Chalcopyrite Cu(In,Ga)Se2 and Defect Chalcopyrite Cu(In,Ga)3Se5 Materials in Photovoltaic P-N Junctions

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 to the defect chalcopyrite materials withincreased 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 ia increased beyond 30% relative to In.