Post‐Synthetic Silver Ion and Sulfurization Treatment for Enhanced Performance in Sb2Se3 Water Splitting Photocathodes

Abstract In the past decade, antimony selenide (Sb 2 Se 3 ) has made significant progress as a solar energy conversion material. However, the photovoltage deficit continues to pose a challenge and is a major hurdle that must be overcome to reach its maximum solar conversion efficiency. In this study, various post‐synthetic treatments are employed, of which the combination of a solution phase silver nitrate treatment and sulfurization has shown to be the most effective approach to mitigate the photovoltage deficit in this Sb 2 Se 3 ‐based device. A significant enhancement in the photovoltage is observed after the treatments, as evident by the increase in the onset potential from 0.18 to 0.40 V versus reversible hydrogen electrode. Multiwavelength Raman shows that combining these two treatments removes amorphous Se and metallic Sb from the surface and yields a high‐quality surface layer of Sb 2 (S 1−x , Se x ) 3 on the bulk Sb 2 Se 3 photoabsorber layer. X‐ray photoelectron spectroscopy with depth profiling reveals extensive incorporation of silver into the film. Density functional theory calculations suggest that silver ions can intercalate between the [Sb 4 Se 6 ] n ribbons and remain in the Ag + state. This effective treatment combination brings the practicality of the Sb 2 Se 3 photocathode for water splitting one step closer to large‐scale applications.