Utilizing modeling, experiments, and statistics for the analysis of water-splitting photoelectrodes†

A multi-physics model of a planar water-splitting photoelectrode was developed, validated, and used to identify and quantify the most significant materials-related bottlenecks in photoelectrochemical device performance. The model accounted for electromagnetic wave propagation within the electrolyte and semiconductor, and for charge carrier transport within the semiconductor and at the semiconductor– electrolyte interface. Interface states at the semiconductor–electrolyte interface were considered using an extended Schottky contact model. The numerical model was validated with current–voltage measurements using an n-type GaN photoanode immersed in 1 M H2SO4. Numerical design of experiments and parametric analysis were conducted using the validated model in order to identify and optimize the key factors for water-splitting photoelectrodes. The methodology, developed using an experimentally-validated numerical model coupled to statistical analysis, provides a general approach to identify and quantify the main material challenges and design considerations in working PEC devices. In the case of n-type GaN, the surface recombination, flatband potential, and doping concentration were identified as the most significant parameters for the photocurrent density.