We study oxygen vacancies in the tetragonal scheelite phase of bismuth vanadate and identify stable oxygen-deficient structures. Upon subjecting these to variable-cell optimization, we find that oxygen vacancies give rise to significant structural distortions, the degree of which exhibits a vacancy concentration dependence. Furthermore, we show that these distortions give rise to splitting of powder X-ray diffraction peaks, yielding patterns similar to that of the monoclinic scheelite phase, and that these effects are also present at finite temperatures. Our results highlight the need for characterization methods beyond X-ray diffraction for identifying the phase of synthesized bismuth vanadate samples and the importance of oxygen partial pressure control during synthesis.

We study the native defects in bismuth vanadate using hybrid density functional theory. We pay special attention to where excess charges localize by considering different polaronic distortions and find that charge localization has a profound effect on the local chemical environment around certain defects. In particular, oxygen dimerization may occur in the presence of acceptor defects. On the basis of Fermi level pinning due to compensation between donors and acceptors we additionally find that intrinsic p-type conductivity is difficult to achieve in BiVO 4 , in good agreement with experimental observations. Our results give new insights into the defect chemistry of bismuth vanadate and act as a guide for future studies on defects in complex metal oxides.

We study the nature of excess electrons in CsPbBr 3 and identify several single and double polaronic states. We emphasize the importance of proper inclusion of the self-interaction corrections for the stability of small electron polarons in this material. We demonstrate that spin−orbit coupling (SOC) has a significant impact on the energetics of the polaronic states. In particular, we find that SOC disfavors electron localization and leads to different polaronic geometries. Additionally, by carrying out thermodynamic integration, we show that small electron polarons are thermally stabilized in CsPbBr 3 . The small energy differences between the localized and delocalized electronic states could possibly reconcile the apparently conflicting properties of high charge-carrier mobilities and low recombinations rates.

Despite the vast investigations on improving the photoelectrochemical performance of BiVO4 for water splitting, charge recombination in the near-surface region remains a challenge. In this study, we showed that the...