Computational Study Revealing the Influence of Surface Phenomena in p-GaAs Water-Splitting Cells

A computational model of a photoelectrochemical cell describing the influence of competing surface reactions to the operation of the cell is presented. The model combines an optical simulation for the incident light intensity with fully self-consistent solution of drift-diffusion equations to accurately calculate the electronic state of the semiconductor electrode in a photoelectrochemical cell under operation. The solution is calculated for the full thickness of a typical wafer, while simultaneously solving the thin surface charge region with sufficient precision. In addition to comparing the simulated current–voltage response with experimental data, the simulation is shown to replicate experimental results from electrochemical impedance spectroscopy (EIS) measurements. The results show that considering optical losses in the system is crucial for accurate simulation. The model is capable of selectively characterizing the impact of material parameters on both current–voltage response and interface capacitance, while revealing the internal dynamics of the quasi-Fermi levels that are inaccessible by experimental methods.