Visualization of Synthesis-Dependent Trapped Charge Carrier Behavior in BiVO4 and Its Relation to the Performance

Abstract

Understanding charge carrier dynamics is crucial for optimizing the performance of BiVO₄-based photoanodes used in solar water splitting. In this study, we investigated the spatiotemporal behavior of charge carriers in BiVO₄ films synthesized by three distinct methods: electrodeposition (ED), hydrothermal decomposition (HT), and metal–organic decomposition (MOD). Using patterned-illumination time-resolved phase microscopy (PI–PM), we selectively visualized trapped charge carriers with micrometer spatial resolution and nanosecond-to-millisecond temporal behavior. Clustering analyses based on time-resolved refractive index changes allowed us to differentiate between electron and hole dynamics across the samples. The ED sample showed electron accumulation dominance at the surface and the highest charge separation efficiency, consistent with its strong (040) facet growth. The MOD sample exhibited superior hole injection efficiency due to its fine-grained morphology, while the HT sample provided a balanced performance with moderate charge separation and transfer efficiencies. These findings demonstrate that the synthetic method has a pronounced impact on charge carrier behavior and interfacial processes.