• Rapid Communication

From soft harmonic phonons to fast relaxational dynamics in CH3NH3PbBr3

I. P. Swainson, C. Stock, S. F. Parker, L. Van Eijck, M. Russina, and J. W. Taylor
Phys. Rev. B 92, 100303(R) – Published 8 September 2015
PDFHTMLExport Citation

Abstract

The lead-halide perovskites, including CH3NH3PbBr3, are components in cost effective, highly efficient photovoltaics, where the interactions of the molecular cations with the inorganic framework are suggested to influence the electronic and ferroelectric properties. CH3NH3PbBr3 undergoes a series of structural transitions associated with orientational order of the CH3NH3 (methylammonium) molecular cation and tilting of the PbBr3 host framework. We apply high-resolution neutron scattering to study the soft harmonic phonons associated with these transitions, and find a strong coupling between the PbBr3 framework and the quasistatic CH3NH3 dynamics at low energy transfers. At higher energy transfers, we observe a PbBr6 octahedra soft mode driving a transition at 150 K from bound molecular excitations at low temperatures to relatively fast relaxational excitations that extend up to 50100 meV. We suggest that these temporally overdamped dynamics enables possible indirect band gap processes in these materials that are related to the enhanced photovoltaic properties.

  • Figure
  • Figure
  • Figure
  • Figure
  • Received 10 May 2015

DOI:https://doi.org/10.1103/PhysRevB.92.100303

©2015 American Physical Society

Authors & Affiliations

I. P. Swainson1, C. Stock2, S. F. Parker3, L. Van Eijck4,5, M. Russina6, and J. W. Taylor3,7

  • 1National Research Council, Chalk River, Ontario, Canada KOJ 1JO
  • 2School of Physics and Astronomy, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom
  • 3ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, United Kingdom
  • 4Institut Laue-Langevin, 6 rue Jules Horowitz, Boîte Postale 156, 38042 Grenoble Cedex 9, France
  • 5Reactor Institute Delft, Delft University of Technology, 2629JB Delft, Netherlands
  • 6Helmholtz Zentrum Berlin für Materialien und Energie GmbH, D-14109 Berlin, Germany
  • 7European Spallation Source, Universitetparken 1, 2100, Copenhagen, Denmark

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand
Issue

Vol. 92, Iss. 10 — 1 September 2015

Reuse & Permissions
Access Options
Author publication services for translation and copyediting assistance advertisement

Authorization Required


×
×

Images

×

Sign up to receive regular email alerts from Physical Review B

Log In

Cancel
×

Search


Article Lookup

Paste a citation or DOI

Enter a citation
×