Optical polarization properties of TPP₂MnBr₄ perovskite crystal adjusted by the self-trapping state

Low-dimensional networked organic-inorganic hybrid metal halide crystal has become an emerging hotspot material due to its opportunities and advantages in the development of white-light-emitting diodes. Therefore, its photoluminescence (PL) mechanism is important. Herein, we study the PL behavior of columniform TPP₂MnBr₄ crystals using multi-spectroscopy. The temperature-dependent PL data show that the PL of the TPP₂MnBr₄ crystal originates from the recombination of a self-trapping exciton. A polarization-dependent PL test suggests that the self-trapping exciton is anisotropic, which indicates that the distribution of self-trapping states is sensitive to the orientation of the crystal axis. Space-resolved PL spectroscopy shows that the anisotropy of PL gradually weakens along the orientation of the columniform crystal, which has a longer relaxation distance than traditional light-wave-guiding behavior. Thus, anisotropy of PL can exist before it disappears in the crystal. Our results elucidate the PL mechanism of low-dimensional networked organic-inorganic hybrid metal halide crystals and provide a foundation for advanced optical polarization devices based on them.