Electron small polarons and their transport in bismuth vanadate: A first principles study

Relatively low electron mobility has been thought to be a key factor that limits the overall photocatalytic performance of BiVO₄, but the behavior of electrons has not been fully elucidated. We examine electron localization and transport in BiVO₄ using hybrid density functional theory calculations. An excess electron is found to remain largely localized on one V atom. The predicted hopping barrier for the small polaron is 0.35 eV (with inclusion of 15% Hartree-Fock exchange), and tends to increase almost linearly with lattice constant associated with pressure and/or temperature changes. We also examine the interaction between polarons, and discuss the possible concentration-dependence of electron mobility in BiVO₄.