Understanding Nanoscale Heterogeneity of Photogenerated Charge Carriers in BiVO₄ Photoanodes by Conductive AFM

Bismuth vanadate (BiVO₄) is a promising oxide semiconductor for photoelectrochemical water splitting due to its moderate bandgap, favorable conduction band position, and long photocarrier lifetimes. However, the performance is limited by poor majority carrier transport, stoichiometry deviations, and structural defects leading to interfacial charge trapping and non-uniform energy landscapes. Identifying and controlling these nanoscale phenomena will enable the design of the next generation of highly efficient materials.
Here, we use photoconductive atomic force microscopy to resolve the correlation between local photocurrent, charge transport mechanisms, and morphology of polycrystalline BiVO₄ films. We find that by tuning the probe coating selective sensitivity to spatial surface or bulk heterogeneity can be achieved. In this context, we study the impact of temperature, environmental atmosphere, excitation energy and power on the local charge carrier transport. This careful analysis allows to identify the local charge transport and loss mechanisms in BiVO₄ which ultimately contribute to desired photocurrent generation or undesired side reactions.