Bright Blue Emission Lead-Free Halides with Narrow Bandwidth Enabled by Oversaturated Europium Doping.

Eu-based lead-free metal halide nanocrystals (LFMH NCs), including CsEuCl NCs and CsX:Eu NCs (X = Cl or Br), exhibit highly efficient narrow-band blue photoluminescence, making them competitive candidates for next-generation lighting and displays. However, the growing mechanism of the aforementioned NCs lacks in-depth study, which hinders the development of Eu-based nanomaterials. Herein, we demonstrate the colloidal synthesis of CsBr:Eu NCs based on an air-stable europium source.