Nanostructured TiO2 and S and Fe co-doped TiO2 thin films with high
transparency were prepared on glass substrate through ultrasonic-assisted
spray pyrolysis technique. The effects of doping on morphological, optical
and structural properties of TiO2 were studied by scanning electron
microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray
diffraction (XRD), photoluminescence spectroscopy, Raman spectroscopy,
and UV-visible absorption spectroscopy techniques. Because of the high
uniformity and monodispersity of the prepared thin films, they have high
visible light transparency. All of the prepared thin films have anatase crystal
structure, however, introduction of the dopants, especially S dopant, in the
lattice of TiO2 creates some structural defects in the TiO2. Because of the
presence of defects as charge trapping center in the structure of the doped
TiO2 samples, these thin films have lower electron–hole recombination
rate than undoped TiO2. Furthermore, simultaneous doping of S and Fe
considerably narrows the band gap energy of TiO2.