Multicolor ultralong phosphorescence from perovskite-like octahedral α-AlF.

Designing organic fluorescent and phosphorescent materials based on various core fluorophore has gained great attention, but it is unclear whether similar luminescent units exist for inorganic materials. Inspired by the BX octahedral structure of luminescent metal halide perovskites (MHP), here we propose that the BX octahedron may be a core structure for luminescent inorganic materials. In this regard, excitation-dependent color-tunable phosphorescence is discovered from α-AlF featuring AlF octahedron. Through further exploration of the BX unit by altering the dimension and changing the center metal (B) and ligand (X), luminescence from KAlF, (NH)AlF, AlCl, Al(OH), GaO, InCl, and CdCl are also discovered. The phosphorescence of α-AlF can be ascribed to clusterization-triggered emission, i.e., weak through space interaction of the n electrons of F atoms bring close proximity in the AlF octahedra (inter/intra). These discoveries will deepen the understanding and contribute to further development of BX octahedron-based luminescent materials.