Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

Narducci, Dario; Selezneva, Ekaterina; Cerofolini, G. F.; Frabboni, Stefano; Ottaviani, G.

doi:10.1016/j.jssc.2012.03.032

Cited by 170 publications

(96 citation statements)

References 26 publications

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“…According to theoretical considerations, energy filtering can arise from extended barriers such as heterostructures, nanocomposites, nanoinclusions, or grain boundaries. [9][10][11][12][13][15][16][17] A. Electronic structure calculations…”

Section: Theorymentioning

confidence: 99%

“…By introducing potential barriers or strongly energy-dependent scattering mechanisms, low-energetic carriers can be blocked, greatly enhancing the Seebeck coefficient. 7,[9][10][11][12][13][14][15][16][17][18] ZnSb has been known as a thermoelectric material for a long time. 19 When Caillat reported a figure of merit of 1.4 for Zn 4 Sb 3 in 1997, that composition got the most attention due to the remarkably low thermal conductivity.…”

Section: Introductionmentioning

confidence: 99%

“…32 Our hypothesis was that such processing could introduce energy filtering from grain boundaries or nanoinclusions associated with grain boundaries. 13,15,17 The transport properties of these samples were then compared to the theoretical predictions with and without energy filtering. This paper is organized as follows: First, a brief description of the sample preparation and experimental methods are provided.…”

Section: Introductionmentioning

confidence: 99%

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Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Berland

Song

Carvalho

et al. 2016

Journal of Applied Physics

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Energy filtering has been suggested by many authors as a means to improve thermoelectric properties. The idea is to filter away low-energy charge carriers in order to increase Seebeck coefficient without compromising electronic conductivity. This concept was investigated in the present paper for a specific material (ZnSb) by a combination of first-principles atomic-scale calculations, Boltzmann transport theory, and experimental studies of the same system. The potential of filtering in this material was first quantified, and it was as an example found that the power factor could be enhanced by an order of magnitude when the filter barrier height was 0.5 eV. Measured values of the Hall carrier concentration in bulk ZnSb were then used to calibrate the transport calculations, and nanostructured ZnSb with average grain size around 70 nm was processed to achieve filtering as suggested previously in the literature. Various scattering mechanisms were employed in the transport calculations and compared with the measured transport properties in nanostructured ZnSb as a function of temperature. Reasonable correspondence between theory and experiment could be achieved when a combination of constant lifetime scattering and energy filtering with a 0.25 eV barrier was employed. However, the difference between bulk and nanostructured samples was not sufficient to justify the introduction of an energy filtering mechanism. The reasons for this and possibilities to achieve filtering were discussed in the paper.

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Section: Theorymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Berland

Song

Carvalho

et al. 2016

Journal of Applied Physics

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“…Thus, increasing such conversion efficiency requires both high ZT and a large temperature gradient across the materials. One effective way to achieve high ZT is to reduce lattice thermal conductivity through embedding micro/nanostructures, which provide multiple scattering mechanisms for phonons 1,2,[4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] . Other strategies address the challenge of maximizing a power factor from existing semiconducting materials by band alignment 5,6,19,20 , modifying their electronic structures close to the Fermi level 21,22 , and increasing band degeneracy by convergence of bands 23 .…”

mentioning

confidence: 99%

Contrasting role of antimony and bismuth dopants on the thermoelectric performance of lead selenide

et al. 2014

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Increasing the conversion efficiency of thermoelectric materials is a key scientific driver behind a worldwide effort to enable heat to electricity power generation at competitive cost. Here we report an increased performance for antimony-doped lead selenide with a thermoelectric figure of merit of B1.5 at 800 K. This is in sharp contrast to bismuth doped lead selenide, which reaches a figure of merit of o1. Substituting antimony or bismuth for lead achieves maximum power factors between B23-27 mWcm À 1 K À 2 at temperatures above 400 K. The addition of small amounts (B0.25 mol%) of antimony generates extensive nanoscale precipitates, whereas comparable amounts of bismuth results in very few or no precipitates. The antimony-rich precipitates are endotaxial in lead selenide, and appear remarkably effective in reducing the lattice thermal conductivity. The corresponding bismuth-containing samples exhibit smaller reduction in lattice thermal conductivity.

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“…The work of Ref. [12,16] has demonstrated very high power factors in Si-based nanocomposites, however energy filtering was only partially responsible for this. Surprisingly, despite the fact that the energy filtering idea was suggested in the 1998 [5], still there is no theoretical investigation as to why power factor benefits are hard to realize experimentally.…”

Section: Introductionmentioning

confidence: 99%

The Fragility of Thermoelectric Power Factor in Cross-Plane Superlattices in the Presence of Nonidealities: A Quantum Transport Simulation Approach

Thesberg

Pourfath

Neophytou

et al. 2015

Journal of Elec Materi

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Original citation: Thesberg, M., Pourfath, M., Neophytou, Neophytos and Kosina, H.. (2016) The fragility of thermoelectric power factor in cross-plane superlattices in the presence of nonidealities : a quantum transport simulation approach. Journal of Electronic Materials, 45 (3). pp. 1584-1588. Permanent WRAP url:http://wrap.warwick.ac.uk/77432 Copyright and reuse:The Warwick Research Archive Portal (WRAP) makes this work by researchers of the University of Warwick available open access under the following conditions. Copyright © and all moral rights to the version of the paper presented here belong to the individual author(s) and/or other copyright owners. To the extent reasonable and practicable the material made available in WRAP has been checked for eligibility before being made available.Copies of full items can be used for personal research or study, educational, or not-for profit purposes without prior permission or charge. Provided that the authors, title and full bibliographic details are credited, a hyperlink and/or URL is given for the original metadata page and the content is not changed in any way. Publisher's statement:"The final publication is available at Springer via http://dx.doi.org/10.1007/s11664-015-4124-7 ." A note on versions:The version presented here may differ from the published version or, version of record, if you wish to cite this item you are advised to consult the publisher's version. Please see the 'permanent WRAP url' above for details on accessing the published version and note that access may require a subscription. AbstractEnergy filtering has been put forth as a promising method for achieving large thermoelectric power factors in thermoelectric materials through Seebeck coefficient improvements. Materials with embedded potential barriers, such as cross-plane superlattices provide energy filtering, in addition to low thermal conductivities, and could potentially achieve high figures of merit. Although there exist many theoretical works demonstrating Seebeck coefficient and power factor gains in idealized structures, experimental support has been scant. In most cases the electrical conductivity is drastically reduced due to the presence of barriers. In this work, using quantum mechanical simulations based on the Non-Equilibrium Green's Function method, we show that although power factor improvements can theoretically be observed in 1 optimized superlattices (something pointed out in previous studies), different types of deviations from the ideal potential profiles of the barriers degrade the performance. Some non-idealities being so significant as to negate all power factor gains. Specifically, the effect of tunneling due to thin barriers could be especially detrimental to the Seebeck coefficient and the power factor. Our results could partially explain why significant power factor improvements in superlattices and other energy filtering nanostructures mainly fail to be realized, despite theoretical predictions.

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Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

Cited by 170 publications

References 26 publications

Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

Contrasting role of antimony and bismuth dopants on the thermoelectric performance of lead selenide

The Fragility of Thermoelectric Power Factor in Cross-Plane Superlattices in the Presence of Nonidealities: A Quantum Transport Simulation Approach

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