Effect of different copper precursor layer thickness on properties of Cu2ZnSnS4 (CZTS) thin films prepared by sulfurization of thermally deposited stacked metallic layers

Abstract

Cu2ZnSnS4 (CZTS) thin films were fabricated by sulfurization of thermally evaporated metallic precursors on glass substrates. While the Zinc and Tin thicknesses were kept constant at 300 and 200nm respectively, three Copper layer thicknesses of 100, 150 and 200 nm were used to obtain the metallic precursors. The precursor films were sulfurized for 3 hours at 550 0C with an initial ramping rate of 10 0C/min. X-ray diffraction studies reveal polycrystalline films exhibiting Kesterite structures with preferential orientation along [112] direction. The films with lowest Cu layer thickness exhibited binary metal alloy contents, which disappears with higher Cu precursor layer thickness. The surface morphology and elemental composition of CZTS thin films was determined from scanning electron microscopy and energy dispersive spectroscopy analysis respectively. The grain size become large with increasing Cu/(Zn + Sn) ratio, exhibiting an enhancement of the grain growth under Cu – rich condition. There is a nominal increase in the optical band gap from 1.49 to 1.51 eV with increase in Cu content. The samples resistivities are in the range of 0.8 to 1.5Ωcm