The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Jeffrey G Snyder - One of the best experts on this subject based on the ideXlab platform.
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low electron scattering Potentials in high performancemg_2si_ 0 45 sn_ 0 55 based thermoelectric solid solutions with band convergence
Advanced Energy Materials, 2013Co-Authors: Xiaohua Liu, Jeffrey G Snyder, Heng Wang, Tiejun Zhu, Hanhui Xie, Guangyu Jiang, Xinbing ZhaoAbstract:Understanding the electron and phonon transport characteristics is crucial for designing and developing high performance thermoelectric materials. Weak scattering effects on charge carriers, characterized by Deformation Potential and alloy scattering Potential, are favorable for thermoelectric solid solutions to enable high carrier mobility and thereby promising thermoelectric performance. Mg_2(Si,Sn) solid solutions have attracted much attention due to their low cost and environmental compatibility. Usually, their high thermoelectric performance with ZT ∼ 1 is ascribed to the band convergence and reduced lattice thermal conductivity caused by alloying. In this work, both a low Deformation Potential Ξ = 13 eV and a low alloy scattering Potential U = 0.7 eV are found for the thermoelectric alloys by characterizing and modeling of thermoelectric transport properties. The band convergence is also verified by the increased density-of-states effective mass. It is proposed that, in addition to band convergence and reduced lattice thermal conductivity, the low Deformation Potential and alloy scattering Potential are additional intrinsic features that contribute to the high thermoelectric performance of the solid solutions.
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low effective mass leading to high thermoelectric performance
Energy and Environmental Science, 2012Co-Authors: Aaron D. Lalonde, Heng Wang, Jeffrey G SnyderAbstract:High Seebeck coefficient by creating large density-of-states effective mass through either electronic structure modification or manipulating nanostructures is commonly considered as a route to advanced thermoelectrics. However, large density-of-state due to flat bands leads to large transport effective mass, which results in a simultaneous decrease of mobility. In fact, the net effect of such a high effective mass is a lower thermoelectric figure of merit, zT, when the carriers are predominantly scattered by phonons according to the Deformation Potential theory of Bardeen–Shockley. We demonstrate that the beneficial effect of light effective mass contributes to high zT in n-type thermoelectric PbTe, where doping and temperature can be used to tune the effective mass. This clear demonstration of the Deformation Potential theory to thermoelectrics shows that the guiding principle for band structure engineering should be low effective mass along the transport direction.
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weak electron phonon coupling contributing to high thermoelectric performance in n type pbse
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Heng Wang, Aaron D. Lalonde, Yanzhong Pei, Jeffrey G SnyderAbstract:PbSe is a surprisingly good thermoelectric material due, in part, to its low thermal conductivity that had been overestimated in earlier measurements. The thermoelectric figure of merit, zT, can exceed 1 at high temperatures in both p-type and n-type PbSe, similar to that found in PbTe. While the p-type lead chalcogenides (PbSe and PbTe) benefit from the high valley degeneracy (12 or more at high temperature) of the valence band, the n-type versions are limited to a valley degeneracy of 4 in the conduction band. Yet the n-type lead chalcogenides achieve a zT nearly as high as the p-type lead chalcogenides. This effect can be attributed to the weaker electron–phonon coupling (lower Deformation Potential coefficient) in the conduction band as compared with that in the valence band, which leads to higher mobility of electrons compared to that of holes. This study of PbSe illustrates the importance of the Deformation Potential coefficient of the charge-carrying band as one of several key parameters to consider for band structure engineering and the search for high performance thermoelectric materials.
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low effective mass leading to high thermoelectric performance
arXiv: Materials Science, 2011Co-Authors: Aaron D. Lalonde, Heng Wang, Jeffrey G SnyderAbstract:High Seebeck coefficient by creating large density of state (DOS) around the Fermi level through either electronic structure modification or manipulating nanostructures, is commonly considered as a route to advanced thermoelectrics. However, large density of state due to flat bands leads to large effective mass, which results in a simultaneous decrease of mobility. In fact, the net effect of high effective mass is a lower thermoelectric figure of merit when the carriers are predominantly scattered by acoustic phonons according to the Deformation Potential theory of Bardeen-Shockley. We demonstrate the beneficial effect of light effective mass leading to high power factor in n-type thermoelectric PbTe, where doping and temperature can be used to tune the effective mass. This clear demonstration of the Deformation Potential theory to thermoelectrics shows that the guiding principle for band structure engineering should be low effective mass along the transport direction.
Hongbo Zhao - One of the best experts on this subject based on the ideXlab platform.
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intrinsic carrier mobility of a single layer graphene covalently bonded with single walled carbon nanotubes
Journal of Applied Physics, 2014Co-Authors: Zhigang Shao, Qing Hao, Hongbo ZhaoAbstract:We report intrinsic carrier mobility calculations of a two-dimensional nanostructure that consists of porous single layer graphene covalently bonded with single-walled carbon nanotubes on both sides. We used first-principles calculation and found that the Deformation Potential of such system is about 25% of that of graphene, and the carrier mobility is about 5 × 104 cm2 V−1 s−1 for both electrons and holes, about one order of magnitude lower than that of graphene. This nanostructure and its three-dimensional stacking could serve as novel organic electronic materials.
Heng Wang - One of the best experts on this subject based on the ideXlab platform.
