Dual ligand modification enabling bright and stable CsPbBr2.8Cl0.2 nanoplatelets in polar solvents†

Strong quantum-confined nanoplatelets (NPLs) have emerged as one of the most promising materials for achieving blue emission. However, due to the ionic properties of the perovskite lattice, it thermodynamically exhibits no resistance to polar environments. Herein, the stable mixed halide blue NPLs with lateral dimensions of 12.59 nm under the polar solvent ethyl acetate are achieved by dual ligand engineering. H⁺ released by HCl can be used to generate a more complete Pb–X and more protonated octylamine, thus etching imperfect nanocrystals with the help of HBr and ultimately regulating the growth of NPLs. Simultaneously, the anions isolated by DPH deamination can be tightly anchored to the lattice surfaces to saturate the defect sites and create a robust ligand shell, succeeding in a photoluminescence quantum yield (PLQY) of more than 90% from 465 nm to 495 nm. Therefore, the modified NPLs can be stably stored in ethyl acetate for 15 days with little decrease in fluorescence intensity and exhibit increased stability when exposed to ultraviolet radiation. This work offers novel perspectives on the production of mixed halide blue NPLs that are bright and stable in polar solvents.