Optical, structural, FTIR and photoluminescence characterization of Cu and Al doped CdS thin films by chemical bath deposition method

Pure CdS, Cd_0.96Cu_0.04S and Cd_0.94Cu_0.04Al_0.02S thin films have been synthesized by simple chemical deposition method. Cubic structure noticed in undoped CdS and Cu-doped CdS thin films was changed into mixer of cubic and hexagonal structure for Cd_0.94Cu_0.04Al_0.02S. The change in crystallite size, peak position and lattice parameters were discussed based on thickness, crystal structure and the density of defect states. Microstructure of the synthesized films was investigated by scanning electron microscope and energy dispersive X-ray spectra which confirmed the presence of compositional elements such as Cd, S, Cu and Al. Higher thickness and the enhanced crystallite size were responsible for the higher absorption in Cd_0.96Cu_0.04S than other films. The higher energy gap (2.56 eV) and enhancement of visible light absorption noticed in Cd_0.96Cu_0.04S thin film led them as an effective way to utilize solar energy and enhance its photocatalytic activity under visible light. The accelerated I_G/I_UV ratio noticed in Al, Cu co-doped CdS film was due to the formation of new energy levels related to defect states produced by Al/Cu impurities and mixer of hexagonal and cubic structure