Influence of Thiourea Concentration on Some Physical Properties of Chemically Sprayed Cu<sub>2</sub>ZnSnS<sub>4</sub> Thin Films

Abstract

In this work Cu2ZnSnS4 (CZTS) films were deposited by using chemical spray pyrolysis (CSP) technique at substrate temperature of (400 ± 10) °C and thickness of about (300 ± 10) nm at different Thiourea Concentrations of (0.14, 0.16, 0.18, 0.20, 0.22 and 0.24) M. Copper chloride (CuCl), zinc chloride (ZnCl2), tin chloride (SnCl4.5H2O) and thiourea (SC(NH2)2) were used as sources of copper ions, zinc ions, tin ions and sulfur ions respectively. The structural, morphological and optical properties of these films have been studied using XRD, AFM, and UV-Visible spectroscopy respectively. The XRD results showed that all films are polycrystalline in nature with tetragonal structure and preferred orientation along (112) plane. The crystallite size (Dav) of all samples was calculated using Scherrer’s equation and it is found that the sample deposited at thiourea concentration of 0.20 M has maximum crystallite size of 31.25 nm, while it was minimum (18.02 nm) for the sample prepared at thiourea concentration of 0.16 M. The AFM results showed smooth and homogenous thin films. The optical energy band gap (Eg) for allowed direct electronic transition was calculated using Tauc’s plot. It is found that the energy band gap (Eg) decreases as the thiourea concentration increases and it was in the range of (2.22 - 1.75) eV. Urbach energy, refractive index, extinction coefficient and dielectric coefficient of all deposited films were estimated and the results were discussed.