Spray chemical vapor deposition of CuInS₂ thin films for application in solar cell devices

Chalcopyrite CuInS₂ is a direct band gap semiconductor (1.5 eV) that has potential applications in photovoltaic thin film and photoelectrochemical devices. We have successfully employed spray chemical vapor deposition using the previously known, single-source, metallorganic precursor, (Ph₃P)₂CuIn(SEt)₄, to deposit CuInS₂ thin films. Stoichiometric, polycrystalline films were deposited onto fused silica over a range of temperatures (300-400 °C). Morphology was observed to vary with temperature: spheroidal features were obtained at lower temperatures and angular features at 400 °C. At even higher temperatures (500 °C), a Cu-deficient phase, CuIn₅S₈, was obtained as a single phase. The CuInS₂ films were determined to have a direct band gap of ca. 1.4 eV.