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.