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

Abstract

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.