Sulfur‐Supplemented Vapor Transport Deposition of Sb2S3 and Sb2(S,Se)3 for High‐Performance Hydrogen Evolution Photocathodes

Chalcogen vacancy has long been recognized as a detrimental deep‐level defect that can induce severe charge recombination and diminish the quasi‐Fermi‐level splitting in Sb 2 S 3 and Sb 2 Se 3 , especially when they are prepared by physical vapor deposition in vacuum. In order to counter this limitation, a sulfur‐supplemented vapor transport deposition technique is proposed, which intentionally introduces low pressure sulfur vapor and can thus afford low‐defect‐density antimony chalcogenide films. The resultant photocathodes modified with conformal TiO 2 protection layer and Pt cocatalyst demonstrate a photocurrent as high as 20 mA cm −2 along with a much improved fill factor and onset potential, achieving an applied bias photoconversion efficiency above 1%. This work highlights the importance of the vacancy defect passivation and the preferential crystalline orientation in the film in promoting the photocathode performance.