Dual lattice incommensurabilities and enhanced lattice perfection by low-temperature thermal annealing in photoelectric (CH3NH3)PbBr3

Wen-Hsien Li, Chi-Hung Lee, Tsu-Yin Ling, Ma-Hsuan Ma, Pai-Chun Wei, Jr-Hau He, Chun-Min Wu, Jen-Chih Peng, Guangyong Xu, Yang Zhao, and Jeffrey W. Lynn
Phys. Rev. Materials 5, 025401 – Published 1 February 2021

Abstract

The coupling between the organic CH3NH3+ cations and inorganic perovskite PbBr3 framework in a large single crystal of (CH3NH3)PbBr3 weighing 13 g was studied using neutron diffraction and inelastic neutron scattering. Two lattice incommensurate (ICM) phases were found; one at higher temperatures, marked ICMHT, appeared between 150 and 134 K. The second one, marked ICMLT, developed below 143 K and remained at 75 K. The transition from the ICMLT to ICMHT phase upon warming gave rise to extremely large lattice shrinking, followed by extremely large lattice expansion of the tetragonal basal plane of the PbBr3 lattice. There was a progressive decrease in the width of the diffuse peak at the Bragg position from the PbBr3 lattice upon warming, which can be described using a critical exponent to show complete ordering of the atoms into a (CH3NH3)PbBr3 lattice at 200 K. (CH3NH3)PbBr3 exhibits six definitive acousticlike phonon branches at 75 K. The six branches reconstruct into two at 200 K, with the frequencies of both the transverse and longitudinal modes greatly enhanced. The asymmetric structure of the CH3NH3 ions together with the indirect interactions between the CH3NH3 ions mediated through the Br ions are used to understand the observed behaviors.

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  • Received 7 October 2020
  • Revised 22 December 2020
  • Accepted 19 January 2021

DOI:https://doi.org/10.1103/PhysRevMaterials.5.025401

©2021 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Wen-Hsien Li1,*, Chi-Hung Lee1, Tsu-Yin Ling1, Ma-Hsuan Ma1, Pai-Chun Wei2, Jr-Hau He2,3, Chun-Min Wu4, Jen-Chih Peng4, Guangyong Xu5, Yang Zhao5,6, and Jeffrey W. Lynn5

  • 1Department of Physics, National Central University, Jhongli 32001, Taiwan
  • 2Computer, Electrical and Mathematical Sciences and Engineering Division, King Abdullah University of Science & Technology, Thuwal 23955, Saudi Arabia
  • 3Department of Materials Science and Engineering, City University of Hong Kong, Kowloon, Hong Kong SAR
  • 4National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan
  • 5NIST Center for Neutron Research, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
  • 6Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA

  • *whli@phy.ncu.edu.tw

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Vol. 5, Iss. 2 — February 2021

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