Multisite Cross-Linked Ligand Suppressing Ion Migration for Efficient and Stable CsPbBr3 Perovskite Quantum Dot-Based Light-Emitting Diodes

Perovskite quantum dots (QDs), as promisingly solution-processed emitters, have produced impressive external quantum efficiencies (EQEs) in light-emitting diodes (LEDs). However, the operational stability of perovskite QD-based LEDs (QLEDs) is still limited by severe ion migration. Here, we propose a multisite cross-linked ligand strategy using alpha-lipoic acid (LA) molecules to simultaneously reduce non-radiative recombination and suppress ion migration in QLEDs. Meanwhile, the introduction of cross-linked LA ligands can reduce the roughness and contact potential difference variation of QD films, which facilitates the injection and recombination of carriers in devices. As a result, the colour-saturated green CsPbBr3-based QLED deliver a maximum EQE of 25.6 % together with an operational lifetime of 1340 h at an initial luminance of 100 cd m-2, representing the most efficient and stable perovskite LEDs based on cross-linked QDs. The improvement in device stability is attributed to the reduced ion migration, which is confirmed by analyzing the current behavior of QLEDs and time-of-flight secondary-ion mass spectrometry. This study provides a facile strategy for mitigating halide ion migration in perovskite fields toward more efficient and stable perovskite QLEDs.