Quality CuInSe2 and Cu(In,Ga)Se2 thin films processed by single-step electrochemical deposition techniques

Ternary CuInSe2 and quaternary Cu(In,Ga)Se2 chalcopyrite semiconductor films with potential applications as solar absorbers were deposited by single-step electrochemical deposition (ECD) on molybdenum coated glass substrates. The films have been structurally characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM) combined with energy dispersive x-ray analysis (EDAX), x-ray photoelectron spectroscopy (XPS), and Raman spectroscopy. Chalcopyrite phase formation was confirmed already in as-deposited films. The crystal structure of the films was further improved by thermal treatment. Element interdiffusion at the chalcopyrite/Mo/glass interface has been prevented by retaining moderate temperatures of deposition (70 °C) and subsequent annealing (300 °C). The SEM/EDAX analysis revealed the presence of CuxSe secondary phases on the surface of ternary films and almost stoichiometric growth of quaternary deposited on top of ternary films. The XRD and Raman analysis confirmed the high quality assessment of the films being almost equal to that of chalcopyrite selenide layers grown by physical vapor deposition at high temperatures (550–750 °C). The surface sensitive XPS analysis confirmed the absence of other impurities in the ECD processed films except from oxygen and carbon adsorbents by sample exposure to atmospheric air.