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Title: Cross-plane coherent acoustic phonons in two-dimensional organic-inorganic hybrid perovskites

Two-dimensional, Ruddlesden-Popper organic-inorganic hybrid layered perovskites (2D-RPs) are solution-grown semiconductors with prospective applications in next-generation optoelectronics. The heat-carrying, low-energy acoustic vibrations of 2D-RPs, which are important for heat management of 2D-RP-based devices, have remained unexplored. Here we report on the propagation of coherent longitudinal acoustic phonons along the cross-plane direction of 2D-RPs, following separate characterizations of below-bandgap refractive index for each 2D-RP. Through experiments on crystals of systematically varied perovskite layer thickness, we demonstrate significant reduction in both group velocity and propagation length of acoustic phonons in 2D-RPs as compared to the three-dimensional methylammonium lead iodide. As borne out by a minimal coarse-grained model, these vibrational properties arise from a large acoustic impedance mismatch between the alternating layers of perovskite sheets and bulky organic cations. Furthermore, our results inform on thermal transport in highly impedance-mismatched crystal sub-lattices and provide insights towards design of materials that exhibit highly anisotropic thermal dissipation properties.
Authors:
 [1] ; ORCiD logo [2] ;  [2] ;  [1] ;  [2] ;  [1] ;  [2] ;  [3]
  1. Argonne National Lab. (ANL), Lemont, IL (United States)
  2. Northwestern Univ., Evanston, IL (United States)
  3. Argonne National Lab. (ANL), Lemont, IL (United States); Northwestern Univ., Evanston, IL (United States)
Publication Date:
Grant/Contract Number:
AC02-06CH11357
Type:
Accepted Manuscript
Journal Name:
Nature Communications
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 2041-1723
Publisher:
Nature Publishing Group
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE
OSTI Identifier:
1461512