Analytical Model for Photocurrent-Voltage and Impedance Response of Illuminated Semiconductor/Electrolyte Interface under Small Voltage Bias

Semiconductor/electrolyte interfaces attract intense interest to convert solar energy to chemical fuels. Although many analytical models describing the photocurrent-voltage response of these devices exist, they have difficulty to reproduce full numerical simulations under small anodic bias. Herein, we derived an analytic model of a weakly absorbing n-type semiconductor/electrolyte interface with a slow rate of water oxidation reaction, fast recombination rate, and under small anodic bias. Excellent overlap of our model was demonstrated with full numerical simulations. The analytic model enabled us to derive an equation for impedance of the semiconductor/electrolyte interface in the dark and under illumination. The comparison of analytic and measured impedance allows to extract the reaction rate for redox reaction from the dark impedance and the direct bulk recombination constant of the semiconductor from the impedance under illumination.