Abstract
Light-emitting diodes based on perovskite nanocrystals (PNCsLEDs) have gained great interest for next-generation display and lighting technologies prized for their color purity, high brightness, and luminous efficiency which approach the intrinsic limit imposed by light extraction from the device structure. Although the time is ripe for the development of effective light outcoupling strategies to further boost the device performance, this technologically relevant aspect of PNC-LEDs is still without a definitive solution. Here, following theoretical guidelines and without the integration of complex photonic structures, we realize stable PNC-LEDs with external quantum efficiency (EQE) as high as 26.7%. Key to such performance is channeling the recombination zone in PNC emissive layers as thin as 10 nm, which we achieve by finely balancing charge transport using CsPbBr3 PNCs resurfaced with a nickel oxide layer. The ultrathin approach is general and, in principle, applicable to other perovskite nanostructures for fabricating highly efficient, color-tunable transparent LEDs.