Strong electron-phonon interaction in 2D halide perovskite

Halide perovskites have provided a promising platform for optoelectronics in recent years. In the 2D halide perovskite, quantum confinement boosts the excitonic effect that facilitates emission process and dielectric confinement from surrounding molecules strongly modifies exciton energy. These confinements confer substantial versatility in the design and fabrication of next-generation optoelectronic devices. Here, we investigate the electron-phonon coupling by low temperature Raman spectroscopy, where a series of well resolved optical phonon modes are observed and assigned to octahedral cage twisting and bond vibrations, and some low energy modes can be contributed to anharmonic polar fluctuations. The optical modes are also confirmed by transient transmission measurement. Notably our result shows some new optical phonon modes which indicate the complexity and low symmetry of crystal. These results reveal the microscopic lattice dynamics that mediate exciton–phonon interaction and provide new insights into how lattice anharmonicity and polar phonons influence carrier dynamics in layered halide perovskites.