Intrinsic Defect Self-Compensation Enables Spectrum Narrowing of Uniform Alloyed Ag–In–Ga–S Quantum Dots

Eco-friendly Ag–In–Ga–S (AIGS) quantum dots (QDs) are promising alternatives to toxic Pb/Cd-containing QDs due to their tunable emission, high photoluminescence quantum yield (PLQY), and solution processability. However, their intrinsic defect-driven broad emission limits applications in high-resolution displays. Herein, we report a synthesis of uniform alloyed AIGS QDs with narrow emission via defect self-compensation, circumventing intricate shell growth. Benefiting from the defect compensation of interstitial Ag (Agi) to Ag vacancy (VAg) under thermal activation, structural defects are significantly suppressed, achieving tunable emission with remarkably narrow full width at half-maximum (fwhm = 30–38 nm) and high PLQYs. The resulting quantum dot light-emitting diodes (QLEDs) exhibit electroluminescence with fwhm < 40 nm, validating high-purity display compatibility. The simplified approach and mechanistic clarity advance the production of high-color-purity AIGS QLEDs, offering a paradigm for narrow emission in eco-friendly I–III–VI QDs.