Thesberg, Mischa, Kosina, Hans and Neophytou, Neophytos (2016) On the effectiveness of the thermoelectric energy filtering mechanism in low-dimensional superlattices and nano-composites. Journal of Applied Physics, 120 (23). 234302. doi:10.1063/1.4972192 ISSN 0021-8979.

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Abstract

Electron energy filtering has been suggested as a promising way to improve the power factor and enhance the ZT figure of merit of thermoelectric materials. In this work, we explore the effect that reduced dimensionality has on the success of the energy-filtering mechanism for power factor enhancement. We use the quantum mechanical non-equilibrium Green's function method for electron transport including electron-phonon scattering to explore 1D and 2D superlattice/nanocomposite systems. We find that, given identical material parameters, 1D channels utilize energy filtering more effectively than 2D as they: (i) allow one to achieve the maximal power factor for smaller well sizes/smaller grains which are needed to maximize the phonon scattering, (ii) take better advantage of a lower thermal conductivity in the barrier/boundary materials compared to the well/grain materials in both: enhancing the Seebeck coefficient; and in producing a system which is robust against detrimental random deviations from the optimal barrier design. In certain cases, we find that the relative advantage can be as high as a factor of 3. We determine that energy-filtering is most effective when the average energy of carrier flow varies the most between the wells and the barriers along the channel, an event which occurs when the energy of the carrier flow in the host material is low, and when the energy relaxation mean-free-path of carriers is short. Although the ultimate reason for these aspects, which cause a 1D system to see greater relative improvement than a 2D, is the 1D system's van Hove singularity in the density-of-states, the insights obtained are general and inform energy-filtering design beyond dimensional considerations.

Item Type:	Journal Article
Subjects:	Q Science > QC Physics T Technology > TA Engineering (General). Civil engineering (General)
Divisions:	Faculty of Science, Engineering and Medicine > Engineering > Engineering
Library of Congress Subject Headings (LCSH):	Nanocomposites (Materials) -- Thermomechanical properties , Electrical engineering, Superlattices as materials
Journal or Publication Title:	Journal of Applied Physics
Publisher:	American Institute of Physics
ISSN:	0021-8979
Official Date:	December 2016
Dates:	Date Event December 2016 Available 1 December 2016 Accepted
Volume:	120
Number:	23
Article Number:	234302
DOI:	10.1063/1.4972192
Status:	Peer Reviewed
Publication Status:	Published
Access rights to Published version:	Restricted or Subscription Access
Date of first compliant deposit:	22 December 2016
Date of first compliant Open Access:	22 December 2016
Funder:	Österreichische Forschungsförderungsgesellschaft (FFG), Fonds zur Förderung der Wissenschaftlichen Forschung (Austria) (FWF), Horizon 2020 (European Commission) (H2020)
Grant number:	project 850743 QTSMoS (FFG), contract P25368-N30 (FWF), Grant agreement No 678763 (H2020)

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