Synergistic Passivation Inducing Long‐Term Stability for Fluorescent CsPbI₃ Perovskite Nanocrystals

Abstract Cesium lead halide perovskite nanocrystals (PNCs) are promising candidates for photoelectric applications due to their remarkable optoelectronic properties. However, the poor stability of PNCs, especially oleic acid (OA)/oleylamine (OAm)‐capped CsPbI₃, is the main obstacle to their commercialization. In this study, CsPbI₃ PNCs with long‐term stability are prepared through synergistic passivation of n‐octylphosphonic acid (OPA) and (3‐aminopropyl) triethoxysilane (APS). OPA provides a stronger binding affinity to passivate surface defects, while the SiO₂ layer formed by APS can further reduce ligand detachment and block the access of external factors to the PNCs. The stability of OPA/APS‐capped CsPbI₃ PNCs can be synergistically enhanced in comparison with that of OA/OAm‐capped PNCs, the fluorescence of which can be also increased significantly. Employing the high‐performance OPA/APS‐capped CsPbI₃ PNCs as color‐converting materials, a white light‐emitting diode with a color coordinate of (0.33 and 0.32) and a wide color gamut of 126% National Television Standard Committee color space is fabricated.