Preparation of CuInS2 thin films by paste coating

Precursor pastes were obtained by milling In2S3 and CuS. CuInS2 thin films were successfully prepared by precursor layers, which were coated on glasses and Mo foils substrates using these pastes, and were annealed in a N2 atmosphere. The annealed films were characterized by XRD, scanning electron microscopy (SEM) and UV–vis spectrophotometry. The results indicate that chalcopyrite CuInS2 is formed at 200°C and the crystallinity of this phase is improved as the temperature rises. The compression of precursor layers before annealing step is one of the most essential factors for the preparation of perfect CuInS2 thin films. The UV–vis spectroscopy shows that the observed band gaps of the CuInS2 films increase from 1.21 to 1.45eV corresponding to the Cu/In ratios.