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Nat Commun. 2017 Jan 20;8:14120. doi: 10.1038/ncomms14120.

Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.

Author information

1
Australian Centre for Advanced Photovoltaics, School of Photovoltaics and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia.
2
Centre for Micro-Photonics, Swinburne University of Technology, Melbourne, Victoria 3122, Australia.
3
Department of Chemistry, The University of Adelaide, Adelaide, South Australia 5005, Australia.
4
State Key Lab of Advanced Technologies for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070, China.
5
Department of Materials Science and Engineering, Monash University, Melbourne, Victoria 3800, Australia.

Abstract

The hot-phonon bottleneck effect in lead-halide perovskites (APbX3) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA+/MA+/Cs+, X=I-/Br-) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI3. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.

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