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 CsPbCl3 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 CsPbCl3 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 Pb2+ of a PbClx-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 CsPbCl3 NCs but also highlight their potential in optoelectronic applications (like in LEDs, lasers, photodetectors) in this challenging high-energy spectral region.