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Cu Intercalation and Br Doping to Thermoelectric SnSe 2 Lead to Ultrahigh Electron Mobility and Temperature‐Independent Power Factor
Author(s) -
Zhou Chongjian,
Yu Yuan,
Zhang Xiangzhao,
Cheng Yudong,
Xu Jingtao,
Lee Yong Kyu,
Yoo Byeongjun,
CojocaruMirédin Oana,
Liu Guiwu,
Cho SungPyo,
Wuttig Matthias,
Hyeon Taeghwan,
Chung In
Publication year - 2020
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.201908405
Subject(s) - materials science , seebeck coefficient , thermoelectric effect , doping , electron mobility , condensed matter physics , thermoelectric materials , dopant , crystallite , effective mass (spring–mass system) , band gap , intercalation (chemistry) , electrical resistivity and conductivity , analytical chemistry (journal) , thermal conductivity , optoelectronics , inorganic chemistry , thermodynamics , chemistry , composite material , physics , quantum mechanics , electrical engineering , metallurgy , engineering , chromatography
Due to its single conduction band nature, it is highly challenging to enhance the power factor of SnSe 2 by band convergence. Here, it is reported that simultaneous Cu intercalation and Br doping induce strong Cu–Br interaction to connect SnSe 2 layers, otherwise isolated, via “electrical bridges.” Atom probe tomography analysis confirms a strong attraction between Cu intercalants and Br dopants in the SnSe 2 lattice. Density functional theory calculations reveal that this interaction delocalizes electrons confined around SnSe covalent bonds and enhances charge transfer across the SnSe 2 slabs. These effects dramatically increase electron mobility and concentration. Polycrystalline SnCu 0.005 Se 1.98 Br 0.02 shows even higher electron mobility than pristine SnSe 2 single crystal and the theoretical expectation. This results in significantly improved electrical conductivity without reducing effective mass and Seebeck coefficient, thereby leading to the highest power factor of ≈12 µW cm −1 K −2 to date for polycrystalline SnSe 2 and SnSe. It even surpasses the value for the state‐of‐the‐art n‐type SnSe 0.985 Br 0.015 single crystal at elevated temperatures. Surprisingly, the achieved power factor is nearly independent of temperature ranging from 300 to 773 K. The engineering thermoelectric figure of merit ZT eng for SnCu 0.005 Se 1.98 Br 0.02 is ≈0.25 between 773 and 300 K, the highest ZT eng ever reported for any form of SnSe 2 ‐based thermoelectric materials.