Pressure-Driven Emission Enhancement in Zero-Dimensional [TPPen]₂SbBr₅ through the Lone Pair-π Interaction

Low-dimensional hybrid metal halides (LDMHs) exhibit markedly distinctive optoelectronic properties due to their unique quantum effects and strong exciton binding energies. Given the pressing need to accelerate research on the design of optoelectronic materials and their device integration, it is imperative to investigate the correlation between the structural properties of LDMHs and the underlying photophysical mechanisms responsible for their unique luminescent characteristics. In this work, we realize a 40-fold pressure-induced photoluminescence (PL) emission increase in the zero-dimensional (0D) compound [TPPen]₂SbBr₅ (TPPen = triphenylpentylphosphonium) and more notably the PL intensity is further enhanced upon pressure released. In situ characterizations and theoretical calculations indicate that pressure promotes lone pair-π (LP-π) interactions between Sb³⁺ lone-pair electrons and the π-electrons of the phenyl rings, thereby enabling more efficient charge transfer (CT) across the organic-inorganic interface, leading to significantly enhanced PL intensity. The irreversible structural distortion and lattice disruption caused the reservation of pressure-induced emission enhancement. This study offers a new strategy for facilitating CT between organic ligands and inorganic polyhedra and provides new perspectives into pressure-induced emission phenomena in 0D hybrid metal halides.