Researchers from the University of Electronic Science and Technology of China, Harbin Engineering University, Peking University and Soochow University have reported an advance in blue perovskite quantum dot light-emitting diodes (QLEDs), achieving record-high efficiency with minimal roll-off and excellent spectral stability. By introducing a multifunctional molecule passivation strategy based on 1‑ethyl‑3‑methylimidazolium hexafluorophosphate (EMIMPF₆), the team effectively suppressed multiple non-radiative decay pathways that have long limited blue perovskite QLED performance.
The [PF₆]⁻ anions in EMIMPF₆ coordinate strongly with lead dangling bonds and cesium sites, substantially reducing defect-assisted carrier loss and mitigating inter-dot electronic coupling. Complementarily, the [EMIM]⁺ cations interact with bromine vacancies and modulate band alignment, optimizing hole injection and improving charge balance under operating bias. This synergistic dual-ion passivation also increases the dielectric constant of the active layer, which suppresses Auger recombination - a major contributor to efficiency roll-off in high-brightness operation.
As a result, the treated quantum dot films exhibit a pronounced increase in photoluminescence quantum yield, rising from 78% to 92%, and deliver narrow, high-purity blue emission centered at 472 nm (CIEy = 0.091). The resulting QLEDs reach a record external quantum efficiency (EQE) of 20.02% at a luminance of 6441 cd m⁻², while maintaining an impressive 18.47% EQE even at 9587 cd m⁻²—virtually eliminating the efficiency roll-off typically observed beyond 4000 cd m⁻². Operational stability also improves by an order of magnitude compared with previous reports, with stable emission spectra maintained throughout extended operation.
This work presents a mechanism by which multifunctional ionic species simultaneously stabilize perovskite quantum dot surfaces, passivate deep traps, reduce inter-dot coupling, and enhance charge transport properties. The approach provides a general design principle for improving the optoelectronic performance of perovskite emitters across the visible spectrum. By uniting high efficiency, strong spectral stability, and robust operational durability, the study marks a step toward commercially viable ultra‑high‑definition blue QLED displays and energy-efficient photonic devices.
