Coherent Exciton-Phonon Coupling In Perovskite Semiconductor Nanocrystals Studied By Two-Dimensional Electronic Spectroscopy

Perovskite semiconductor nanocrystals of lead halides exhibit excellent electronic and optical properties that are suitable for many optoelectronic applications. In this report, we investigate the underlying mechanism of the optical response of the material by probing coherent interaction between the exciton and lattice vibration by two-dimensional electronic spectroscopy. Coherent exciton-phonon coupling has been observed with time-domain oscillations in the dynamics of signals related to either ground or excited electronic states. Furthermore, the spectra of the coherent phonon derived from the dynamics of biexciton formation have larger amplitudes for higher frequency modes, which is attributed to the phonon bottleneck effect. Moreover, the composition-dependent coherent coupling between the exciton and lattice vibration in mixed halide samples reveals a critical role played by the anharmonicity and fluctuation of lattice vibration in the excited-state dynamics of perovskite nanocrystals.