Acoustic Phonon Lifetimes Limit Thermal Transport in Methylammonium Lead Iodide

Abstract

Hybrid organic-inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron-phonon coupling plays a critical role in all optoelectronic devices, and although the lattice dynamics and phonon frequencies of HOIPs have been well studied, little attention has been given to phonon lifetimes. We report the first high-precision measurements of acoustic phonon lifetimes in the hybrid perovskite methylammonium lead iodide (MAPI), using inelastic neutron spectroscopy to provide high energy resolution and fully deuterated single crystals to reduce incoherent scattering from hydrogen. Our measurements reveal extremely short lifetimes on the order of picoseconds, corresponding to nanometer mean free paths and demonstrating that acoustic phonons are unable to dissipate heat efficiently. Lattice-dynamics calculations using ab-initio third-order perturbation theory indicate that the short lifetimes stem from strong three-phonon interactions and a high density of low-energy optical phonon modes related to the degrees of freedom of the organic cation. Such short lifetimes have significant implications for electron-phonon coupling in MAPI and other HOIPs, with direct impacts on optoelectronic devices both in the cooling of hot carriers and in the transport and recombination of band edge carriers. These findings illustrate a fundamental difference between HOIPs and conventional photovoltaic semiconductors and demonstrate the importance of understanding lattice dynamics in the effort to develop metal halide perovskite optoelectronic devices.

arXiv comment31 pages, 14 figures

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• Direct evidence of weakly dispersed and strongly anharmonic optical phonons in hybrid perovskites
• Common acoustic phonon lifetimes in inorganic and hybrid lead halide perovskites
• The Disorder Origin of Raman Scattering In Perovskites Single Crystals
• Influence of Chloride Substitution on the Rotational Dynamics of Methylammonium in MAPbI${}_{3-x}$Cl${}_x$ Perovskites
• Decoupled molecular and inorganic framework dynamics in CH${}_3$NH${}_3$PbCl${}_3$
• On the question of dynamic domains and critical scattering in cubic methylammonium lead triiodide
• Time-resolved vibrational-pump visible-probe spectroscopy for thermal conductivity measurement of metal-halide perovskites
• Temporally-decoherent and spatially-coherent vibrations in metal halide perovskite
• Description of Excitonic Absorption Using the Sommerfeld Enhancement Factor and Band-Fluctuations
• Broadband critical dynamics in disordered lead-based perovskites
• Opto-thermal transport engineering in hybrid organic-inorganic lead halide perovskites metasurfaces
• Anharmonicity-driven Rashba co-helical excitons break quantum efficiency limitation
• Overscreening-free electron-phonon interaction in realistic materials
• Review: Solid-state physics of halide perovskites