Polaronic quantum confinement in bulk CsPbBr3 perovskite crystals revealed by state-resolved pump/probe spectroscopy

Abstract

Disorder is intrinsic to weakly bound ionic systems and gives rise to specific electronic processes. In recently developed perovskite ionic crystals, this dynamic lattice disorder is inferred to give rise to properties of interest, such as defect tolerance. Here, the elementary excitation of interest is the polaron, a localized lattice distortion. We employ state-resolved pump/probe spectroscopy to monitor electron and lattice dynamics in bulk CsPbBr3 perovskite crystals. The data report surprising line-shape dynamics. Rather than causing redshifting of the band edge exciton, polaron formation gives rise to confinement induced dynamical processes leading to a blueshift in the band edge bleach feature. In these ionic nanocrystals, the formation of quantum confined excitons arises from the polaronic potential, as opposed to physical confinement in conventional covalent quantum dots, resulting in an excitation of a quantum confined exciton polaron. This state may represent an alternative quasiparticle.