High‐Brightness Blue Perovskite Light‐Emitting Diodes With Low Efficiency Roll‐Off Enabled by Dual‐ETL and Hole Transport Regulation

Abstract Metal halide‐based perovskite light‐emitting diodes (PeLEDs) have emerged as promising candidates for next‐generation commercial displays due to their high color purity and recent dramatic improvements in device efficiency. However, the performance of blue PeLEDs still falls far short of commercialization requirements, largely because achieving both high external quantum efficiency (EQE) and brightness simultaneously remains a significant challenge. Here, a facile synergistic regulation strategy is presented to address the charge balance issue by incorporating ethanolamine and ethanol as additives into the poly(3,4‐ethylenedioxythiophene) (styrene sulfonate) (PEDOT: PSS) hole transport layer (HTL), complemented by a dual electron transport layer (ETL) structure. The cosolvent‐assisted PEDOT: PSS enables systematic modulation of the hole injection/transport barrier and alleviates exciton quenching at the HTL/perovskite interface. Crucially, the introduction of 4,6‐bis(3,5‐di(pyridin‐3‐yl)phenyl)‐2‐methyl pyrimidine (B3PymPm) as part of the dual ETLs not only optimizes the energy level structure of the device but also enhances carrier balance and strengthens carrier confinement. As a consequence, the blue PeLED based on optimized charge‐carrier transport exhibits a reduced turn‐on voltage of 2.7 V, an unprecedented luminance of 2809 cd m ^{− 2} , a maximum EQE exceeding 7.6%, while maintaining an EQE of 7.2% at a high luminance of 2000 cd m ^{− 2} , and an extended operational lifetime.