Synergistic Silver Doping and Halide Passivation for Enhanced Stability and Emission Efficiency in CsPbI ₃ Quantum Dots

The intrinsic instability of CsPbI3 quantum dots (QDs) presents a major challenge for their practical deployment in optoelectronic devices. Here, we demonstrate the combined effects of Ag+ doping and halide (Cl–/I–) passivation to enhance the structural and optical stability of CsPbI3 QDs. Partial substitution of Pb2+ by Ag+ leads to lattice contraction and defect suppression, while Cl– acts as a surface-localized passivating agent. Structural analyses (X-ray diffraction, high-resolution transmission electron microscopy, and high-resolution scanning transmission electron microscopy) confirm successful Ag+ incorporation without secondary phase formation, and X-ray photoelectron spectroscopy depth profiling reveals surface enrichment of Cl–. Mixed doping with AgCl and AgI precursors effectively stabilizes the cubic perovskite phase, increasing the photoluminescence quantum yield (PLQY) from ∼85 to 96.6% and reducing nonradiative recombination, as supported by time-resolved photoluminescence measurements. The optimized CsPb1–xAgxI3 (x = 0.025 AgCl + 0.025 AgI) exhibits outstanding photostability, retaining ∼41% of its initial PLQY after 70 days of continuous ultraviolet exposure. When integrated into red-emitting light-emitting diode devices, these QDs deliver external quantum efficiencies up to 36.8%, with stable and saturated emission. These results establish Ag+/halide codoping as a powerful strategy to advance CsPbI3 QDs toward robust and high-performance optoelectronic applications.