Heterostructure CsPbBr₃/SrBrF Nanocrystals Stabilize Perovskite LEDs with Suppressed Halogen Ion Migration

Ion migration is a fundamental problem for perovskite nanocrystal-based light-emitting diodes (PNC-LEDs)─a forerunner in next-generation displays and lighting technologies. Here, we report on monodisperse heterostructure CsPbBr 3 perovskite nanocrystals capped with satellite SrBrF nanocrystals for stabilized and improved PNC-LEDs. We show that capping SrBrF can passivate surface carrier traps and improve the photoluminescence quantum yields of CsPbBr 3 nanocrystals from 43.3% to 89.0%, showing about a 28-fold improvement in thermal stability (at 363 K) and exceptional photostability under long-term ultraviolet exposure (at 365 nm). The fabricated PNC-LEDs show significantly improved external quantum efficiency (EQE) (18.5%, 80-fold higher), maximum luminance (1604 cd/m 2, 3-fold higher), and half-life (28 min, 14-fold higher), compared with the one fabricated with unmodified CsPbBr 3 nanocrystals. Time-of-flight secondary-ion mass spectrometry (TOF-SIMS) studies gave compelling evidence of inhibited halogen ion migration in CsPbBr 3 /SrBrF PNC-LEDs due to the capping of SrBrF nanocrystals. This approach has important implications for fabricating high-performance PNC-LEDs with suppressed halogen ion migration.