# Competing Self-Trapped Exciton States and Multiple Emission Pathways in BiVO4

## TL;DR

This paper explores the nature of self-trapped excitons in BiVO4 using advanced theory, revealing multiple emission pathways and configurations.

## Contribution

The study introduces a nonempirical hybrid functional approach to uncover distinct exciton states and their optical behavior in BiVO4.

## Key findings

- Two distinct localized exciton configurations with comparable energies were identified.
- A single exciton configuration leads to multiple emission peaks from internal transitions.
- Calculated optical spectra align well with experimental observations.

## Abstract

Transition metal
oxides, such as BiVO4, have
attracted
significant attention for their potential in photoelectrochemical
water-splitting. BiVO4, a model material in this area,
is prone to charge localization in the form of small polarons. Recently,
self-trapped excitons (STEs) in BiVO4 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 BiVO4. 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.