Photoelectrochemistry at semiconductor-liquid interfaces is fundamental to the performance of solar-driven water-splitting materials. However, photoelectrochemical measurements are limited to providing information about majority carriers, not the minority carriers that are key to the reactivity of the semiconductor surface. Surface photovoltage spectroscopy is a sensitive, non-contactless technique providing information on photo-induced potential changes at surfaces and interfaces. In the following study, intensity-dependent surface photovoltage spectroscopy is used to determine the quasi-Fermi level splitting in a gallium phosphide wafer in contact with pure water, 0.01 M Na2SO3, and 0.01 M [Fe(CN)6]3-/[Fe(CN)6]4-. These results are paired with open circuit potential measurements to determine the local potential at the GaP surface in the presence of these aqueous redox couples. Results suggest that an Ef,p overpotential of 0.2 V or more is needed to oxidize the reducing agents tested here. This work offers predictions about suitable redox couples to pair with GaP. This work is expected to provide a generalizable method for gaining insights into the photoelectrochemical abilities and limitations of semiconductor single crystals.

Liquid surface photovoltage spectroscopy observes quasi-Fermi level splitting in GaP photoelectrodes

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.