We present an analytical model for the Seebeck coefficient of superlattice materials that explicitly takes into account the energy relaxation due to electron-optical phonon (e-ph) scattering. In such materials, the Seebeck coefficient is not only determined by the bulk Seebeck values of the materials but, in addition, is dependent on the energy relaxation process of charge carriers as they propagate from the less-conductive barrier region into the more-conductive well region. We calculate as a function of the well size , where carrier energy becomes increasingly relaxed within the well for , where is the energy relaxation length. We validate the model against more advanced quantum transport simulations based on the nonequilibrium Green’s function (NEGF) method and also with an experiment, and we find very good agreement. In the case in which no energy relaxation is taken into account, the results deviate substantially from the NEGF results. The model also yields accurate results with only a small deviation (up to ) when varying the optical phonon energy or the e-ph coupling strength , physical parameters that would determine . As a first order approximation, the model is valid for nanocomposite materials, and it could prove useful in the identification of material combinations and in the estimation of ideal sizes in the design of nanoengineered thermoelectric materials with enhanced power factor performance.
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7 August 2019
Research Article|
August 01 2019
Theoretical model for the Seebeck coefficient in superlattice materials with energy relaxation
Special Collection:
Advanced Thermoelectrics
Vassilios Vargiamidis
;
Vassilios Vargiamidis
a)
1
School of Engineering, University of Warwick
, Coventry CV4 7AL, United Kingdom
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Mischa Thesberg
;
Mischa Thesberg
2
Institute for Microelectronics, Technical University of Vienna
, Vienna A-1040, Austria
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Neophytos Neophytou
Neophytos Neophytou
1
School of Engineering, University of Warwick
, Coventry CV4 7AL, United Kingdom
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a)
Electronic mail: V.Vargiamidis@warwick.ac.uk
Note: This paper is part of the special topic on Advanced Thermoelectrics.
J. Appl. Phys. 126, 055105 (2019)
Article history
Received:
April 30 2019
Accepted:
July 13 2019
Citation
Vassilios Vargiamidis, Mischa Thesberg, Neophytos Neophytou; Theoretical model for the Seebeck coefficient in superlattice materials with energy relaxation. J. Appl. Phys. 7 August 2019; 126 (5): 055105. https://doi.org/10.1063/1.5108607
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