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)|
|Journal||Physical Review Letters|
|State||Published - Aug 22 2018|
Bibliographical noteFunding Information:
This project has received funding from the European Union’s Horizon 2020 programme, through a FET Open research and innovation action under the Grant agreement No. 687008. M. I. S. acknowledges the support of Banting Postdoctoral Fellowship Program, administered by the Government of Canada.
© 2018 American Physical Society.
ASJC Scopus subject areas
- Physics and Astronomy(all)