Targeted Distribution of Passivator for Polycrystalline Perovskite Light-Emitting Diodes with High Efficiency

Although a variety of passivators have been researched to passivate the defects, sufficient defect passivation still remains a challenge to further elevate the efficiency of perovskite light emitting diodes (PeLEDs). Herein, we report that the BMIM+ ions of the 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) ionic liquid have effective passivation interaction to the Pb-related defects. And, the spontaneously formed targeted distribution of the BMIM+ ions on the crystal surface and film top surface of the polycrystalline perovskite layers well matches the defect site distribution, resulting in the defects being sufficiently passivated. As a result, sufficient defect passivation of ionic liquid enables the photoluminescence quantum yields (PLQYs) to reach 100% and the maximum external quantum efficiency (EQE) of the PeLEDs increased to 22.9%. This work initializes the selection of the promising ionic liquid passivators for high efficiency PeLEDs and highlights the critical role of the passivator spatial distribution for sufficient defect passivation.