In Situ Ligand Compensation of Perovskite Quantum Dots for Efficient Light-Emitting Diodes

Perovskite quantum dots (PQDs) have emerged as one of the most promising optoelectronic materials. However, oleic acid (OA)/oleylamine (OAm) ligands significantly suffer from detachment from the PQD surface due to the reversible protonated and deprotonated processes of OA and OAm ligands, predominantly affecting the optoelectronic properties of PQDs. Herein, an in situ ligand compensation (ILC) strategy is demonstrated to repair the defective surface of PQDs through a nucleophilic substitution reaction, which could simultaneously passivate the cesium and bromide ion vacancies on the PQD surface, substantially suppressing defect-assisted nonradiative recombination. Meanwhile, ILC treatment would also dynamically remove part of the pristine OA/OAm ligands, which improves the electronic coupling and crystalline orientation of PQDs, thereby facilitating charge transport within the PQD solids. Consequently, the PQD-based light-emitting diode yields an external quantum efficiency of up to 23.45% with the highest luminance of 109427 cd m –2, which is among the highest values of green-emitting PQD light-emitting diodes.