Structural, SEM and Nucleation Characterization of Electrochemically Synthesized CuInSe2 Thin Films

Near-stoichiometric CuInSe2 thin films were synthesized by one-step electrodeposition on molybdenum-coated glass substrates. Cyclic voltammetry measurements were firstly used to investigate the electrodeposition mechanisms. The electrochemical, structural, composition and nucleation properties of these films were investigated by cyclic voltammetry, scanning electron microscopy (SEM) and x-ray diffraction (XRD) using an energy dispersive x-ray spectrometer. Analysis of the nucleation mechanisms indicated that the electrodeposition of CuInSe2 from a single bath solution involved an instantaneous 3-D nucleation. An appropriate deposition-imposed potential range of −700 to −400 mV/SCE was determined, although the reduction peak of indium occurred around −960 mV/SCE. The most suitable deposition potential for film preparation was determined to be −500 mV/SCE. The XRD results showed that the films exhibit a polycrystalline tetragonal CuInSe2 phase with (112) orientation. The composition of the film deposited at −500 mV/SCE is very close to the stoichiometric ratio of 1:1:2 according to energy-dispersive x-ray spectroscopy measurements. We discuss the results obtained for the SEM and structural properties of the latter films, which were subjected to a post-annealing process under vacuum at temperatures of 300, 400 and 500°C for 30 min.