Electronic and structural properties of B-, Ge-, Mo-, and W-doped anatase TiO₂

Abstract

There is intensive research by the community to improve materials for renewable energy applications such as hydrogen production, photovoltaics and light-emitting diodes. Titanium dioxide (TiO 2 ) is an important material where we can improve its fundamental properties, through doping aiming to form more efficient devices. Here, we use electronic structure calculations based on density function theory (DFT) to explore the effect of dopants, such as boron (B), germanium (Ge), molybdenum (Mo), and tungsten (W), on the structural and electronic properties of TiO 2 . We investigated both the interstitial and the oxygen substitutional positions, and for the minimized energy optimized structures, we used hybrid DFT calculations to predict the electronic properties through the density of states, which proved costly but not as much to outweigh their advantage in accuracy. For most cases considered, the dopants reduce the theoretical bandgap of TiO 2 , while gap states form. The variation of the bandgap ranges from a very small increase of 0.04[Formula: see text]eV to a significant decrease of 0.8[Formula: see text]eV, while the exact “position” of new gap states differs for each type of dopant and for its “spot” in the crystalline structure. It is proposed that these states and the change of the bandgap contribute to the significant changes in the optical and electronic properties of TiO 2 and can be beneficial to the photovoltaic and photocatalytic applications of TiO 2 and its implementation for hydrogen production.