Stable Broadband Bright Green Emission of Self‐trapped Excitons Triggered by Sb3+ Doping in Zero‐Dimensional Cs3BiCl6

Abstract Low‐dimensional lead‐based metal halide perovskites (MHPs) have many exceptional photoelectric capabilities thanks to the 6 s 2 electron structure of lead ion (Pb 2+ ). Pb 2+ ′s toxicity, however, has prevented its widespread development and use. Finding ions in the valence layer that have a comparable electrical structure thus makes sense as Pb 2+ replacements. In this work, all inorganic zero‐dimensional (0D) Cs 3 BiCl 6 single crystal was synthesized by the anti‐solvent crystallization method. There is no obvious photoluminescence (PL) phenomenon for Cs 3 BiCl 6 at room temperature (RT). It is found that the extremely strong exciton‐phonon interaction leads to seriously non‐radiative recombination. After doping with Sb 3+ , Cs 3 BiCl 6 : Sb achieved broadband emission with a significant Stokes shift, the photoluminescence quantum yield (PLQY) up to 15.85 %, which has a microsecond PL decay lifetime and excellent environmental stability. Systematic spectroscopic characterizations unveil the PL mechanism of Cs 3 BiCl 6 : Sb is self‐trapped excitons (STEs) emission, and theoretical calculation revealed the indirect bandgap properties of Cs 3 BiCl 6 and Cs 3 BiCl 6 : Sb.