Equivalent Circuit of Electrons and Holes in Thin Semiconductor Films for Photoelectrochemical Water Splitting Applications

A simple model for the kinetics of electrons and holes in a thin semiconductor film in photoelectrochemical water splitting conditions is discussed, with a focus to discriminate between trap-assisted recombination and charge-transfer processes. We formulate the kinetic model in terms of the measurements of impedance spectroscopy and discuss the application of the results for the interpretation of the current potential curve under photogeneration. We provide a rigorous structure of the fundamental equivalent circuit for photoelectrochemical water splitting systems including a new predicted feature that is a chemical capacitance of the minority carriers that can give rise, in combination with other standard features, to a total of three arcs in the complex plane.