Surface\nEngineering of Environment-Friendly Ag-In‑S\nQuantum Dots for Stable and Efficient Photoelectrochemical Cells

Environment-friendly colloidal Ag-In-S (AIS) quantum\ndots (QDs)\nhave exhibited facilely tunable optical properties enabled by flexible\nchemical composition. However, their application in solar energy conversion,\nparticularly in photoelectrochemical (PEC) H<sub>2</sub> production\ncells, still shows low performance due to severe charge recombination\ninduced by the intragap/surface defects from various lattice vacancies\nand substitutions of QDs. Herein, an advanced surface engineering\nstrategy of gallium (Ga) regulated by sulfur (S) was developed to\nmitigate the charge trapping states of AIS QDs. Such Ga/S-treatment\noptimized the photoexcited carriers’ dynamics of QDs and led\nto improved charge transfer efficiency in a PEC cell, showing a photocurrent\ndensity as high as 8.4 mA cm<sup>–2</sup> with outstanding\noperational stability under 1 sun AM 1.5G illumination (100 mW cm<sup>–2</sup>). The results validate that surface passivation via\nGa/S is a promising route for engineering the optoelectronic properties\nof I-III-VI QDs toward high-performing solar-to-fuel conversion applications.