The mechanisms behind the exceptional photovoltaic properties of the metallorganic perovskites are still debated and include a ferroelectric (FE) state from the ordering of the electric dipoles of the organic molecules. We present the first anelastic (complex Young's modulus) and new dielectric measurements on CH3NH3PbI3, which provide new insight into the reorientation dynamics of the organic molecules and the reason why they do not form a FE state. The permittivity is fitted within the tetragonal phase with an expression that includes the coupling between FE and octahedral tilt modes, indicating that the coupling is competitive and prevents FE ordering. The onset of the orthorhombic phase is accompanied by sharp stiffening, analogous to the drop of permittivity, due to the hindered molecular dynamics. On further cooling, an intense anelastic relaxation process without a dielectric counterpart suggests the reorientation of clusters of molecules with strong antiferroelectric correlations.

Competition between polar and antiferrodistortive modes and correlated dynamics of the methylammonium molecules in MAPbI3 from anelastic and dielectric measurements / Cordero, Francesco; Craciun, Floriana; Trequattrini, Francesco; Imperatori, Patrizia; Paoletti, Anna Maria; Pennesi, Giovanna. - In: THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS. - ISSN 1948-7185. - STAMPA. - 9:15(2018), pp. 4401-4406. [10.1021/acs.jpclett.8b01761]

Competition between polar and antiferrodistortive modes and correlated dynamics of the methylammonium molecules in MAPbI3 from anelastic and dielectric measurements

Trequattrini, Francesco;
2018

Abstract

The mechanisms behind the exceptional photovoltaic properties of the metallorganic perovskites are still debated and include a ferroelectric (FE) state from the ordering of the electric dipoles of the organic molecules. We present the first anelastic (complex Young's modulus) and new dielectric measurements on CH3NH3PbI3, which provide new insight into the reorientation dynamics of the organic molecules and the reason why they do not form a FE state. The permittivity is fitted within the tetragonal phase with an expression that includes the coupling between FE and octahedral tilt modes, indicating that the coupling is competitive and prevents FE ordering. The onset of the orthorhombic phase is accompanied by sharp stiffening, analogous to the drop of permittivity, due to the hindered molecular dynamics. On further cooling, an intense anelastic relaxation process without a dielectric counterpart suggests the reorientation of clusters of molecules with strong antiferroelectric correlations.
2018
materials science (all)
01 Pubblicazione su rivista::01a Articolo in rivista
Competition between polar and antiferrodistortive modes and correlated dynamics of the methylammonium molecules in MAPbI3 from anelastic and dielectric measurements / Cordero, Francesco; Craciun, Floriana; Trequattrini, Francesco; Imperatori, Patrizia; Paoletti, Anna Maria; Pennesi, Giovanna. - In: THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS. - ISSN 1948-7185. - STAMPA. - 9:15(2018), pp. 4401-4406. [10.1021/acs.jpclett.8b01761]
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11573/1137544
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