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Title: Divalent doping-induced thermoelectric power factor increase in p-type Bi 2Te 3 via electronic structure tuning

Abstract

We use first-principles calculations to reveal the effects of divalent Pb, Ca, and Sn doping of Bi 2Te 3 on the band structure and transport properties, including the Seebeck coefficient, α, and the reduced power factor, α 2σ/τ, where σ is the electrical conductivity and τ is the effective relaxation time. Pb and Ca additions exhibit up to 60%–75% higher peak α 2σ/τ than that of intrinsic Bi 2Te 3 with Bi antisite defects. Pb occupancy and Ca occupancy of Bi sites increase σ/τ by activating high-degeneracy low-effective-mass bands near the valence band edge, unlike Bi antisite occupancy of Te sites that eliminates near-edge valence states in intrinsic Bi 2Te 3. Neither Pb doping nor subatomic-percent Ca doping increases α significantly, due to band averaging. Higher Ca levels increase α and diminish σ, due to the emergence of a corrugated band structure underpinned by high-effective-mass bands, attributable to Ca–Te bond ionicity. Sn doping results in a distortion of the bands with a higher density of states that may be characterized as a resonant state but decreases α 2σ by up to 30% due to increases in the charge carrier effective mass and decreases in both spin–orbit coupling and valence bandmore » quasidegeneracy. These results, and thermal conductivity calculations for nanostructured Bi 2Te 3, suggest that Pb or Ca doping can enhance the thermoelectric figure of merit ZT to values up to ZT ~ 1.7, based on an experimentally determined τ. Our findings suggest that divalent doping can be attractive for realizing large ZT enhancements in pnictogen chalcogenides.« less

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [3]; ORCiD logo [1];  [1]
  1. Rensselaer Polytechnic Inst., Troy, NY (United States)
  2. Univ. of Michigan, Ann Arbor, MI (United States)
  3. Univ. of Missouri, Columbia, MO (United States)
Publication Date:
Research Org.:
Energy Frontier Research Centers (EFRC) (United States). Solid-State Solar-Thermal Energy Conversion Center (S3TEC); Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1566659
Alternate Identifier(s):
OSTI ID: 1508203
Grant/Contract Number:  
SC0001299; SC0001299/DE-FG02-09ER4657
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Applied Physics
Additional Journal Information:
Journal Volume: 125; Journal Issue: 16; Journal ID: ISSN 0021-8979
Publisher:
American Institute of Physics (AIP)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; solar (photovoltaic), solar (thermal), solid state lighting, phonons, thermal conductivity, thermoelectric, defects, mechanical behavior, charge transport, spin dynamics, materials and chemistry by design, optics, synthesis (novel materials), synthesis (self-assembly), synthesis (scalable processing)

Citation Formats

Gaul, Andrew, Peng, Qing, Singh, David J., Borca-Tasciuc, Theodorian, and Ramanath, Ganpati. Divalent doping-induced thermoelectric power factor increase in p-type Bi2Te3 via electronic structure tuning. United States: N. p., 2019. Web. doi:10.1063/1.5081438.
Gaul, Andrew, Peng, Qing, Singh, David J., Borca-Tasciuc, Theodorian, & Ramanath, Ganpati. Divalent doping-induced thermoelectric power factor increase in p-type Bi2Te3 via electronic structure tuning. United States. doi:10.1063/1.5081438.
Gaul, Andrew, Peng, Qing, Singh, David J., Borca-Tasciuc, Theodorian, and Ramanath, Ganpati. Mon . "Divalent doping-induced thermoelectric power factor increase in p-type Bi2Te3 via electronic structure tuning". United States. doi:10.1063/1.5081438.
@article{osti_1566659,
title = {Divalent doping-induced thermoelectric power factor increase in p-type Bi2Te3 via electronic structure tuning},
author = {Gaul, Andrew and Peng, Qing and Singh, David J. and Borca-Tasciuc, Theodorian and Ramanath, Ganpati},
abstractNote = {We use first-principles calculations to reveal the effects of divalent Pb, Ca, and Sn doping of Bi2Te3 on the band structure and transport properties, including the Seebeck coefficient, α, and the reduced power factor, α2σ/τ, where σ is the electrical conductivity and τ is the effective relaxation time. Pb and Ca additions exhibit up to 60%–75% higher peak α2σ/τ than that of intrinsic Bi2Te3 with Bi antisite defects. Pb occupancy and Ca occupancy of Bi sites increase σ/τ by activating high-degeneracy low-effective-mass bands near the valence band edge, unlike Bi antisite occupancy of Te sites that eliminates near-edge valence states in intrinsic Bi2Te3. Neither Pb doping nor subatomic-percent Ca doping increases α significantly, due to band averaging. Higher Ca levels increase α and diminish σ, due to the emergence of a corrugated band structure underpinned by high-effective-mass bands, attributable to Ca–Te bond ionicity. Sn doping results in a distortion of the bands with a higher density of states that may be characterized as a resonant state but decreases α2σ by up to 30% due to increases in the charge carrier effective mass and decreases in both spin–orbit coupling and valence band quasidegeneracy. These results, and thermal conductivity calculations for nanostructured Bi2Te3, suggest that Pb or Ca doping can enhance the thermoelectric figure of merit ZT to values up to ZT ~ 1.7, based on an experimentally determined τ. Our findings suggest that divalent doping can be attractive for realizing large ZT enhancements in pnictogen chalcogenides.},
doi = {10.1063/1.5081438},
journal = {Journal of Applied Physics},
number = 16,
volume = 125,
place = {United States},
year = {2019},
month = {4}
}

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Efficiency of ab-initio total energy calculations for metals and semiconductors using a plane-wave basis set
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Efficient iterative schemes for ab initio total-energy calculations using a plane-wave basis set
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Complex thermoelectric materials
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