Crystal growth promotion and interface optimization enable highly efficient Sb2Se3 photocathodes for solar hydrogen evolution

Antimony selenide (Sb2Se3) is an encouraging photocathode candidate that satisfies essential requirements for efficient solar hydrogen evolution, and also gains significant progress over the last few years. However, simultaneously achieving its satisfied photocurrent density (Jph) and onset potential (Von) remains a fundamental challenge. In this work, a thermodynamic/kinetic combination reaction process involving in-situ selenization of Sb precursor was established to synthesize a compact, large-grained, and preferentially [hk1]-oriented Sb2Se3 absorber layer. In parallel, indium (In3+) cation dopant was introduced to regulate both optical and electrical properties of CdS buffer layer. Such absorber and interface engineering exertions prospectively suppressed recombination losses and remarkably improved the planar-type Mo/Sb2Se3/CdS (In)/TiO2/Pt photocathode performance, owing to the enhanced charge carrier generation, separation, and transport. Consequently, the champion device delivers highly stimulating Jph of 35.7 mA cm−2, Von of 0.54 VRHE, also a record half-cell solar-to-hydrogen conversion efficiency of 5.6%, paving a bright avenue for its practical solar hydrogen evolution applications. [Display omitted] •Self-assembled growth of high-quality Sb2Se3 via in-situ selenization of Sb precursor.•In3+ cation dopant can regulate both optical and electrical properties of CdS.•It can enhance charge carrier generation/separation/transport, and suppress recombination.•Sb2Se3/CdS (In) photocathode delivers essential Jph of 35.7 mA cm−2 and Von of 0.54 VRHE.•Achieving a new record HC-STH conversion efficiency of 5.6% for Sb2Se3 photocathodes.