Operando IR Optical Control of Localized Charge Carriers in BiVO4 Photoanodes

In photoelectrochemical cells (PECs) the photon-to-currentconversionefficiency is often governed by carrier transport. Most metal oxidesused in PECs exhibit thermally activated transport due to charge localizationvia the formation of polarons or the interaction with defects. Thisimpacts catalysis by restricting the charge accumulation and extraction.To overcome this transport bottleneck nanostructuring, selective dopingand photothermal treatments have been employed. Here we demonstratean alternative approach capable of directly activating localized carriersin bismuth vanadate (BiVO4). We show that IR photons canoptically excite localized charges, modulate their kinetics, and enhancethe PEC current. Moreover, we track carriers bound to oxygen vacanciesand expose their & SIM;10 ns charge localization, followed by & SIM;60 & mu;s transport-assisted trapping. Critically, we demonstrate thatlocalization is strongly dependent on the electric field within thedevice. While optical modulation has still a limited impact on overallPEC performance, we argue it offers a path to control devices on demandand uncover defect-related photophysics.

Automated summary

In photoelectrochemical cells (PECs), carrier transport plays a significant role in photon-to-current conversion efficiency. Many metal oxides used in PECs exhibit thermally activated transport due to charge localization and interaction with defects, which affects catalysis. To improve transport efficiency, nanostructuring, selective doping, and photothermal treatments have been used. This study demonstrates a novel approach to directly activate localized carriers in bismuth vanadate (BiVO4) using infrared photons. The results show that optical excitation of localized charges enhances PEC current by modulating their kinetics. This research provides insights into defect-related photophysics and offers a possible method for device control.