Activation Energy of Organic Cation Rotation in CH3NH3PbI3 and CD3NH3PbI3: Quasi-Elastic Neutron Scattering Measurements and First-Principles Analysis Including Nuclear Quantum Effects

Research output: Contribution to journalArticleScientificpeer-review

Researchers

  • Jingrui Li
  • Mathilde Bouchard
  • Peter Reiss
  • Dmitry Aldakov
  • Stéphanie Pouget
  • Renaud Demadrille
  • Cyril Aumaitre
  • Bernhard Frick
  • David Djurado
  • Mariana Rossi
  • Patrick Rinke

Research units

  • CNRS/IN2P3
  • Institut Laue-Langevin
  • Fritz-Haber-Institut der Max-Planck-Gesellschaft

Abstract

The motion of CH3NH3+ cations in the low-temperature phase of the promising photovoltaic material methylammonium lead triiodide (CH3NH3PbI3) is investigated experimentally as well as theoretically, with a particular focus on the activation energy. Inelastic and quasi-elastic neutron scattering measurements reveal an activation energy of ∼48 meV. Through a combination of experiments and first-principles calculations, we attribute this activation energy to the relative rotation of CH3 against an NH3 group that stays bound to the inorganic cage. The inclusion of nuclear quantum effects through path integral molecular dynamics gives an activation energy of ∼42 meV, in good agreement with the neutron scattering experiments. For deuterated samples (CD3NH3PbI3), both theory and experiment observe a higher activation energy for the rotation of CD3 against NH3, which results from the smaller nuclear quantum effects in CD3. The rotation of the NH3 group, which is bound to the inorganic cage via strong hydrogen bonding, is unlikely to occur at low temperatures due to its high energy barrier of ∼120 meV.

Details

Original languageEnglish
Pages (from-to)3969-3977
Number of pages9
JournalJournal of Physical Chemistry Letters
Volume9
Issue number14
Publication statusPublished - 19 Jul 2018
MoE publication typeA1 Journal article-refereed

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