Influence of post-grown treatments on CuInS2 thin films prepared by sulphurization of Cu-In films

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 CuxS phase segregated on the surface of the as-grown films. To improve the crystalline quality of CuInS2 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 CuxS 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 crystalline quality of the CIS film was significantly improved, which provided a novel method to improve the performance of thin film solar cells.