Direct evidence of weakly dispersed and strongly anharmonic optical phonons in hybrid perovskites

Abstract

Hybrid organolead perovskites (HOP) have started to establish themselves in the field of photovoltaics, mainly due to their great optoelectronic properties and steadily improving solar cell efficiency. Study of the lattice dynamics is key in understanding the electron-phonon interactions at play, responsible for such properties. Here, we investigate, via neutron and Raman spectroscopies, the optical phonon spectrum of four different HOP single crystals: MAPbBr${}_3$, FAPbBr${}_3$, MAPbI${}_3$, and $\alpha$-FAPbI${}_3$. Low temperature spectra reveal weakly dispersive optical phonons, at energies as low as 2-5~meV, which seem to be the origin of the limit of the charge carriers mobilities in these materials. The temperature dependence of our neutron spectra shows as well a significant anharmonic behaviour, resulting in optical phonon overdamping at temperatures as low as 80~K, questionning the validity of the quasi-particle picture for the low energy optical modes at room temperature where the solar cells operate.

6 figures, supplementary file (3 figures) included

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Cited by in corpus (18)

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• Vibrational relaxation dynamics in layered perovskite quantum wells
• Anharmonic lattice dynamics via the special displacement method
• Static and Dynamic Disorder in Formamidinium Lead Bromide Single Crystals
• Pseudospin-phonon pretransitional dynamics in lead halide hybrid perovskites
• Multiple lattice instabilities and complex ground state in Cs${}_2$AgBiBr${}_6$
• Controlling the electro-optic response of a semiconducting perovskite coupled to a phonon-resonant cavity
• Temperature-dependent EXAFS measurements of the Pb L3-edge allow quantification of the anharmonicity of the lead-halide bond of chlorine-substituted methylammonium (MA) lead triiodide
• Temporally-decoherent and spatially-coherent vibrations in metal halide perovskite
• Conductivity of an electron coupled to anharmonic phonons
• Terahertz Kerr effect in a methylammonium lead bromide perovskite crystal
• Efficient First-Principles Framework for Overdamped Phonon Dynamics and Anharmonic Electron-Phonon Coupling in Superionic Materials
• The fate of optical excitons in FAPbI3 nanocube superlattices
• Bond polarizability as a probe of local crystal fields in hybrid lead-halide perovskites
• Strongly Anharmonic Organic Cation Vibrations in Hybrid Lead Halide Perovskite CH3NH3PbI3 on Electronic Ground State
• Local structural disorder in crystalline materials
• Coherent Transfer of Lattice Entropy via Extreme Nonlinear Phononics in Metal Halide Perovskites
• Quantum beats of exciton-polarons in CsPbI3 perovskite nanocrystals