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

Low-dimensional lead-based metal halide perovskites (MHPs) have many exceptional photoelectric capabilities thanks to the 6 s(2) electron structure of lead ion (Pb2+). Pb2+'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 Pb2+ replacements. In this work, all inorganic zero-dimensional (0D) Cs3BiCl6 single crystal was synthesized by the anti-solvent crystallization method. There is no obvious photoluminescence (PL) phenomenon for Cs3BiCl6 at room temperature (RT). It is found that the extremely strong exciton-phonon interaction leads to seriously non-radiative recombination. After doping with Sb3+, Cs3BiCl6: 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 Cs3BiCl6: Sb is self-trapped excitons (STEs) emission, and theoretical calculation revealed the indirect bandgap properties of Cs3BiCl6 and Cs3BiCl6: Sb.