Characterization of electrodeposited CuInSe2 (CIS) film

CuInSe2 thin film was grown by one-step cathodic electrodeposition on Pt-coated glass using amperometry mode (fixed potential), in a three-electrode potentiostatic system containing the precursor solutions, 10 mM CuSO4, 50 mM InSO4, 30 mM SeO2, and 0.1 M K2SO4 as a supporting electrolyte, at a pH of 1.5 (±0.1) adjusted with 0.1 M H2SO4. The structure, chemical composition, morphology, optical properties, and uniformity of the electrodeposited CuInSe2 film were characterized by X-ray diffraction (XRD), electron probe micro analysis (EPMA), UV–vis–NIR spectrophotometry, field-emission scanning electron microscopy (FE-SEM), and Auger electron spectroscopy (AES), respectively. Several experiments were conducted in which the deposition voltage and post-annealing conditions were varied. As the applied deposition voltage was increased from −0.6 V to −0.7 V versus Ag/AgCl, a CuInSe2 thin film with a chalcopyrite structure came to be predominantly formed, in accordance with the chemical composition, while the formation of the binary compounds (CuO and CuxSe) which influence the degradation of the performance in the application of CIS-based solar cells, rapidly decreased. The optimum conditions consisted of an annealing temperature of about 350 °C for 30 min under nitrogen ambient. At this temperature, a CuInSe2 thin film, in the form of ternary compound, is formed with the required conditions, namely good crystallinity, good stoichiometry, a suitable bandgap, and depth uniformity.