Effect of CuO on the photoluminescence quenching and photocatalytic activity of ZnO multilayered thin films prepared by sol-gel spin coating technique

Abstract

Sol-gel spin coating technique has been successfully employed for the preparation of monolayer, bilayer, and multilayer zinc oxide thin films on the glass substrate. The effect of copper oxide (CuO) on the photoluminescence (PL) quenching and photocatalytic activity of multilayered zinc oxide (ZnO) thin films were investigated. The +2 oxidation state of Zn and Cu in multilayered films was confirmed by x-ray photoelectron spectroscopy (XPS). The origin of green emission in the layered film is due to the presence of CuO and it acts as a trap for electrons generated in the ZnO layer thus preventing electron-hole recombination. The photocatalytic activity of multilayer zinc oxide thin films were evaluated on the basis of degradation of malachite green (MG) dye under UV irradiation. The formation of a p-n junction in multilayered zinc oxide thin films dissociate the excitons and this will cause the photoluminescence quenching and enhancement of degradation rate of malachite green in multilayered zinc oxide thin films. The results reveal that the CuO layer improves the crystalline quality, optical and photocatalytic properties of ZnO multilayered thin films.