Mitigating Ligand Entanglement in Perovskite Quantum Dots for High‐Efficiency and Stable Red Light‐Emitting Diodes

ABSTRACT Achieving simultaneously high efficiency and thermal stability in perovskite quantum dot light‐emitting diodes (PeLEDs) requires fundamentally rethinking surface ligand design. Conventional OAm‐OA ligands inadequately passivate halide vacancies, causing defect‐induced exciton quenching and low efficiency. Beyond this limitation, we reveal for the first time that thermal field triggers ligand entanglement at the atomic scale, which destabilizes the N─H passivation network, induces ligand desorption, and causes rapid stability degradation. This previously unrecognized failure mechanism underscores the need for thermally stable ligand architectures. Herein, we developed a novel stabilization strategy using PFBA ligands that can simultaneously enhance the efficiency and thermal stability of CsPbI ₃ QDs. Specifically, PFBA effectively passivates I vacancies and suppresses LO phonon‐exciton coupling to enhance the radiative recombination efficiency. Simultaneously, PFBA ligands with rigid fluorinated architectures effectively mitigate thermally induced ligand entanglement, while significantly enhancing OAm‐QD binding energy from −1.15 to −3.54 eV through charge‐sharing interactions. This approach yields CsPbI ₃ QDs exhibiting a 93% PLQY, a 27.1% peak EQE, and 22.8 h of T ₅₀ , representing 1.3, 1.8, and 16.3‐fold improvements over controls, respectively. This study establishes simultaneous suppression of defect‐mediated exciton loss and ligand entanglement as a unified design principle for high‐efficiency and stable PeLEDs.