Hubbard�s Modified Density Functional Theory Calculations for the Electronic Structure and Optical Properties of Carbon Doped Anatase TiO2

Reducing the bandgap of TiO2 to an optimal range by doping with other atoms is a very effective method having great potential in solar energy applications. The fundamental effect of structural changes upon the electronic structure of doped semiconducting TiO2 is very much important to explore an effective doping configuration. A detailed computational study is therefore, required, to better understand the effect of different doped materials upon the structural, electronic and optical properties. We systematically study the carbon doped anatase TiO2, using first-principle density functional theory (DFT) calculations to determine the effect of carbon concentration on the structural, electronic and optical properties of C doped TiO2. We optimize the geometric structures of carbon doped anatase TiO2 using generalized gradient approximation (GGA) with Perdew�Burke�Ernzerhof (PBE) potential (GGA+PBE). Furthermore, to study optical and electronic properties, we perform the calculation with GGA+Hubbard potential (GGA+U) exchange correlational functional. The results confirm that GGA+PBE produce more accurate results for the geometric structure of undoped and carbon doped TiO2, closer to the experimental results. Moreover, GGA+U functional presents the bandgap energies of doped and undoped systems that are close to the actual values at lower computational cost. As a result of carbon doping, new impurity levels have been introduced into the bandgap region of TiO2 that leads to the decrease of bandgap energy. Narrowing the bandgap resulting in shift of the optical absorption edge to the visible region that might enhance the photocatalytic activity. © 2021, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.