Multidentate Ligand Polyethylenimine Enables Bright Color-Saturated Blue Light-Emitting Diodes Based on CsPbBr₃Nanoplatelets

Solid-state color-saturated blue emitters are an essential part of light-emitting diodes (LEDs) and high-definition displays, and lead halide perovskite nanomaterials are one such type of emitter. Using a multidentate ligand polyethylenimine (PEI), we developed a soft template method to stabilize and enhance solid-state blue photoluminescence of CsPbBr₃ nanoplatelets, whose lateral size became significantly increased without changing the thickness. From the spectral analysis, the PEI soft template prevented the coalescence of the CsPbBr3 nanoplatelets and decreased the density of their trap states, leading to a high photoluminescence quantum yield of 85% for their color-saturated blue emission in solution and 40% in films. LEDs based on CsPbBr3 nanoplatelets emit blue light at 465 nm with a high brightness of 631 cd m^-2.