First-Principles Study of Polarons in Multiple Crystal Phases of Bismuth Vanadate

Bismuth vanadate (BiVO4) is a promising photocatalyst existing in multiple crystal phases, whose performance is critically influenced by charge carrier (polaron) behavior. Although polarons in monoclinic BiVO4 have been extensively studied, a comparative understanding of polaron behavior in its main crystal phases, including monoclinic scheelite, tetragonal zircon type, and tetragonal scheelite, is essential for optimizing photocatalytic efficiency. This study systematically investigates electron and hole polarons in these three BiVO4 phases using ab initio calculations. We find distinct polaron characteristics: electron polarons are consistently identified as Holstein type, whereas hole polarons are of the Fröhlich type in all three crystal structures. Our analysis reveals that although holes in all phases are scattered by longitudinal optical phonons of approximately 30 meV, variations in scattering strength lead to differing hole mobilities. The microscopic origins of these mobility differences are elucidated through analysis of dielectric tensors and Born effective charges. This work uncovers the mechanism by which crystal structure modulates polaron properties, offering crucial theoretical guidance for designing high-efficiency BiVO4-based photofunctional materials.