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Weak Electron Phonon Coupling and Deep Level Impurity for High Thermoelectric Performance Pb 1− x Ga x Te
Author(s) -
Su Xianli,
Hao Shiqiang,
Bailey Trevor P.,
Wang Si,
Hadar Ido,
Tan Gangjian,
Song TzeBin,
Zhang Qingjie,
Uher Ctirad,
Wolverton Chris,
Tang Xinfeng,
Kanatzidis Mercouri G.
Publication year - 2018
Publication title -
advanced energy materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 10.08
H-Index - 220
eISSN - 1614-6840
pISSN - 1614-6832
DOI - 10.1002/aenm.201800659
Subject(s) - materials science , impurity , doping , condensed matter physics , thermoelectric effect , phonon , seebeck coefficient , atmospheric temperature range , electron mobility , ionized impurity scattering , coupling (piping) , phonon scattering , scattering , thermal conductivity , optoelectronics , physics , optics , thermodynamics , quantum mechanics , metallurgy , composite material
High ZT of 1.34 at 766 K and a record high average ZT above 1 in the temperature range of 300‐864 K are attained in n‐type PbTe by engineering the temperature‐dependent carrier concentration and weakening electron–phonon coupling upon Ga doping. The experimental studies and first principles band structure calculations show that doping with Ga introduces a shallow level impurity contributing extrinsic carriers and imparts a deeper impurity level that ionizes at higher temperatures. This adjusts the carrier concentration closer to the temperature‐dependent optimum and thus maximizes the power factor in a wide temperature range. The maximum power factor of 35 µW cm −1 K −2 is achieved for the Pb 0.98 Ga 0.02 Te compound, and is maintained over 20 µWcm −1 K −2 from 300 to 767 K. Band structure calculations and X‐ray photoelectron spectroscopy corroborate the amphoteric role of Ga in PbTe as the origin of shallow and deep levels. Additionally, Ga doping weakens the electron–phonon coupling, leading to high carrier mobilities in excess of 1200 cm 2 V −1 s −1 . Enhanced point defect phonon scattering yields a reduced lattice thermal conductivity. This work provides a new avenue, beyond the conventional shallow level doping, for further improving the average ZT in thermoelectric materials.