Reactive sputtered copper indium diselenide films for photovoltaic applications

Single phase chalcopyrite CuInSe2 coatings have been deposited by reactive cosputtering from Cu and In planar magnetron sources operated in an Ar+H2Se working gas. Effective sputtering yields from the conditioned Cu and In targets were approximately 0.7 and 0.5 atoms/unit charge, respectively. Sputtering rate, H2Se injection rate, and H2Se and H2 partial pressure measurements were consistent with the overall reaction Cu+In+2H2Se→CuInSe2+2H2. The formation of near-stoichiometric coatings appears to be aided at elevated temperatures by a reemission mechanism which removes excess In. Photovoltaic devices formed by evaporating CdS onto the sputtered CuInSe2 yielded short circuit currents of about 33 mA/cm2 and efficiencies of about 4%.