Bifunctional Electron‐Transport Layer Engineering Enables Energy‐Level Alignment and Interfacial Passivation for Efficient PeLEDs

ABSTRACT Perovskite light‐emitting diodes (PeLEDs) have been widely studied due to their excellent electroluminescence, high color purity, and adjustable size and composition. However, incomplete passivation of the light emitting layer (EML), unbalanced carrier injection, and numerous interface defects have also limited their further development. Herein, we propose an electron transport layer (ETL) modification strategy to address the critical issue in PeLEDs, where unbalanced charge injection and a high density of interface trap states hinder the simultaneous achievement of high efficiency and long operational lifespan. We deeply explored the influence of BPAH on the energy level and mobility of ETL, and revealed its strong interaction with EML. This interaction effectively passivated the surface defects of EML, promoted charge transport and radiative recombination. Ultimately, the BPAH treated PeLED achieved an external quantum efficiency of 23.9% and exhibited a remarkable 9.2‐fold enhancement in halftime, extending to 554 min.