Giant isotope effect on phonon dispersion and thermal conductivity in methylammonium lead iodide
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
- Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
- Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA.
- Department of Materials Science and Engineering, University of California, Berkeley, Berkeley, CA 94720, USA., Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
- Joint Institute for Advanced Materials, Department of Materials Science and Engineering, University of Tennessee, Knoxville, TN 37996, USA.
Lead halide perovskites are strong candidates for high-performance low-cost photovoltaics, light emission, and detection applications. A hot-phonon bottleneck effect significantly extends the cooling time of hot charge carriers, which thermalize through carrier-optic phonon scattering, followed by optic phonon decay to acoustic phonons and finally thermal conduction. To understand these processes, we adjust the lattice dynamics independently of electronics by changing isotopes. We show that doubling the mass of hydrogen in methylammonium lead iodide by replacing protons with deuterons causes a large 20 to 50% softening of the longitudinal acoustic phonons near zone boundaries, reduces thermal conductivity by ~50%, and slows carrier relaxation kinetics. Phonon softening is attributed to anticrossing with the slowed libration modes of the deuterated molecules and the reduced thermal conductivity to lowered phonon velocities. Our results reveal how tuning the organic molecule dynamics enables control of phonons important to thermal conductivity and the hot-phonon bottleneck.
- Research Organization:
- Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES); US Department of Homeland Security (DHS); USDOE Office of Energy Efficiency and Renewable Energy (EERE), Transportation Office. Vehicle Technologies Office
- Grant/Contract Number:
- AC02-05-CH11231; AC05-00OR22725; AC02-05CH11231; 16DNARI00018-04-0
- OSTI ID:
- 1644246
- Alternate ID(s):
- OSTI ID: 1649411; OSTI ID: 1695741
- Journal Information:
- Science Advances, Journal Name: Science Advances Vol. 6 Journal Issue: 31; ISSN 2375-2548
- Publisher:
- AAASCopyright Statement
- Country of Publication:
- United States
- Language:
- English
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