Effects of dopant states on photoactivity in carbon-doped TiO2

Recently an effective photoresponse in the visible-light region was experimentally observed in carbon-doped TiO2. We contribute a theoretical understanding of this phenomenon. Our ab initio density functional theory investigations show that substitutional carbon dopants incorporated into TiO2 drastically affect the electronic structure of the material, thus improving its photoactivity. The resulting bandgap of 2.35 eV predicted in this work agrees with the available experimental observations for carbon concentration around 5%. We also address the effects of doping concentration on the photoresponse of this material.