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Science. 2018 May 18;360(6390):778-783. doi: 10.1126/science.aaq1479.

3D charge and 2D phonon transports leading to high out-of-plane ZT in n-type SnSe crystals.

Author information

1
School of Materials Science and Engineering, Beihang University, Beijing 100191, China.
2
Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China.
3
Key Laboratory of New Ceramics and Fine Processing, School of Materials Science and Engineering, Tsinghua University, Beijing 100084, China.
4
Department of Mechanical Engineering, The University of Hong Kong, Hong Kong SAR, China.
5
Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201204, China.
6
Department of Physics, Southern University of Science and Technology, Shenzhen 518055, China. he.jq@sustc.edu.cn zhaolidong@buaa.edu.cn.
7
School of Materials Science and Engineering, Beihang University, Beijing 100191, China. he.jq@sustc.edu.cn zhaolidong@buaa.edu.cn.

Abstract

Thermoelectric technology enables the harvest of waste heat and its direct conversion into electricity. The conversion efficiency is determined by the materials figure of merit ZT Here we show a maximum ZT of ~2.8 ± 0.5 at 773 kelvin in n-type tin selenide (SnSe) crystals out of plane. The thermal conductivity in layered SnSe crystals is the lowest in the out-of-plane direction [two-dimensional (2D) phonon transport]. We doped SnSe with bromine to make n-type SnSe crystals with the overlapping interlayer charge density (3D charge transport). A continuous phase transition increases the symmetry and diverges two converged conduction bands. These two factors improve carrier mobility, while preserving a large Seebeck coefficient. Our findings can be applied in 2D layered materials and provide a new strategy to enhance out-of-plane electrical transport properties without degrading thermal properties.

PMID:
29773748
DOI:
10.1126/science.aaq1479

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