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Title: The effect of shallow vs. deep level doping on the performance of thermoelectric materials

It is well known that the efficiency of a good thermoelectric material should be optimized with respect to doping concentration. However, much less attention has been paid to the optimization of the dopant’s energy level. Thermoelectric materials doped with shallow levels may experience a dramatic reduction in their figures of merit at high temperatures due to the excitation of minority carriers that reduces the Seebeck coefficient and increases bipolar heat conduction. Doping with deep level impurities can delay the excitation of minority carriers as it requires a higher temperature to ionize all dopants. We find through modeling that, depending on the material type and temperature range of operation, different impurity levels (shallow or deep) will be desired to optimize the efficiency of a thermoelectric material. For different materials, we further clarify where the most preferable position of the impurity level within the bandgap falls. In this work, our research provides insight on why different dopants often affect thermoelectric transport properties differently and directions in searching for the most appropriate dopants for a thermoelectric material in order to maximize the device efficiency.
Authors:
ORCiD logo [1] ;  [1] ;  [1] ;  [2] ;  [3] ;  [1]
  1. Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States). Department of Mechanical Engineering
  2. Boston College, Chestnut Hill, MA (United States). Department of Physics
  3. University of Houston, TX (United States). Department of Physics and TcSUH
Publication Date:
Grant/Contract Number:
SC0001299; FG02-09ER46577
Type:
Accepted Manuscript
Journal Name:
Applied Physics Letters
Additional Journal Information:
Journal Volume: 109; Journal Issue: 26; Journal ID: ISSN 0003-6951
Publisher:
American Institute of Physics (AIP)
Research Org:
Massachusetts Inst. of Technology (MIT), Cambridge, MA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS
OSTI Identifier:
1465955
Alternate Identifier(s):
OSTI ID: 1337590