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

Cheng Chang; Minghui Wu; Dongsheng He; Yanling Pei; Chao-Feng Wu; Xuefeng Wu; Hulei Yu; Fangyuan Zhu; Kedong Wang; Yue Chen; Li Huang; Jing-Feng Li; Jiaqing He; Li-Dong Zhao

doi:10.1126/science.aaq1479

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

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

Authors

Cheng Chang¹, Minghui Wu², Dongsheng He², Yanling Pei¹, Chao-Feng Wu³, Xuefeng Wu², Hulei Yu⁴, Fangyuan Zhu⁵, Kedong Wang², Yue Chen⁴, Li Huang², Jing-Feng Li³, Jiaqing He⁶, Li-Dong Zhao⁷

Affiliations

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.

PMID: 29773748
DOI: 10.1126/science.aaq1479

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.

Publication types

Research Support, Non-U.S. Gov't