Dual-Ligand Synergistic\nPassivation Strategy for High-Brightness\nPerovskite Quantum Dot Light-Emitting Diodes

Although high-efficiency perovskite\nquantum dots (PQDs)-based\nlight-emitting\ndiodes (PQLEDs) have been achieved, their brightness is still limited\ndue to halogen element loss and surface ligand mismatch in PQDs. Here,\nto passivate surface vacancies and defects of CsPbBr<sub>3</sub>-based\nPQDs, we proposed a dual-ligand synergistic passivation (DSP) strategy,\nin which the alkaline metal ion Na<sup>+</sup> was employed to couple\nwith halogen ions, and the long-chain ligand oleic acid was utilized\nfor in situ ligand compensation. By using this DSP strategy, the bromine\nvacancies (V<sub>Br</sub>) and defects on the surface of CsPbBr<sub>3</sub>-based PQDs were successfully passivated, leading to the PQDs\nshowing a higher photoluminescence quantum yield, faster radiative\nrecombination rate, and longer exciton lifetime than the unpassivated\nones. As a result, the obtained CsPbBr<sub>3</sub>-based PQLEDs exhibited\nan impressive brightness of 160,900 cd m<sup>–2</sup>, which\nwas 2.89 times higher than those of the unpassivated devices. To the\nbest of our knowledge, this is the highest brightness ever reported\nfor the PQLEDs. We believe that the demonstrated high-brightness PQLEDs\nmay open a path for the design of higher-brightness PQLEDs.