Preparation and Properties of Cu4SnS4 Thin Films

The ternary semiconductor, copper tin sulphide (Cu4SnS4) is considered to be a promising absorber layer in the development of thin film heterojunction solar cells due to its optimum physical properties. Further, it contained more abundant and cheaper elements that are environmentally safe to handle. In the present study, Cu4SnS4 (CTS) films were deposited by co-evaporation technique at various deposition temperatures in the range 200 – 350℃. The effect of substrate temperature (Ts) on the growth of CTS films was investigated. The structure, composition, morphology and optical properties of the films were studied using appropriate techniques. The X-ray diffraction analyses revealed that all the deposited films were polycrystalline and showed the (221) plane as the preferred orientation. The energy dispersive spectroscopy analysis indicated all the three elements, Cu, Sn and S. The grain size of the films was varied in the range 180 – 350 nm. The average optical transmittance of the films was found to be ~ 80% in the visible region and the evaluated optical band gap of the films increased from 1.70 eV to 1.93 eV with the increase of substrate temperature.