Properties of SnS Thin Films Grown by a Two-Step Process

Polycrystalline SnS thin films were grown on soda-lime glass substrates by conversion into the compound of a Sn thin film deposited by evaporation, by annealing it in the presence of elemental sulfur (sulfurization). This is a relatively new material, which exhibits good properties for its use as absorbent layer in solar cells. X-ray diffraction (XRD) measurements indicate that the synthesized samples grow in several phases (SnS, SnS₂ and Sn²S₃ ) depending upon the deposition conditions. However, through an exhaustive parameter study, conditions were found to grow thin films predominantly in the SnS phase with orthorhombic structure. It was found that this type of compound presents p-type conductivity, high absorption coefficient (greater than 10⁴ cm^-1) and energy band gap Eg of about 1.3 eV, indicating that this compound has good properties to perform as absorbent layer in thin film solar cells. Study of the structural, morphological and optical properties of tin sulphide films, grown in the SnS and SnS₂ phases, was carried out from XRD, atomic force microscope (AFM) and spectral transmittance measurements. Theoretical simulation of the XRD pattern with the help of the powdercell package allowed us identifying the phases with a good degree of confidence