Photoelectrochemical water splitting offers a green approach for hydrogen production, but its efficiency is limited by the lack of suitable photoelectrode materials for water oxidation and reduction reactions. Metal oxides demonstrate exceptional stability in aqueous electrolytes, but those with band gaps optimised for visible light typically have open d shell configurations and suffer from low photoconversion efficiencies. Unlike in conventional semiconductors where absorbed photons generate mobile electrons and holes, in metal-oxides with open d shell configuration, many of the absorbed photons give rise to localized electronic transitions that do not generate charge carriers that contribute to the photocurrent.
The goal of DREAM is to address this challenge and provide a leap forward in understanding the photogeneration processes in metal-oxide photoelectrodes and their effect on photoconversion efficiency. To achieve these goals, we couple systematic control of crystallographic structure, d orbital occupancy, and local cation environment using heteroepitaxial thin film growth together with wavelength and temperature-resolved characterization of the photogeneration yield spectrum. The knowledge gained by these fundamental investigations is expected to lead to new design rules, which will be employed to engineer new metal-oxides with near unity photogeneration yield, and integrate them into novel device architectures, enabling highly efficient PEC-PV tandem cells for unassisted solar water splitting.
