Multisite Coordination Ligand Strategy for FAPbBr3 Nanocrystal Light-Emitting Diodes

Abstract

Passivation strategies have been proven to improve the optoelectronic properties of perovskite nanocrystals (PNCs) and to suppress their ion migration; however, previous studies have predominantly focused on their binding affinity to uncoordinated Pb2+ ions, overlooking additional interactions with monovalent cations. Here, we introduce multisite coordination ligands (composed of multiple fluorine atoms) to achieve additional interactions with formamidinium lead bromide (FAPbBr3) PNCs. One fluorine atom passivates an uncoordinated Pb2+ ion, while the other fluorine atoms form hydrogen bonds with the surrounding FA+ ions, thereby strongly binding to the PNC surface and suppressing ion migration. This strong passivation enables postsynthetic ligand exchange using polar solvents without compromising the optoelectronic properties of PNCs by protecting them from polar solvents. As a result, we achieve efficient PNC-LEDs with a maximum external quantum efficiency (EQE) of 25.2% at a luminance of 4474 cd m-2, maintaining an EQE of over 20% up to approximately 8000 cd m-2.