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Title: Lattice dynamics and the nature of structural transitions in organolead halide perovskites

Organolead halide perovskites are a family of hybrid organic-inorganic compounds whose remark- able optoelectronic properties have been under intensive scrutiny in recent years. Here we use inelastic X-ray scattering to study low-energy lattice excitations in single crystals of methylammonium lead iodide and bromide perovskites. Our ndings conrm the displacive nature of the cubic-to- tetragonal phase transition, which is further shown, using neutron and x-ray diraction, to be close to a tricritical point. The experimental sound speed, around 100-200 m/s, suggests that electron- phonon scattering is likely a limiting factor for further improvements in carrier mobility. Lastly, we detect quasistatic symmetry-breaking nanodomains persisting well into the high-temperature cubic phase, possibly stabilized by local defects. These ndings reveal key structural properties of these materials, but also bear important implications for carrier dynamics across an extended temperature range relevant for photovoltaic applications.
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [6] ;  [6] ;  [1] ;  [1] ;  [7] ;  [1]
  1. Univ. of Toronto, ON (Canada). Dept. of Electrical and Computer Engineering
  2. DuPont Central Research and Development, Wilmington, DE (United States); Univ. of Delaware, Newark, DE (United States). Dept. of Physics and Astronomy
  3. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  4. DuPont Electronics and Communication Technologies, Wilmington, DE (United States)
  5. DuPont Central Research and Development, Wilmington, DE (United States)
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical and Engineering Materials Division
  7. Carnegie Mellon Univ., Pittsburgh, PA (United States). Dept. of Mechanical Engineering
Publication Date:
OSTI Identifier:
Grant/Contract Number:
AC05-00OR22725; AC02-06CH11357
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 94; Journal Issue: 9; Journal ID: ISSN 2469-9950
American Physical Society (APS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source
Sponsoring Org:
Natural Sciences and Engineering Research Council of Canada (NSERC); USDOE Office of Science (SC)
Country of Publication:
United States