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Journal ArticleDOI: 10.1039/D0TA08683E

Anomalous enhancement of thermoelectric power factor by thermal management with resonant level effect

02 Mar 2021-Journal of Materials Chemistry (Royal Society of Chemistry (RSC))-Vol. 9, Iss: 8, pp 4851-4857
Abstract: Obtaining high thermoelectric performance has been the biggest historical challenge for thermoelectric power generation Here, we propose a methodology for thermoelectric power factor enhancement: thermal management with resonant level effect for simultaneous increase of electrical conductivity σ and Seebeck coefficient S Au crystals and Au impurities are introduced into SiGe Therein, (1) highly-conductive Au crystals increased σ (2) Au impurities brought about resonant level effect and phonon scattering, resulting in enhanced S and lowered thermal conductivity κ of SiGe (3) This κ distribution control brings the focus of temperature difference on SiGe parts with lowered κ, resulting in the availability of the enhanced S of SiGe parts as effective S of the entire nanocomposite Consequently, we achieved the highest S2σ at room temperature among SiGe-related materials ever reported Electronic structure calculation and measurement support the existence of resonant levels, which enhances S and lowers κ These results provide a new route to thermoelectric performance enhancement

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Topics: Thermoelectric effect (62%), Seebeck coefficient (60%), Thermoelectric generator (57%) ... show more
Citations
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6 results found


Open accessJournal Article
Abstract: The simultaneous realization of low thermal conductivity and high thermoelectric power factor in materials has long been the goal for the social use of high-performance thermoelectric modules. Nanostructuring approaches have drawn considerable attention because of the success in reducing thermal conductivity. On the contrary, enhancement of the thermoelectric power factor, namely, the simultaneous increase of the Seebeck coefficient and electrical conductivity, has been difficult. We propose a method for the power factor enhancement by introducing coherent homoepitaxial interfaces with controlled dopant concentration, which enables the quasiballistic transmission of high-energy carriers. The wavenumber of the high-energy carriers is nearly conserved through the interfaces, resulting in simultaneous realization of a high Seebeck coefficient and relatively high electrical mobility. Here, we experimentally demonstrate the dopant-controlled epitaxial interface effect for the thermoelectric power factor enhancement using our \"embedded-ZnO nanowire structure\" having high-quality nanowire interfaces. This presents the methodology for substantial power factor enhancement by interface carrier scattering.

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Topics: Thermoelectric materials (59%), Surface science (51%), Nanowire (50%)

33 Citations



Journal ArticleDOI: 10.1016/J.JALLCOM.2021.161306
Takuto Mizoguchi1, Toshifumi Imajo1, Jun Chen2, Takashi Sekiguchi1  +2 moreInstitutions (2)
Abstract: Group-IV alloy semiconductors have garnered increasing attention as advanced thin-film materials for next-generation electronics. We have demonstrated polycrystalline Ge thin films with the highest recorded crystallinity and carrier mobility using a multistep heating process in solid-phase crystallization. In this study, we apply these recent findings in Ge to Si1-xGex (x: 0–1) and Ge1-ySny (y: 0–0.04) alloys and investigate their crystal and electrical properties. For all compositions, controlling the temperature in each stage increases the grain size to the micrometer order, improving the carrier mobility and reducing the number of defect-induced acceptors. Sb doping further enlarges the grain size (up to 10 µm) in addition to n-type conduction control, whereas the electron concentration varies with the composition. Both hole and electron mobilities significantly depend on the composition owing to the effects of carrier effective mass, grain size, and carrier concentration: the hole and electron mobilities peak at 350 and 150 cm2 V−1s−1, respectively. The relationship between the composition and various physical properties revealed in this study will contribute to the better understanding, control, and device application of polycrystalline thin films based on group-IV alloy semiconductors.

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Topics: Electron mobility (58%), Crystallite (53%), Doping (53%) ... show more

