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.5 MoreReceived 25 November 2020Revised 26 February 2021Accepted 31 March 2021DOI:https://doi.org/10.1103/PhysRevResearch.3.023147Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasExcitonsOptoelectronicsPhononsPolaronsCondensed Matter, Materials & Applied Physics
Highlights
Semiconductor perovskites have remarkable optical properties that have generated much interest
We present pump/probe spectroscopy with sufficient time resolution to observe how polarons couple to excitons and control the manner in which excitons relax and recombine
Details of the fitting procedure and example fits can be found in the Appendix
Summary
Semiconductor perovskites have remarkable optical properties that have generated much interest. In contrast to CdSe, the response of ionically bound soft lattices, such as CsPbBr3 perovskite nanocrystals (NCs), was recently shown to have isomorphisms [16] with liquid phase solvation dynamics [25,26]. By monitoring the main bleach feature through time, it is possible to detect wave-packet motion along the excited state through modulations of the pump/probe signal
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