First-principle study of electronic structures and optical properties of chromium and carbon co-doped anatase TiO2

The band structure, density of states, electron density difference, and optical properties of Cr and C co-doped anatase TiO2 are studied using first principles calculations under the framework of the density functional theory. We mainly discuss three possible Cr–C adjacent co-doped configurations, where one Cr atom and one C atom substitute for one Ti atom and O atom respectively. The band structures show that the sub-bands induced mainly by C-2p state and Cr-3d state narrow the effective band gap down to ~0.86 eV and ~1.19 eV for different doped configurations. Doped Cr and C ion have different degree polarization, which will promote the electrons and holes separating. The calculated optical absorption spectrum exhibits shifts of the absorption edges of the three Cr–C co-doped TiO2 samples towards the visible light region.