image: Precisely tailored Zn1−xCdxSe/ZnSe shells with a continuous gradient structure were synthesized using the facile high-temperature successive ion layer adsorption and reaction (HT-SILAR) strategy. This process enables the formation of large-particle alloyed red CdZnSe/Zn1−xCdxSe/ZnSe/ZnS/CdZnS QDs. The obtained QDs exhibit an ultra-narrow FWHM of 17.1 nm and a near-unity PLQY, resulting in a record EQE of 38.2% and an exceptional T95 lifetime of over 21,000 hours (tested at 1000 cd m–2) for red QLEDs.
Credit: ©Science China Press
Quantum dot light-emitting diodes (QLEDs) have made rapid progress in luminescence, efficiency, and stability, making them promising candidates for displays and solid-state lighting applications. However, achieving high-performance QLEDs with high color purity remains a persistent challenge, particularly red QLEDs, thus limiting the popularity of ultra-high definition devices. Recently, Soochow University, in collaboration with Macau University of Science and Technology and other research institutes, reported a facile high-temperature successive ion layer adsorption and reaction (HT-SILAR) strategy for the growth of high-quality, large-particle, alloyed red QDs. These QDs exhibit a near-unity photoluminescence quantum yield (PLQY), and narrow emission with a full width at half maximum (FWHM) of 17.1 nm. As a result, a record external quantum efficiency (EQE) 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 hours were achieved for QLEDs. This work opens new avenues for synthesizing high-quality QDs with high color purity and was published in Science Bulletin.
Facile Tailored Synthesis Strategy
The research team adopted a facile tailored high-temperature successive ion layer adsorption and reaction (HT-SILAR) strategy for the synthesis of gradient alloyed QDs. This customized approach allows for precise control over the growth of the CdZnSe/Zn₁₋ₓCdₓSe/ZnSe/ZnS/CdZnS structure. By tailoring the Zn₁₋ₓCdₓSe/ZnSe shell thicknesses, the strategy effectively alleviates compressive strain, suppresses heavy-hole (hh) energy band splitting, and weakens exciton-phonon coupling, thereby enhancing luminescence color purity. Additionally, the design of the Zn₁₋ₓCdₓSe/ZnSe/ZnS shells confines carriers within the luminescent core, boosting the photoluminescence quantum yield (PLQY). Finally, the Cd-doped ZnS shells passivate surface defects and facilitate hole injection, achieving more balanced carrier recombination in the QLEDs.
Excellent Device Performance.
Thanks to the successful synthesis of high-quality, large-particle QDs and highly efficient carrier injection, the QLEDs exhibit exceptional electroluminescence performance. Specifically, the peak external quantum efficiency (EQE) reaches an impressive 38.2%, with brightness surpassing 120,000 cd/m² at a driving voltage of 6 V. Furthermore, at a brightness level of 1,000 cd/m², the device demonstrates an operational lifetime exceeding 24,000 hours, which translates to reliable performance for up to eight years under daily usage of eight hours. The use of large-size QDs also significantly reduces heat generation within the device, mitigating the risk of screen "burn-in" and enhancing the overall stability. This, in turn, ensures a robust and durable user experience.