Competing Self-Trapped Exciton States and Multiple Emission Pathways in BiVO.

Transition metal oxides, such as BiVO, have attracted significant attention for their potential in photoelectrochemical water-splitting. BiVO, a model material in this area, is prone to charge localization in the form of small polarons. Recently, self-trapped excitons (STEs) in BiVO have been experimentally observed, but their precise nature remains elusive. In this study, we employ time-dependent density functional theory (TD-DFT) with a nonempirical PBE0(α) hybrid functional to investigate the localization, stability, and optical properties of STEs in BiVO. Our results reveal two distinct localized exciton configurations with comparable energies. We show that the emission from a single STE configuration leads to multiple peaks in the emission spectrum, originating from different types of internal transitions. The positions of peaks in the calculated optical spectra are in good agreement with experimental observations.