Min, JihongJihongMinDei Tos, IreneIreneDei TosRahimisheikh, SepidehSepidehRahimisheikhde la Fuente, BeatrizBeatrizde la FuenteRajagopal, DevikaDevikaRajagopalD'Haen, JanJanD'HaenCornil, DavidDavidCornilHauffman, TomTomHauffmanAernouts, TomTomAernoutsBeljonne, DavidDavidBeljonneHadermann, JokeJokeHadermannShin, ByunghaByunghaShinVermang, BartBartVermangShukla, SudhanshuSudhanshuShukla2026-09-092026-09-0920262198-3844https://imec-publications.be/handle/20.500.12860/60295<jats:title>ABSTRACT</jats:title> <jats:p> Solar‐driven photoelectrochemical (PEC) production of chemical fuels such as hydrogen is a viable solution to address climate neutrality objectives. Development of a monolithic tandem PEC device consisting of ideal bandgap absorbers is of paramount importance to realize efficient artificial photosynthesis systems. Herein, we report monolithic integration of Sb <jats:sub>2</jats:sub> S <jats:sub>3</jats:sub> on textured silicon to realize a completely inorganic and fully vacuum processed multilayer PEC device with Ag/Indium Tin Oxide (ITO)/Heterojunction with Intrinsic Thin layer (HIT) Si/ITO/Au/Sb <jats:sub>2</jats:sub> S <jats:sub>3</jats:sub> /NiO <jats:sub>x</jats:sub> architecture. Photoelectron spectroscopy and computational analysis show a staggered band alignment between Si and Sb <jats:sub>2</jats:sub> S <jats:sub>3</jats:sub> , emulating Z‐scheme charge transfer mechanism. We demonstrate a high performing and stable Sb <jats:sub>2</jats:sub> S <jats:sub>3</jats:sub> ‐Si monolithic tandem for PEC hydrogen evolution reaction (HER) coupled to iodide oxidation reaction (IOR). Under AM 1.5G illumination, the Sb <jats:sub>2</jats:sub> S <jats:sub>3</jats:sub> ‐Si monolithic tandem device achieves unassisted photocurrent density of 4.38 mA cm <jats:sup>−</jats:sup> <jats:sup>2</jats:sup> with faradaic efficiency of 97% for hydrogen, while maintaining ∼90% of its initial performance after 10 h of continuous operation. These results set a new benchmark for all inorganic monolithic tandems for efficient and sustainable solar‐to‐chemical conversion. This work unlocks the pathway for artificial photosynthesis systems comprising ideal bandgap photo absorbers. </jats:p>engJournal article10.1002/advs.75798WOS:001771716100001UNASSISTED SOLARSILICONPERFORMANCEMEDLINE:421707402198-3844