Thiol‐Mediated Compositional Control and Coherent Shelling of Ag‐In‐Ga‐S Quantum Dots for High‐Performance Light Emitting Diodes

ABSTRACT The pursuit of heavy‐metal‐free colloidal quantum dots (QDs) with simultaneous high brightness and narrow emission remains a fundamental challenge for the next‐generation displays. I‐III‐VI ₂ ‐based AgInGaS ₂ (AIGS) QDs have garnered significant attention due to their facile composition‐tunable emission across the visible region. The advanced synthetic technologies have unveiled green‐emitting AIGS QDs with vivid and narrowband emission. However, notable tail emission and poor electroluminescent device performance remain unresolved. Herein, green‐emitting AIGS QDs with exceptional optical purity are synthesized through thiol‐mediated composition regulation combined with coherent AgGaS ₂ (AGS) shell formation. The synergistic effects of core composition tuning and coherent AGS shell growth effectively suppress the structural and interfacial defects, resulting in a high photoluminescence quantum yield (PLQY) of 88% and a narrow emission linewidth with full‐width at half‐maximum (FWHM) of 30 nm with complete absence of defect‐induced tail emission. When integrated into QD‐based light‐emitting diodes (QLEDs), these AIGS/AGS QDs yield a record‐high external quantum efficiency (EQE) of 8.4% and a luminance of 7906 cd/m ² among I‐III‐VI ₂ heavy‐metal‐free green emitters, while maintaining excellent spectral purity under electrical excitation. These results demonstrate the great potential of AIGS/AGS QDs as environmentally friendly, high‐performance alternatives for advanced display technologies.