Acoustic phonon instabilities and central peaks at the Brillouin zone boundary in the organic-inorganic perovskite CH<sub>3</sub>NH<sub>3</sub>PbCl<sub>3</sub>

ORAL

Abstract

Lead halide hybrid perovskites consist of an inorganic framework hosting a molecular cation located in the interstitial space. These compounds have been extensively studied as they have been identified as promising materials for photovoltaic applications. In particular, the interaction between the molecular cation and the inorganic framework has been suggested to influence the electronic properties. CH3NH3PbCl3 undergoes several structural transitions associated with both distortion of the octahedra and orientational ordering of the CH3NH3 cation. We have measured the low-frequency lattice dynamics using neutron spectroscopy. We report an anomaly in the acoustic phonon linewidth towards the high-symmetry point QX= (2, 1/2, 0) when approaching the transitions, and a hardening of the entire phonon branch with decreasing temperature. Measurements at the Brillouin zone edges QX= (2, 1/2, 0), QM= (3/2, 1/2, 0) and QR= (3/2, 3/2, 5/2) show central peaks appearing at the lower temperature transition. We discuss the presence of both central peaks and acoustic phonon instabilities as evidence of a strong coupling between the inorganic framework and the molecular cation.

*We acknowledge funding from the EPSRC and the STFC

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Presenters

  • Manila Songvilay

    • University of Edinburgh
    • Physics, University of Edinburgh

Authors

  • Manila Songvilay

    • University of Edinburgh
    • Physics, University of Edinburgh

  • Maryam Bari

    • Department of Chemistry and 4D labs, Simon Fraser University

  • Ye Zuo-Guang

    • Department of Chemistry and 4D labs, Simon Fraser University
    • Simon Fraser University

  • Guangyong Xu

    • NIST Center for Neutron Research, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • NCNR, NIST
    • NIST Center for Neutron Research

  • Peter M Gehring

    • NIST Center for Neutron Research, National Institute of Standards and Technology
    • NCNR, NIST
    • National Institute of Standards and Technology

  • William Ratcliff

    • NIST Center for Neutron Research, National Institute of Standards and Technology
    • National Institute of Standards and Technology
    • NIST Center for neutron research, National Institute of Standard and Technology, Gaithersburg, MD
    • NIST

  • Karin Schmalzl

    • Forschungszentrum Jülich GmbH, Jülich Centre for Neutron Science at ILL

  • Frédéric Bourdarot

    • INAC, MEM/MDN, Université Grenoble Alpes, CEA

  • Bertand Roessli

    • Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institut (PSI)

  • Chris Stock

    • University of Edinburgh
    • Physics, University of Edinburgh
    • U. Edingburgh
    • Univ of Edinburgh