Analysis of Indium Oxidation State on the Electronic Structure and Optical Properties of TiO₂.

Due to the high formation energy of Indium interstitial defect in the TiO₂ lattice, the most probable location for Indium dopant is substitutional sites. Replacing Ti by In atom in the anatase TiO₂ shifted the absorption edge of TiO₂ towards visible regime. Indium doping tuned the band structure of TiO₂ via creating In 5p states. The In 5p states are successfully coupled with the O 2p states reducing the band gap. Increasing In doping level in TiO₂ improved the visible light absorption. Compensating the charge imbalance by oxygen vacancy provided compensated Indium doped TiO₂ model. The creation of oxygen vacancy widened the band gap, blue shifted the absorption edge of TiO₂ and declined the UV light absorption. The 2.08% In in TiO₂ is the optimal Indium doping concentration, providing suitable band structure for the photoelectrochemical applications and stable geometrical configuration among the simulated models. Our results provide a reasonable explanation for the improved photoactivity of Indium doped TiO₂.