Investigation on optical properties of spin coated TiO2/Co composite thin films

The optical properties of spin coated Co doped TiO2 composite films have been studied in the present communication based on the suitability of such materials for possible application in solar cell windows. Before deposition, raw materials of the nanoparticles (NPs) were examined by X-ray diffraction technique for the analysis of their crystal structure. Both the NPs were found to be polycrystalline in nature with mean crystallite sizes of ∼17 and ∼70 nm for TiO2 and Co respectively. The composite films were prepared by adding different concentrations of Co nanoparticles (1-4 wt %) in TiO2 nanoparticles solution. Transmission measurements revealed a strong dependency of film transmission with Co doping concentration with maximum transmission ∼85% @ 550 nm for 4% doping. The optical energy band gap evaluated from Tauc’s law for the films has been found to be blue-shifted with doping with a maximum value of 4.04 eV for 4% doping concentration. Overall results suggest that the thin film composite prepared by 4% Co doping in TiO2 can be a promising candidate to improve the performance of solar cell windows in terms of improved transmission from the reported value of ∼50% @ 550 nm for Ni-doped TiO2 thin films.