Effect of Temperature on Structural and Optical Properties of Chemically Deposited Tin Sulfide Thin Films Suitable for Photovoltaic Structures

Abstract

SnS (tin sulphide) is of interest for use as an absorber layer and the wider energy band gap phases e.g. SnS2, Sn2S3and Sn/S/O alloys of interest as Cd-free buffer layers for use in thin film solar cells. Thin films of tin sulphide have been deposited using CBD at three different bath temperatures (27, 35 and 45 °C) onto microscope glass substrates. The X ray diffraction (XRD) analysis of the deposited films reveled that all films has orthorhombic SnS phase as dominant one with preferred orientations along (111) direction. The temperature influence on the crystalline nature and the presence of other phases of SnS has been observed. The average grain size in the films determined from Scherers formula as well as from Williamson-Hall-plot method agrees well with each other. Energy dispersive X-ray (EDAX) analysis used to determine the film composition suggested that films are almost stoichiometric. The scanning electron microscopy (SEM) reveals that deposited films are pinhole free and consists of uniformly distributed spherical grains. The optical analysis in the 200-1200 nm range suggests that direct allowed transitions are dominant in the absorption process in the films with variation in the band gap (~1.79 to ~2.05 eV) due to variation in deposition temperature.