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 α‐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.