Effect of Substrate Temperature on Structure, optical and Electrical Properties of Spray Deposited CZTS Thin films

Cu2ZnSnS4 (CZTS) films were deposited for different substrate temperatures by using simple chemical locally built spray deposition technique. Copper chloride (CuCl2), Zinc chloride (ZnCl2), Tin chloride (SnCl4.5H2O) and thiourea (SC(NH2)(2)) were used as Cu+, Zn+, Sn+ and S- ion sources respectively. A set of five CZTS films was deposited using five different substrate temperatures (175, 200, 250, 275, and 300 degrees C). The structure, Morphology, Elemental analysis and Optical properties were studied using X-ray diffratometer (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Analysis (EDX) and UV-Visible Systronic Double Beam (2201) Spectrophotometer, techniques respectively. The XRD spectra showed that all films are polycrystalline and exhibit kesterite tetragonal crystal structure with preferential orientation along (112) direction. The calculated crystallite size was increased with increase in substrate temperature. The surface morphology of CZTS films was improved with increase in substrate temperature. The film sample deposited for 275 degrees C represent excellent spherical granules CZTS crystals of increasing size from 640 nm to 1.8 mu m arranged in regular fashion with some void spaces. The purity of the composition was investigated using Elemental analysis of the deposited films. The optical band gap was estimated using Tauc plots. The band gap obtained was to be in the range of 1.4 to 1.6 eV. The calculated energy band gap (Eg) by using Tauc's plot was about 1.62 eV. The dc electrical resistivity estimated by using IV characteristics of the CZTS film was to be in the range. 5622x10(-2) to 9.746x10(-2) Omega - cm.