Hot Carrier Dynamics in Bulk and 2D Perovskites*

A comparison of the effect of carrier-carrier and carrier-phonon interactions in 2D (BA)₂PbI₄ Ruddlesden-Popper (n=1) and conventional bulk MAPbI₃ perovskite thin films is presented. It is shown that the nature and strength of the exciton binding energy strongly mediate the nature of their interaction with phonons. Specifically, more strongly coupled excitons manifest themselves in the formation of small polarons that interact with lattice via the emission of LO-phonon replicas, while weakly bound (or free) excitons interact with phonons to form large polarons resulting in large LO-phonon broadening and strong carrier-phonon scattering. These results suggest that the unusual hot carrier thermalization observed in the perovskites is dominated by the strength and nature of the exciton-phonon interaction and subtlety different from more conventional semiconductors. To support this hypothesis, comparisons of the hot carrier dynamics and electron-phonon interaction in a number of stable and well-studied perovskites are also presented.