First principles study on the electronic structure and optical property of Nd-C codoped anatase TiO2

Abstract

Band structures, density of states, and absorption spectra of pure, Nd doped, C doped, and Nd-C codoped TiO2 are calculated using first-principles based on density functional theory. Calculation results show that Nd 4f state forms empty impurity energy levels below conduction band, and C 2p state together with Nd 2f state forms occupied impurity energy levels with higher density than that of single doped TiO2 above valence band. Consequently, more electrons in occupied energy levels can be excited by visible light to empty Nd 4f states rather than Ti 3d states, resulting in further enhancement of visible light absorption and absorption edge red shift. In addition, the impurity energy levels act as carriers trap centers, thus decreasing the recombination rate of carriers.