A Novel Thermochemical Metal Halide Treatment for High-Performance Sb₂Se₃ Photocathodes

The fabrication of cost-effective photostable materials with optoelectronic properties suitable for commercial photoelectrochemical (PEC) water splitting represents a complex task. Herein, we present a simple route to produce Sb₂Se₃ that meets most of the requirements for high-performance photocathodes. Annealing of Sb₂Se₃ layers in a selenium-containing atmosphere persists as a necessary step for improving device parameters; however, it could complicate industrial processability. To develop a safe and scalable alternative to the selenium physical post-processing, we propose a novel SbCl₃/glycerol-based thermochemical treatment for controlling anisotropy, a severe problem for Sb₂Se₃. Our procedure makes it possible to selectively etch antimony-rich oxyselenide presented in Sb₂Se₃, to obtain high-quality compact thin films with a favorable morphology, stoichiometric composition, and crystallographic orientation. The treated Sb₂Se₃ photoelectrode demonstrates a record photocurrent density of about 31 mA cm^-2 at -248 mV against the calomel electrode and can thus offer a breakthrough option for industrial solar fuel fabrication.