Journal ArticleDOI: 10.1016/J.CEJ.2021.132738
Deyu Bao1, Qiang Sun2, Linsen Huang1, Jie Chen1  +6 moreInstitutions (3)
Abstract: Tremendous efforts have been focusing on the improvement of p-type (Bi, Sb)2Te3-based thermoelectric materials for commercial applications. In this study, we achieve versatile interface engineering through a surface decoration of Bi0.5Sb1.5Te3 by amorphous Sb2S3 combining with spark plasma sintering, which introduces semi-coherent Sb/Bi0.5Sb1.5Te3 interfaces and dopes S into Bi0.5Sb1.5Te3. Semi-coherent Sb/Bi0.5Sb1.5Te3 interfaces strongly scatter phonons and lower energy carriers, leading to decreased thermal conductivity and increased Seebeck coefficient, while the electrical conductivity is not sacrificed due to the compromise of the slightly reduced carrier mobility by interfacial scattering and the increased carrier concentration by S doping. Benefited from the decoupled thermoelectric properties, a significantly enhanced power factor of 3345.40 μW m−1 K−2 and a low thermal conductivity of 0.78 W m−1 K−1 is obtained in Bi0.5Sb1.5Te3-0.4%Sb2S3, leading to a high peak zT of ∼ 1.31 at 330 K, which shows a 54% enhancement compared with pristine Bi0.5Sb1.5Te3. Moreover, a conversion efficiency of ∼ 7.6% can be predicted in a single leg Bi0.5Sb1.5Te3-0.4%Sb2S3-based module under a cold side temperature of 300 K and hot side temperature of 480 K. This study paves a facile amorphous Sb2S3 induced interface engineering strategy for the development of high performance (Bi,Sb)2Te3-based thermoelectric materials.

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Topics: Thermoelectric materials (66%), Thermoelectric effect (62%), Seebeck coefficient (59%) ... show more


References
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54 results found


Journal ArticleDOI: 10.1038/NATURE06381
10 Jan 2008-Nature
Abstract: Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

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Topics: Thermoelectric materials (70%), Thermoelectric effect (66%), Seebeck coefficient (65%) ... show more

3,446 Citations


Journal ArticleDOI: 10.1038/NATURE11439
Kanishka Biswas1, Jiaqing He1, Ivan Blum2, Ivan Blum1  +7 moreInstitutions (5)
20 Sep 2012-Nature
Abstract: Controlling the structure of thermoelectric materials on all length scales (atomic, nanoscale and mesoscale) relevant for phonon scattering makes it possible to increase the dimensionless figure of merit to more than two, which could allow for the recovery of a significant fraction of waste heat with which to produce electricity.

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3,075 Citations


Journal ArticleDOI: 10.1126/SCIENCE.1159725
25 Jul 2008-Science
Abstract: The efficiency of thermoelectric energy converters is limited by the material thermoelectric figure of merit (zT). The recent advances in zT based on nanostructures limiting the phonon heat conduction is nearing a fundamental limit: The thermal conductivity cannot be reduced below the amorphous limit. We explored enhancing the Seebeck coefficient through a distortion of the electronic density of states and report a successful implementation through the use of the thallium impurity levels in lead telluride (PbTe). Such band structure engineering results in a doubling of zT in p-type PbTe to above 1.5 at 773 kelvin. Use of this new physical principle in conjunction with nanostructuring to lower the thermal conductivity could further enhance zT and enable more widespread use of thermoelectric systems.

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Topics: Thermoelectric materials (66%), Thermoelectric effect (61%), Seebeck coefficient (61%) ... show more

2,937 Citations


Open accessJournal Article
Abstract: Approximately 90 per cent of the world’s power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30–40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2–4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20–300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

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Topics: Thermoelectric effect (62%)

2,814 Citations


Journal ArticleDOI: 10.1038/NATURE09996
Yanzhong Pei1, Xiaoya Shi2, Aaron D. LaLonde1, Heng Wang1  +2 moreInstitutions (2)
05 May 2011-Nature
Abstract: Thermoelectric generators, which directly convert heat into electricity, have long been relegated to use in space-based or other niche applications, but are now being actively considered for a variety of practical waste heat recovery systems—such as the conversion of car exhaust heat into electricity. Although these devices can be very reliable and compact, the thermoelectric materials themselves are relatively inefficient: to facilitate widespread application, it will be desirable to identify or develop materials that have an intensive thermoelectric materials figure of merit, zT, above 1.5 (ref. 1). Many different concepts have been used in the search for new materials with high thermoelectric efficiency, such as the use of nanostructuring to reduce phonon thermal conductivity, which has led to the investigation of a variety of complex material systems. In this vein, it is well known, that a high valley degeneracy (typically ≤6 for known thermoelectrics) in the electronic bands is conducive to high zT, and this in turn has stimulated attempts to engineer such degeneracy by adopting low-dimensional nanostructures. Here we demonstrate that it is possible to direct the convergence of many valleys in a bulk material by tuning the doping and composition. By this route, we achieve a convergence of at least 12 valleys in doped PbTe_(1) − _(x)Se_(x) alloys, leading to an extraordinary zT value of 1.8 at about 850 kelvin. Band engineering to converge the valence (or conduction) bands to achieve high valley degeneracy should be a general strategy in the search for and improvement of bulk thermoelectric materials, because it simultaneously leads to a high Seebeck coefficient and high electrical conductivity.

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Topics: Thermoelectric materials (62%), Thermoelectric effect (60%), Thermoelectric generator (58%) ... show more

2,553 Citations


Performance
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No. of citations received by the Paper in previous years
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