Polycrystalline CuInS2 (CIS) films were prepared by sulphurization of Cu-In films.The surface morphology and phase composition of the as-grown film,the KCN-etched film,and the annealed KCN-etched film were investigated.During the sulphurization,the secondary CuχS phase segregated on the surface of the as-grown films.To improve the crystalline quality of CulnS2 films,a series of post-grown treatments,such as KCN-etching and vacuum annealing KCN-etched films,were performed on the as-grown films.Both as-grown and post-treated films were characterized by X-ray diffraction (XRD),scanning electron microscopy (SEM),and energy dispersive spectroscopy (EDS).The results indicated that a CuχS secondary phase segregated on the surface of the as-grown film,which could be removed effectively by KCN etching.After the vacuum annealing treatment,the KCN-etched film had a sphalerite structure with (112) preferred orientation.Meanwhile,the crstalline quality of the CIS film was significantly improved,which provided a novel method to improve the performance of thin film solar cells.