Nature and Role of Structural Disorder in Low-Dimensional Hybrid Post-perovskite Phosphors

Low-dimensional hybrid lead halide post-perovskites based on trans-2,5-dimethylpiperazinium cations have drawn attention owing to their enhanced white-light emission compared to that of hybrid perovskites. For this family of materials, the quantum yield of the white photoluminescence is reported to be up to 5-fold of the record for hybrid perovskites. However, the crystal structures remain poorly described because of the important intrinsic disorder. Especially, the organic cations, which are thought to be key in preventing the thermal quenching of photoluminescence with temperature, could not be localized. In this article, new isostructural tin halide one-dimensional (1D) postperovskites are synthesized, and their crystal structures are analyzed. The disorder of organic molecules is further investigated through X-ray diffraction (XRD), solid-state NMR experiments, and FT-Raman spectroscopy on a large series of low-dimensional hybrid post-perovskites.