Regulating Surface-Passivator Binding Priority for Efficient Perovskite Light-Emitting Diodes

Suppressing trap-assisted nonradiative losses through passivators is a prerequisite for efficient perovskite light-emitting diodes (PeLEDs). However, the complex bonding between passivators and perovskites severely suppresses the passivation process, which still lacks comprehensive understanding. Herein, the number, category, and degree of bonds between different functional groups and the perovskite are quantitatively assessed to study the passivation dynamics. Functional groups with high electrostatic potential and large steric hindrance prioritize strong bonding with organic cations and halides on the perfect surface, leading to suppressed coordination with bulky defects. By modulating the binding priorities and coordination capacity, hindrance from the intense interaction with perfect perovskite is significantly reduced, leading to a more direct passivation process. Consequently, the near-infrared PeLED without external light out-coupling demonstrates a record external quantum efficiency of 24.3% at a current density of 42 mA cm^-2. In addition, the device exhibits a record-level-cycle ON/OFF switching of 20 000 and ultralong half-lifetime of 1126.3 h under 5 mA cm^-2. An in-depth understanding of the passivators can offer new insights into the development of high-performance PeLEDs.