Weak Electron Phonon Coupling and Deep Level Impurity for High Thermoelectric Performance Pb1− xGaxTe

Xianli Su, Shiqiang Hao, Trevor P. Bailey, Si Wang, Ido Hadar, Gangjian Tan, Tze Bin Song, Qingjie Zhang, Ctirad Uher, Chris Wolverton, Xinfeng Tang, Mercouri G. Kanatzidis

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Abstract

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 Pb0.98Ga0.02Te 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 cm2 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.

Original languageEnglish
Article number1800659
JournalAdvanced Energy Materials
Volume8
Issue number21
DOIs
Publication statusPublished - Jul 25 2018

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Keywords

  • Ga doping
  • PbTe
  • deep level impurities
  • thermoelectric properties

ASJC Scopus subject areas

  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

Cite this

Su, X., Hao, S., Bailey, T. P., Wang, S., Hadar, I., Tan, G., Song, T. B., Zhang, Q., Uher, C., Wolverton, C., Tang, X., & Kanatzidis, M. G. (2018). Weak Electron Phonon Coupling and Deep Level Impurity for High Thermoelectric Performance Pb1− xGaxTe. Advanced Energy Materials, 8(21), [1800659]. https://doi.org/10.1002/aenm.201800659