Manipulating Ion‐Dipole Interaction in CsPbBr 3 Quantum Dots for Efficient and Stable Perovskite Light‐Emitting Diodes

Abstract Perovskite quantum dots (PQDs) show significant application potential in next‐generation lighting and displays due to the favorable optoelectrical features and good solution processability. However, the ionic nature with high surface energy and metastable structure of PQDs limits the stability. Here a facile approach is reported for realizing stable CsPbBr 3 PQDs based on ion‐dipole interaction, in which ammonium bromide is used as a bromine source to achieve the regulation of PQDs precursor and tri(o‐tolyl) phosphine is utilized as a short‐chain ligand to modulate the ligand composition on the surface of PQDs. By the synergistic effect of precursor and long/short‐chain ligands, bright CsPbBr 3 PQDs are synthesized with a near‐unity photoluminescence quantum yield and long TRPL lifetime of 285.98 ns. More importantly, the CsPbBr 3 PQDs show excellent long‐term stability toward water, light, and heat, in which the initial fluorescence intensity can remain 80% after dispersion in water for 7 days and 82% underhigh‐temperature treatment at 433K. Further, highly efficient perovskite electroluminescent light‐emitting diodes (PeLEDs) are constructed with a maximum external quantum efficiency (EQE max ) of 25.88%. This established strategy achieves the EQE max record for PeLEDs prepared from bulk‐modified CsPbBr 3 PQDs, and breaks the barrier between simultaneously improving material stability and device efficiency, providing a powerful platform for the future development of high‐quality PQDs with significant applications.