Self-Trapped Exciton Emission in a Zero-Dimensional (TMA)₂SbCl₅·DMF Single Crystal and Molecular Dynamics Simulation of Structural Stability

Lead-free lower-dimensional organic–inorganic metal halide materials have recently triggered intense research because of their excellent photophysical properties and chemical stability. Herein, we report a novel zero-dimensional (0D) organic–inorganic hybrid single crystal (TMA)2SbCl5·DMF (TMA = N­(CH3)3, DMF= HCON­(CH3)2), which exhibits typical self-trapped exciton (STE) emission with an efficient yellow emission at 630 nm and high photoluminescence quantum yield (PLQY) of 67.2%. The dual STE emission is attributed to the singlet and triplet STEs in inorganic [SbCl5]2–, respectively. Further, an ab initio molecular dynamics simulation was performed to estimate the stability of crystal structure at room temperature. The calculated excited-state structure indicates that the deformation parameter (Δd) of the excited-state structure is larger than that of the ground state, illustrating the origin of a large Stokes shift. These results indicate that these new 0D lead-free organic–inorganic hybrid metal halides are promising luminescent materials for optoelectronic applications.