A first-principles study of the effects of electron–phonon coupling on the thermoelectric properties: a case study of the SiGe compound

It is generally assumed in the thermoelectric community that the lattice thermal conductivity of a given material is independent of its electronic properties. This perspective is however questionable since the electron–phonon coupling could have certain effects on both the carrier and phonon transpo...

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Bibliographic Details
Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2018, Vol.6 (25), p.12125-12131
Main Authors: Fan, D. D., Liu, H. J., Cheng, L., Liang, J. H., Jiang, P. H.
Format: Article
Language:English
Subjects:
Carrier density
Case studies
Coupling (molecular)
Deformation
Electronic properties
Electrons
First principles
Heat conductivity
Heat transfer
High temperature
Lattice vibration
Potential theory
Relaxation time
Silicon germanides
Thermal conductivity
Thermoelectricity
Transport
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Summary:It is generally assumed in the thermoelectric community that the lattice thermal conductivity of a given material is independent of its electronic properties. This perspective is however questionable since the electron–phonon coupling could have certain effects on both the carrier and phonon transport, which in turn will affect the thermoelectric properties. Using the SiGe compound as a prototypical example, we give an accurate prediction of the carrier relaxation time by considering scattering from all the phonon modes, as opposed to the simple deformation potential theory. It is found that the carrier relaxation time does not change much with the concentration, which is however not the case for the phonon transport where the lattice thermal conductivity can be significantly reduced by electron–phonon coupling at higher carrier concentration. As a consequence, the figure-of-merit of the SiGe compound is obviously enhanced at optimized carrier concentration and becomes more pronounced at elevated temperature.
ISSN:2050-7488
2050-7496
DOI:10.1039/C8TA01806E