Exciton-Phonon Coupling of Chiral One-Dimensional Lead-FreeHybrid Metal Halides at Room Temperature

The interaction between organic cations and inorganic metal halideoctahedral units strongly affects the properties of organic-inorganic hybrid metal halides.The"soft"property of the lattice provides the possibility of its strong exciton-phononinteraction. Here we report one-dimensional (1D) lead-free chiral organic-inorganic hybridmetal halide single crystals of (R/S)-methylbenzylamine bismuth iodide (R/S-MBA)2Bi2I8,which exhibits a high level of octahedral bond distortion. The introduction of chiral aminesleads to a strong chiroptical response in the range of 200-600 nm. The strong exciton-phonon coupling can be observed through the coherent oscillation spectrum of transientabsorption dynamics at room temperature. The coherent phonon oscillation frequencies are similar to 97 and similar to 130 cm-1, corresponding to the symmetrical stretching or bending of the Bi-Ioctahedron. Our work provides new insights for the study of exciton-phonon coupling in1D chiral hybrid metal halides.