased beyond 30% relative to In.