(Zn,Ti)O Electron Transport Layer Enables the Highest Conversion Efficiency in Cd‐Free Sb <sub>2</sub> Se <sub>3</sub> Photocathodes for Stable Solar Hydrogen Production
Shuo Chen, Yong Chen, Hanhua Zhang, Muhammad Abbas, Donglou REN, Yuexing Chen, Jingting Luo, Zhuanghao Zheng, Zhenghua Su, Guangxing Liang
Abstract
ABSTRACT Antimony selenide (Sb 2 Se 3 ) has emerged as a promising photocathode material for photoelectrochemical (PEC)‐driven solar hydrogen production due to its low toxicity, cost‐effectiveness, and excellent photoelectric properties. Currently, efficient Sb 2 Se 3 photocathodes are mostly coupled with CdS electron transport layer (ETL), however, suffering from natural toxicity, parasitic light absorption, and interfacial mismatch and/or instability. In this study, we introduce a Cd‐free Sb 2 Se 3 photocathode with an atomic layer deposition‐processed (Zn,Ti)O ETL, which mitigates the respective limitations of binary oxides (i.e., ZnO and TiO 2 ). The optimized (Zn,Ti)O ETL enhances electron carrier density, establishes a favorable ‘spike‐like’ band alignment at the Sb 2 Se 3 /(Zn,Ti)O interface, significantly improves charge separation and transport efficiencies, as well as the stability. Consequently, the champion device achieves an impressive photocurrent density ( J ph ) of 31.1 mA/cm 2 , a record half‐cell solar‐to‐hydrogen (HC‐STH) efficiency of 5.27% for Cd‐free Sb 2 Se 3 photocathodes, and the highest unbiased STH efficiency of 2.50% in the Sb 2 Se 3 ‐BiVO 4 tandem cell, setting a new benchmark for eco‐friendly and high‐performance PEC processed green hydrogen production.