Theoretical and experimental studies on the optical properties of La-doped TiO2 with oxygen vacancies

La-doped anatase TiO2 (La-TiO2) powders were prepared by a sol-gel method. La-TiO2 was characterized by Xray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy, ultraviolet-visible spectroscopy and electron paramagnetic resonance spectroscopy. The test results showed that the powders were anatase TiO2 nanocrystals, and La was successfully doped into the TiO2 crystal cells. In the La-TiO2, there were vacancies. The vacancies were mainly oxygen vacancies (VO). La doping reduced the concentration of VO. With an increase in La doping, the bandgap decreased at first and then increased, and the optical absorption band-edge displayed red shifts at first, then blue shifts. In a theoretical calculation of the La-TiO2 by first principles, VO was introduced into a model of the crystal cell. The calculated change trends of the bandgap and the light absorption with increased La doping were consistent with the measured results. Ignoring the vacancies in theoretical calculations will lead to inconsistencies between the theoretical calculated and experimental results.