Multi‐Functional Interface‐Driven Defect Passivation Enabling High Efficiency and Stability in Vacuum‐Processed Perovskite Light‐Emitting Diodes

ABSTRACT Vacuum‐processed perovskite light‐emitting diodes (PeLEDs) hold great promise for large‐area, high‐resolution display technologies owing to their compatibility with scalable patterning and fabrication processes. However, their performance has been constrained by interfacial defects that induce non‐radiative recombination losses. Herein, we demonstrate highly efficient and stable CsPbBr 3 ‐based PeLEDs fabricated via evaporation through a multi‐functional interfacial engineering strategy that enables comprehensive defect passivation. A synergistic combination of phenylethylammonium bromide (PEABr), lithium bromide (LiBr), and (2‐(3,6‐dibromo‐9H‐carbazol‐9‐yl)ethyl)phosphonic acid (Br‐2PACz) is introduced to concurrently suppress halide vacancies, modulate crystallization kinetics, and passivate trap states in perovskite. Time‐resolved photoluminescence and space‐charge‐limited current analyses further confirm the prolonged exciton lifetime and reduced defect density. This cooperative effect enhances radiative recombination and carrier balance, resulting in a record external quantum efficiency (EQE) of 9.46% and a peak luminance of 21,931 cd m −2 , representing ∼135‐ and 49‐fold improvements compared with the pristine device (0.07% EQE and 446.7 cd m −2 ). Moreover, the optimized PeLED exhibits a 15.8‐fold increase in operational lifetime (from 15.5 to 245.7 min at 100 cd m −2 ) and markedly reduced current hysteresis, attributed to suppressed ion migration and stabilized interfacial energetics. This work highlights an effective pathway toward realizing vacuum‐processed, high‐performance perovskite emitters through rational multi‐functional interface design.