Comprehensive Passivation for High‐Performance Quasi‐2D Perovskite LEDs

Quasi‐2D perovskites have demonstrated great application potential in light‐emitting diodes (LEDs). Defect passivation with chemicals plays a critical role to achieve high efficiency. However, there are still challenges in comprehensively passivating the defects distributed at surface, bulk, and buried interface of quasi‐2D perovskite emitting films, hindering the further improvement of device performance. Herein, 9,9‐substituted fluorene derivatives with different terminal functional groups are developed tactfully to realize comprehensive passivation, which greatly contributes to reducing nonradiative recombination at surface, suppressing ion migration in bulk, and filling interfacial charge traps at buried interface, respectively. Eventually, quasi‐2D perovskite LEDs have an increased external quantum efficiency from 18.2% to 23.2%, improved operation lifetime by more than six times and lower turn‐on voltage simultaneously. Here the importance of comprehensive passivation is highlighted and guidelines for the design and application of passivators for perovskite optoelectronics are provided. Defects in quasi‐2D perovskite films are comprehensively passivated by using developed series passivators with different solubility and passivation points. The defect‐induced surface nonradiative recombination, bulk ion migration, and buried interfacial charge trapping are resolved simultaneously. Quasi‐2D perovskite light‐emitting diodes with comprehensive passivation exhibit improved external quantum efficiency, extended operation lifetime, and reduced turn‐on voltage.