(617ey) Engineering Interfaces for the Activation and Stabilization of Photovoltaic-Grade Thin Film Light Absorbers for Photoelectrochemical Hydrogen Production
The chalcopyrite class of materials has shown promise for photovoltaic (PV) applications given these materialsâ?? utility as potentially scalable and bandgap-tunable thin film light absorbers. Accordingly, Dr. Gaillardâ??s group has developed thin films of CuGa(S,Se)2 that approach the ideal bandgap for the front absorber in a tandem dual-absorber array for PEC; as a p-type semiconductor, these films function well as photocathodes for carrying out the hydrogen evolution reaction (HER). However, the material is neither intrinsically stable in aqueous electrolyte nor intrinsically active as an HER catalyst. Accordingly, attempts have been made to activate and stabilize the photocathodes using thin films of oxides (such as TiO2) and sulfides (like MoS2) that have proven valuable as either protection layers, electrocatalysts, or both. Mechanisms for degradation have been probed via post-mortem electron microscopy and elemental analysis. Furthermore, work has been conducted to investigate the incorporation of n-type emitter layers (such as CdS and ZnOS) in order to maximize the photovoltage produced by the photoelectrode array.