Exploring the electronic structure of BiVO4 thin films using energy-resolved electrochemical impedance spectroscopy

Bismuth vanadate (BiVO4) is a promising photoelectrochemical water-splitting semiconductor. This study focuses on elucidating the electronic structure of BiVO4 by analyzing energy-resolved electrochemical impedance spectroscopy (ER-EIS) data. The primary objective is to demonstrate the effectiveness of the ER-EIS, which is typically applied to organic semiconductors, in estimating the band edge positions of BiVO4 films deposited on FTO substrates. The impedance spectra analysis as a function of an applied overpotential permits an estimation of the density of states, where the limits correspond to the valence (VB) and conduction band (CB) edge positions that determine the redox reactions the semiconductor can promote. The energy difference between the CB and VB corresponds to the material's band gap (Eg). The calculated Eg using ER-EIS closely matches the reported optical properties of the material, and the energy positions of the VB and CB align with the reported values for BiVO4.