Researchers from Tsinghua University and Beijing Institute of Technology have developed an ion-pair pinning strategy that enables the fabrication of high-performance perovskite quantum dot light-emitting diodes (QLEDs) under ambient air conditions - an important step toward cost-effective, large-scale production of next-generation display and lighting technologies.
a Schematic structure, b cross-sectional SEM image, and c energy diagram of the device. Image from: Light: Science & Applications
Traditionally, the emissive perovskite quantum dot (QD) layers used in QLEDs must be processed in inert gas atmospheres to avoid degradation from moisture and oxygen. This requirement hinders manufacturing scalability and increases costs. To overcome this, the team introduced tetraalkylammonium triflate (NR₄OTf) into the precursor solution to stabilize and passivate formamidinium lead bromide (FAPbBr₃) QD films during air processing.
The team found that the trifluoromethanesulfonate anions (OTf⁻) form hydrogen bonds with FA⁺ cations, effectively preventing their detachment and simultaneously passivating uncoordinated Pb²⁺ sites on the QD surface. In parallel, the tetraalkylammonium cations (NR₄⁺) act as X-type ligands, suppressing deprotonation and binding strongly to the QD lattice. This dual pinning mechanism stabilizes the crystal structure and shields the QDs from oxygen and moisture, allowing for excellent film uniformity and enhanced optoelectronic properties even under ambient conditions.
Using this method, the air-processed perovskite QLED achieved a maximum external quantum efficiency (EQE) of 21.3% and a peak luminance of 30,683 cd·m⁻², emitting a pure-green light at 529 nm with a narrow full width at half maximum (FWHM) of 21 nm. The color coordinates (0.19,0.76) satisfy the Rec. 2020 standard for display applications. For comparison, devices fabricated in nitrogen atmosphere reached EQEs up to 23.9% and peak luminances of over 83,000 cd·m⁻², showcasing the exceptional potential of this approach under both conditions.
By eliminating the dependence on inert gas environments, this ion-pair pinning strategy marks a major advance in the scalable production of perovskite-based optoelectronics. The approach not only stabilizes QD films during air fabrication but also improves their photoluminescence and operational stability - issues that have long limited perovskite industrialization.
The team anticipates that this strategy will open new avenues for developing low-cost, high-efficiency perovskite QLEDs suitable for commercial displays, lighting, and beyond.
