Band edge electronic structure of BiVO ₄: Elucidating the role of the Bi s and V d orbitals

We report the first-principles electronic structure of BiVO ₄, a promising photocatalyst for hydrogen generation. BiVO ₄ is found to be a direct band gap semiconductor, despite having band extrema away from the Brillouin zone center. Coupling between Bi 6s and O 2p forces an upward dispersion of the valence band at the zone boundary; however, a direct gap is maintained via coupling between V 3d, O 2p, and Bi 6p, which lowers the conduction band minimum. These interactions result in symmetric hole and electron masses. Implications for the design of ambipolar metal oxides are discussed.