Narrow-Band Violet-Light-Emitting Diodes Based on Stable Cesium Lead Chloride Perovskite Nanocrystals

CsPbCl3 nanocrystals are potential ultrapure emitters. But it is challenging to synthesize CsPbCl3 nanocrystals with sufficient stability, which impedes their application in light-emitting devices. In this work, we report a facile phosphoryl-chemistry-mediated synthesis approach to synthesizing stable CsPbCl3 nanocrystals, in which the phenylphosphonic dichloride (PhPOCl2) precursor is employed. In addition to the high reactivity of the P–Cl bond of PhPOCl2 for providing adequate Cl, the derived P=O with good proton affinity facilitates the formation of a distinct nanocrystal surface with the nonprotonated oleylamine (OLA) ligand. Accordingly, the L-type-ligand-capped CsPbCl3 nanocrystals exhibited not only bright luminance but also good stability that endured repeated purification up to 10 cycles. Based on the stable CsPbCl3 nanocrystals, we achieved violet LEDs with extremely narrow electroluminescence spectra (full width at half-maximum ≈ 10.6 nm).