Tailored large-particle quantum dots with high color purity and excellent electroluminescent efficiency

High-quality quantum dots (QDs) possess superior electroluminescent efficiencies and ultra-narrow emission linewidths are essential for realizing ultra-high definition QD light-emitting diodes (QLEDs). However, the synthesis of such QDs remains challenging. In this study, we present a facile high-temperature successive ion layer adsorption and reaction (HT-SILAR) strategy for the growth of precisely tailored Zn_1-xCd_xSe/ZnSe shells, and the consequent production of high-quality, large-particle, alloyed red CdZnSe/Zn_1-xCd_xSe/ZnSe/ZnS/CdZnS QDs. The transitional Zn_1-xCd_xSe/ZnSe shells serve to effectively suppress heavy hole energy level splitting and weaken the exciton-longitudinal optical phonon coupling of QDs, thus facilitating the formation of highly luminescent QDs with a near-unity photoluminescence quantum yield of 97.8% and narrow emission with a full width at half maximum of 17.1 nm. In addition, the introduction of transitional shells can extend the particle size of QDs to 19.0 nm, which is beneficial for efficient carrier recombination and reduced Joule heating in QD-based LEDs. As a result, the fabricated QLEDs can achieve a record external quantum efficiency of 38.2%, luminance over 120,000 cd m^-2, and exceptional operational stability T₉₅ (tested at 1,000 cd m^-2) of 24,100 h. These findings provide new avenues for synthesizing high-quality QDs with high color purity.