Dynamic Sulfur Reservoir Programs Cation-Exchange Kinetics in PbS Quantum Dots for Short-Wave Infrared Imaging Chips

Cation-exchange synthesis produces monodisperse PbS quantum dots (QDs), yet its central limitation─precursor preparation and dropwise injection─is usually treated as a practical issue. Here, we recast it as sulfur chemical-potential programming; that is, ethyl ziram (EZ) serves as a dynamic sulfur reservoir (DSR) whose thermolysis continuously evolves sulfur activity during growth. This reservoir couples ZnS QD seeds with reservoir-fed growth, shifting the reaction from externally injected templates to an internally regulated kinetic regime, where QD size is set by the balance between seed density and EZ-derived sulfur replenishment. The DSR route yields short-wave infrared PbS QDs tunable from 1200 to 2200 nm, with narrow size distributions, high reproducibility, and reduced synthetic burden. Photodetectors show 64.7% external quantum efficiency and 5.8 × 1012 Jones detectivity, and 640 × 512 CMOS-integrated imaging chips exhibit a 0.04% bad-pixel rate and 3.78% photoresponse nonuniformity, validating DSR as a strategy for high-quality QD synthesis.