Hybrid metal halides attract significant attention in materials science, chemistry, and photonics due to their attractive structural, electronic, and optical properties. However, zero-dimensional (0D) hybrid indium halides are still in their infancy. We report the first isomeric 0D indium halide single crystals showing green and delayed yellow emissions. Single-crystal X-ray structures reveal that these emissions originate from crystals with the molecular formula (C10H22N2)4In4Br20, consisting of organic ligands, InBr6 octahedra, and InBr4 tetrahedra. While both crystals carry eight corner-sharing and two face-sharing InBr6 octahedra, the four face-sharing InBr4 tetrahedra in the green-emitting isomer and two inner InBr4 tetrahedra in the yellow-emitting isomer mark the crystal isomerism, leading to distinct optical properties. The green-emitting crystals exhibit short excitonic lifetimes, whereas the radiative recombination in the yellow-emitting crystals is delayed by several hundred nanoseconds and redshifted, indicating a self-trapped exciton behaviour with a large Huang-Rhys factor and high activation energy. The structural and optical properties of the isomeric single crystals offer insights into the importance of developing 0D metal halides with multi-colour and delayed emission for sensors, LEDs, and displays.
Zhou et al. (2026) studied this question.