Exciton-Polaron in a quasi-one-dimensional chain of hexyl-diammonium-BiI5 octahedra

Lower dimensional hybrid perovskite exhibits intriguing similarities to traditional quantum confined inorganic semiconductors with comparable exciton binding energies. The presence of flexible organic cations acting as spacers and stabilizers enhances electron-phonon couplings, further amplifying the potential for modular light-matter interactions in these materials. One-dimensional analogs of perovskite remain largely unexplored in the literature, representing a promising frontier for optoelectronic investigations. Herein we unravel the nature of excitons in a class of quasi-1D chain of corner-sharing Bismuth Iodide octahedral that mimics the low-dimensional hybrid organic-inorganic perovskite materials. Using broadband femtosecond impulsive Raman spectroscopy and detailed electronic structure calculations, we quantify the exciton lifetime and electron-phonon coupling constants to fully describe the excitation as an exciton-polaron. Our findings shed light on the immense potential of one-dimensional analogs of perovskites in developing novel materials with enhanced optoelectronic properties amenable to light conversion technologies.