The electronic structure and optical absorption of rutile TiO₂ with La and N dopants from first-principles calculation

The electronic and optical properties of both substitutional and interstitial N-doped, La-doped and N-La co-doped rutile TiO₂ have been investigated systematically by the spin-polarized density functional theory calculations. In substitutional La-N co-doped system, an N 2p impurity state appears in the forbidden gap and has improved the visible light absorption performance by reducing the transition energy. Interstitial La-N co-doping induces several impurity states which helps transfer electrons from valance band maximum to conduction band minimum and an obvious lattice distortion which reduces the recombination of electrons and holes. When the dopant concentration increases or the distance between two dopants shortens, the interaction between dopants will be strengthened, which leads to a better visible-light absorption.