Ligand-Mediated Compositional Co-optimization of AgInGaS/AgGaS Quantum Dots and Their Polymer Composites for White...

Ag-In-Ga-S (AIGS) quantum dots (QDs) are eco-friendly alternatives to Pb/Cd-based QDs, offering tunable emission, high photoluminescence quantum yield (PLQY), and solution-based processing. However, their practical performance is constrained by the reactivity mismatch among Ag, In, and Ga precursors, which can be rationalized by Hard and Soft Acids and Bases (HSAB) considerations, hindering Ga/In incorporation and causing defect-related broadening, along with poor thermal-humidity stability that degrades color purity and device lifetimes in WLEDs. We present a ligand-mediated compositional engineering strategy where tuning oleylamine (OLA) content during synthesis regulates precursor reactivity and Ga/In incorporation, enabling fine control of emission wavelength, line width, and PLQY. Growing a heteroepitaxial AgGaS₂ (AGS) shell on the AIGS QDs provides effective passivation, yielding AIGS/AGS core-shell QDs with significantly enhanced PLQY and narrowed emission. Furthermore, polymer encapsulation significantly enhances thermal-humidity stability, maintaining color purity and extending the operational lifetime. Combining blue LEDs with AIGS QDs and red QDs produces WLEDs with broad emission covering 106% of the NTSC color gamut and achieving 99.9% coverage, along with excellent operational stability (T₅₀ = 1060 min at 600 cd m^-2).