Thin-Film Materials for the Protection of Semiconducting Photoelectrodes in Solar-Fuel Generators

TLDR

Electrochemical instability of semiconductor photoelectrodes in aqueous electrolytes hampers the development of robust sunlight‑driven water‑splitting systems. This review examines protective thin films that enhance the electrochemical stability of unstable semiconductor photoelectrodes such as Si and GaAs, and outlines future directions for thin‑layer protection in solar‑fuel production. The authors discuss the origins of instability, strategies for stable photoelectrodes, and focus on thin protective films applied to photoanodes and photocathodes for oxygen evolution, halide oxidation, and hydrogen evolution.

Abstract

The electrochemical instability of semiconductors in aqueous electrolytes has impeded the development of robust sunlight-driven water-splitting systems. We review the use of protective thin films to improve the electrochemical stability of otherwise unstable semiconductor photoelectrodes (e.g., Si and GaAs). We first discuss the origins of instability and various strategies for achieving stable and functional photoelectrosynthetic interfaces. We then focus specifically on the use of thin protective films on photoanodes and photocathodes for photosynthetic reactions that include oxygen evolution, halide oxidation, and hydrogen evolution. Finally, we provide an outlook for the future development of thin-layer protection strategies to enable semiconductor-based solar-driven fuel production.