On the structural and optical properties of SnS films grown by thermal evaporation method

Abstract

Tin sulphide (SnS) has a direct energy band gap of 1.35 eV and it consists of abundant, non-toxic elements. It is therefore of interest for use as an absorber layer material in thin film photovoltaic solar cells. In this work, SnS layers with thicknesses in the range 2-3.6μm, were thermally evaporated onto glass substrates using substrate temperatures in the range 280°C to 360°C, and the way the structural and optical properties of the layers varied with the deposition conditions investigated. X-ray diffraction spectra showed a strong (040) reflection as the most prominent peak for films formed between 320°C to 360°C. The peak intensity ratio, crystallite size and grain size were observed to increase with increasing substrate temperature whilst the strain decreased. All the layers were highly light absorbing with the optical absorption coefficient, α > 104 cm-1. The optical energy band gap was found to be in the range, 1.30-1.34eV, it not changing substantially with substrate temperature. Other optical parameters such as the refractive index and optical conductivity were also evaluated for the layers grown at different substrate temperatures.