Effect of Na Doping on Some Physical Properties of Chemically Sprayed CZTS Thin Films

Abstract

In this work, sodium-doped copper zinc tin sulfide (CZTS) thin films are prepared by depositing them on glass substrates at temperature of (400±10) °C and thickness of (350±10) nm using Chemical Spray Pyrolysis (CSP) technique. 0.02 M of copper chloride dihydrate (CuCl2.2H2O), 0.01 M of zinc chloride (ZnCl2), 0.01 M of tin chloride dihydrate (SnCl2.2H2O), and 0.16 M of thiourea (SC(NH2)2) were used as sources of copper, zinc, tin, and sulphur ions respectively. Sodium chloride (NaCl) at different volumetric ratios of (1, 3, 5, 7 and 9) % was used as a dopant source. The solution is sprayed on glass substrates. XRD diffraction, Raman spectroscopy, FESEM, UV-Vis-NIR, and Hall effect techniques were used to investigate the structural, optical, and electrical properties of the produced films. The XRD diffraction results revealed that all films are polycrystalline, with a tetragonal structure and a preferential orientation along the (112) plane. The crystallite size of all films was estimated using Scherrer's method, and it was found that the crystallite size decreases as the doping ratio increases. The FESEM results revealed the existence of cauliflower-shaped nanoparticles. The optical energy band gap was demonstrated to have a value ranging from 1.6 to 1.51 eV with a high absorption coefficient (α ≥104 cm-1) in the visible region of the spectrum. Hall measurements showed that the conductivity of CZTS thin films with various Na doping ratios have p-type electrical conductivity, and it increases as the Na doping ratio increases.