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

Jianfeng Yang, Xiaoming Wen*, Hongze Xia, Rui Sheng, Qingshan Ma, Jincheol Kim, Patrick Tapping, Takaaki Harada, Tak W. Kee, Fuzhi Huang, Yi-Bing Cheng, Martin Green, Anita Ho-Baillie, Shujuan Huang, Santosh Shrestha, Robert Patterson, Gavin Conibeer

*Corresponding author for this work

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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.

Original languageEnglish
Article number14120
Number of pages9
JournalNature Communications
Publication statusPublished - 20 Jan 2017
Externally publishedYes

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