LAUSR

Metal halide luminescent materials, particularly those doped with ns2 ions, exhibit exceptional optical properties. However, the luminescent mechanisms associated with the stereochemical activity of lone-pair electrons remain insufficiently explored. In this study, zero-dimensional (0D) tin-based halide (C4H12N)2SnCl6 is utilized as a model system to investigate the effects of lattice distortion and lone-pair electron expression on fluorescence emission characteristics by doping with 6s2 and 5s2 ions. The findings reveal that compared to 6s2 ions, 5s2 ion doping results in stronger electron-phonon coupling, causing significant octahedral lattice distortion and producing unique dual emissions along with a large Stokes shift of 317 nm. Remarkably, even at temperatures as high as 360 K, (C4H12N)2SnCl6:Sb maintains its dual emission due to insufficient thermal activation energy to promote electron transition from excited state 1 to excited state 2. In contrast, 6s2 doping exhibits a single blue emission with a small Stokes shift of 101 nm. Additionally, calculations of the electron localization function reveal that 5s2 lone pairs exhibit static stereochemical expression with specific spatial orientation, while 6s2 lone pairs display dynamic behavior. These findings highlight the critical role of lone-pair stereochemistry in governing the photophysical properties of ns2-doped metal halides, offering new insights into their luminescent mechanisms.