Surface Engineering of Environment-Friendly Ag-In-S Quantum Dots for Stable and Efficient Photoelectrochemical Cells

Environment-friendly colloidal Ag-In-S (AIS) quantum dots (QDs) have exhibited facilely tunable optical properties enabled by flexible chemical composition. However, their application in solar energy conversion, particularly in photoelectrochemical (PEC) H2 production cells, still shows low performance due to severe charge recombination induced by the intragap/surface defects from various lattice vacancies and substitutions of QDs. Herein, an advanced surface engineering strategy of gallium (Ga) regulated by sulfur (S) was developed to mitigate the charge trapping states of AIS QDs. Such Ga/S-treatment optimized the photoexcited carriers' dynamics of QDs and led to improved charge transfer efficiency in a PEC cell, showing a photocurrent density as high as 8.4 mA cm–2 with outstanding operational stability under 1 sun AM 1.5G illumination (100 mW cm–2). The results validate that surface passivation via Ga/S is a promising route for engineering the optoelectronic properties of I-III-VI QDs toward high-performing solar-to-fuel conversion applications.