High‐Efficiency Blue Perovskite Light‐Emitting Diodes with Improved Photoluminescence Quantum Yield via Reducing Trap‐Induced Recombination and Exciton–Exciton Annihilation

Abstract Although the performance of blue perovskite LEDs (PeLEDs) has improved rapidly in the past few years, it still lags behind their green and red counterparts. One major cause of the inferior performance is the relatively low photoluminescence quantum yield (PLQY) of blue perovskite emitters due to more severe nonradiative recombination loss induced by traps and exciton–exciton annihilation (EEA). In this study, theoretical analysis reveals that trap‐induced recombination limits the maximum obtainable PLQY and EEA leads to fast roll‐off at high excitons densities. To address these issues, a synergic approach by introducing CsAc into perovskite and applying solvent annealing (SA) is used to suppress the trap‐induced recombination and the EEA, respectively. The acetate anion in CsAc effectively passivates defects of perovskite through Lewis acid–base reaction, enhancing PLQY of the perovskite films from 10.7% to 49.2%. Furthermore, carrier recombination dynamic investigations reveal that EEA and PLQY roll‐off are successfully deferred with SA treatment. As a result, external quantum efficiency (EQE) is improved from 2.9% to 11% and EQE roll‐off is significantly suppressed at high current density. This work demonstrates that alleviating trap‐induced and EEA non‐radiative losses are two effective methods to improve the PLQY and EQE of blue PeLEDs.