Abstract
Much recent attention has been devoted towards unraveling the microscopic optoelectronic properties of hybrid organic-inorganic perovskites. Here we investigate by coherent inelastic neutron scattering spectroscopy and Brillouin light scattering, low frequency acoustic phonons in four different hybrid perovskite single crystals: MAPbBr3, FAPbBr3, MAPbI3, and α-FAPbI3 (MA: methylammonium, FA: formamidinium). We report a complete set of elastic constants characterized by a very soft shear modulus C44. Further, a tendency towards an incipient ferroelastic transition is observed in FAPbBr3. We observe a systematic lower sound group velocity in the technologically important iodide-based compounds compared to the bromide-based ones. The findings suggest that low thermal conductivity and hot phonon bottleneck phenomena are expected to be enhanced by low elastic stiffness, particularly in the case of the ultrasoft α-FAPbI3.
Original language | English (US) |
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Article number | 085502 |
Journal | Physical Review Letters |
Volume | 121 |
Issue number | 8 |
DOIs | |
State | Published - Aug 22 2018 |
Bibliographical note
Publisher Copyright:© 2018 American Physical Society.
ASJC Scopus subject areas
- General Physics and Astronomy