Optical Properties of Cobalt Doped TiO2 Thin Films: Study of Degradation under Band Gap Edge of 412 nm Light Illumination

In this study, it has been aimed to investigate the effect of Co doping on the optical properties of TiO2 thin film and the change in optical properties of Co doped TiO2 thin film with the widest optical bandgap during illuminating by light. For this purpose, Pure and cobalt-doped TiO2 thin films have been prepared by sol-gel technique. The optical properties of the thin films have been characterized by ultraviolet-visible (UV-Vis) light spectrometer. The optical bandgap, transmittance, reflectance and refractive index have been determined. The highest optical bandgap has been recorded for the 3% Co doping as 3.01 eV. Additionally, it has been determined that since cobalt exhibits absorption characteristics that differ from TiO2, particularly at longer wavelengths, it leads to a decrease in the effective refractive index for the composites. The results indicated that the cobalt additive significantly enhanced photo-degradation. To analyze this effect, the composite having 3% Co doping has also been illuminated by 412 nm light that corresponds to 3.01 eV between 20 minutes and 1 hour. As a result, a slight increase in the absorbance has been recorded.