Stable and Intense Violet-Emitting CsPbCl₃ Nanocrystals for Light-Emitting Diodes: Directly Obtained by L-Type Surface Passivation

Poor photoluminescence quantum yield (PLQY) and stability of the violet-emitting CsPbCl 3 NCs are responsible for the very low efficiency of the violet LEDs (<435 nm) based on these substances. Herein, we report a direct method of obtaining CsPbCl 3 NCs with exceptional characteristics employing diphenylphosphoryl chloride, which serves not only as an efficient chloride precursor but also prevents protonation of the amine ligand. High PLQY (∼87%) and remarkable stability of these NCs in a polar environment, at high temperature, and with low-density capping ligands are attributed to the strong L-type coordination of the unprotonated amine ligand with Pb 2+ of a PbCl x -terminated surface. A high-performance violet LED with an ultrapure PL at 410 nm, a narrow bandwidth of 12 nm, and an external quantum efficiency of ∼0.16 to 0.19% is achieved using these NCs as emitting materials. The results not only provide an alternative approach to obtaining quality CsPbCl 3 NCs but also highlight their potential in optoelectronic applications (like in LEDs, lasers, photodetectors) in this challenging high-energy spectral region.