Fully Textured Monolithic Sb2S3/Silicon Tandem for Unbiased and Stable Solar-Driven Water Splitting Paired with Iodide Oxidation Reaction

Abstract

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 Sb2S3 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/Sb2S3/NiOx architecture. Photoelectron spectroscopy and computational analysis show a staggered band alignment between Si and Sb2S3, emulating Z-scheme charge transfer mechanism. We demonstrate a high performing and stable Sb2S3-Si monolithic tandem for PEC hydrogen evolution reaction (HER) coupled to iodide oxidation reaction (IOR). Under AM 1.5G illumination, the Sb2S3-Si monolithic tandem device achieves unassisted photocurrent density of 4.38 mA cm- 2 with faradaic efficiency of 97% for hydrogen, while maintaining similar to 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.