Unveiling Sb Doping and Tricolor Luminescence from Intrinsic Self-Trapped Excitons in CsZnCl Crystals.

Zero-dimensional (0D) lead-free halide perovskites have lately received significant interest owing to their captivating broadband emissions. An in-depth understanding of the luminescence mechanism of self-trapped excitons (STEs) and realization of effective regulation of luminescence properties have become a major challenge in the research of lead-free metal halides. Herein, we have synthesized the CsZnCl and Sb-doped CsZnCl crystals and conducted a comprehensive investigation into their distinct electronic structures and optical characteristics. The findings from both experimental and theoretical investigations indicate that the tricolor luminescence in CsZnCl and blue emission in Sb-doped CsZnCl stem from intrinsic STEs, and the near-infrared emission originates from extrinsic STEs associated with the Sb ion in Sb-doped CsZnCl. Sb doping increases the quantum yield of CsZnCl to a large extent. In addition, intersystem crossing, exciton self-trapping, and lattice relaxation are the main reasons for the large Stokes shift. The present study is expected to provide a novel perspective for researchers in comprehending the luminescent mechanism of STEs and advancing the utilization of 0D lead-free metal halides in optoelectronic applications.