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low electron scattering Potentials in high performancemg_2si_ 0 45 sn_ 0 55 based thermoelectric solid solutions with band convergence
Advanced Energy Materials, 2013Co-Authors: Xiaohua Liu, Jeffrey G Snyder, Heng Wang, Tiejun Zhu, Hanhui Xie, Guangyu Jiang, Xinbing ZhaoAbstract:Understanding the electron and phonon transport characteristics is crucial for designing and developing high performance thermoelectric materials. Weak scattering effects on charge carriers, characterized by Deformation Potential and alloy scattering Potential, are favorable for thermoelectric solid solutions to enable high carrier mobility and thereby promising thermoelectric performance. Mg_2(Si,Sn) solid solutions have attracted much attention due to their low cost and environmental compatibility. Usually, their high thermoelectric performance with ZT ∼ 1 is ascribed to the band convergence and reduced lattice thermal conductivity caused by alloying. In this work, both a low Deformation Potential Ξ = 13 eV and a low alloy scattering Potential U = 0.7 eV are found for the thermoelectric alloys by characterizing and modeling of thermoelectric transport properties. The band convergence is also verified by the increased density-of-states effective mass. It is proposed that, in addition to band convergence and reduced lattice thermal conductivity, the low Deformation Potential and alloy scattering Potential are additional intrinsic features that contribute to the high thermoelectric performance of the solid solutions.
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low effective mass leading to high thermoelectric performance
Energy and Environmental Science, 2012Co-Authors: Aaron D. Lalonde, Heng Wang, Jeffrey G SnyderAbstract:High Seebeck coefficient by creating large density-of-states effective mass through either electronic structure modification or manipulating nanostructures is commonly considered as a route to advanced thermoelectrics. However, large density-of-state due to flat bands leads to large transport effective mass, which results in a simultaneous decrease of mobility. In fact, the net effect of such a high effective mass is a lower thermoelectric figure of merit, zT, when the carriers are predominantly scattered by phonons according to the Deformation Potential theory of Bardeen–Shockley. We demonstrate that the beneficial effect of light effective mass contributes to high zT in n-type thermoelectric PbTe, where doping and temperature can be used to tune the effective mass. This clear demonstration of the Deformation Potential theory to thermoelectrics shows that the guiding principle for band structure engineering should be low effective mass along the transport direction.
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weak electron phonon coupling contributing to high thermoelectric performance in n type pbse
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Heng Wang, Aaron D. Lalonde, Yanzhong Pei, Jeffrey G SnyderAbstract:PbSe is a surprisingly good thermoelectric material due, in part, to its low thermal conductivity that had been overestimated in earlier measurements. The thermoelectric figure of merit, zT, can exceed 1 at high temperatures in both p-type and n-type PbSe, similar to that found in PbTe. While the p-type lead chalcogenides (PbSe and PbTe) benefit from the high valley degeneracy (12 or more at high temperature) of the valence band, the n-type versions are limited to a valley degeneracy of 4 in the conduction band. Yet the n-type lead chalcogenides achieve a zT nearly as high as the p-type lead chalcogenides. This effect can be attributed to the weaker electron–phonon coupling (lower Deformation Potential coefficient) in the conduction band as compared with that in the valence band, which leads to higher mobility of electrons compared to that of holes. This study of PbSe illustrates the importance of the Deformation Potential coefficient of the charge-carrying band as one of several key parameters to consider for band structure engineering and the search for high performance thermoelectric materials.
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low effective mass leading to high thermoelectric performance
arXiv: Materials Science, 2011Co-Authors: Aaron D. Lalonde, Heng Wang, Jeffrey G SnyderAbstract:High Seebeck coefficient by creating large density of state (DOS) around the Fermi level through either electronic structure modification or manipulating nanostructures, is commonly considered as a route to advanced thermoelectrics. However, large density of state due to flat bands leads to large effective mass, which results in a simultaneous decrease of mobility. In fact, the net effect of high effective mass is a lower thermoelectric figure of merit when the carriers are predominantly scattered by acoustic phonons according to the Deformation Potential theory of Bardeen-Shockley. We demonstrate the beneficial effect of light effective mass leading to high power factor in n-type thermoelectric PbTe, where doping and temperature can be used to tune the effective mass. This clear demonstration of the Deformation Potential theory to thermoelectrics shows that the guiding principle for band structure engineering should be low effective mass along the transport direction.
Zhigang Shuai - One of the best experts on this subject based on the ideXlab platform.
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first principles predictions of thermoelectric figure of merit for organic materials Deformation Potential approximation
Journal of Chemical Theory and Computation, 2012Co-Authors: Jianming Chen, Dong Wang, Zhigang ShuaiAbstract:We propose a combined computational scheme to predict the thermoelectric properties of organic semiconductors, taking α-form phthalocyanine crystals H2Pc, CuPc, NiPc, and TiOPc as examples. This completely parameter-free approach combines first-principles band structure calculations, Boltzmann transport theory, Deformation Potential theory for electron–phonon coupling, and nonequilibrium molecular dynamics for heat transport. We abandon the constant relaxation time approximation commonly practiced in the literature. Instead, we calculate it from first principles with the Deformation Potential approximation. The obtained Seebeck coefficients are in good agreement with experimental results, validating our treatment for relaxation time. From the calculated thermoelectric figure of merit (ZT) value, we show that phthalocyanine crystals could be excellent thermoelectric materials when n-doped, with the highest ZT value of 2.5 in NiPc at a doping level of −1.5 × 1020 cm–3.
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Deformation Potential Theory
SpringerBriefs in Molecular Science, 2012Co-Authors: Zhigang Shuai, Linjun Wang, Chenchen SongAbstract:When the electron–phonon coupling is weak compared with the intermolecular electronic couplings, charge transport can be described by the band mechanism. Namely, the charge moves coherently in a wavelike manner and is scattered by phonon. In this chapter, we introduce the Deformation Potential theory, which is actually a band model including only the lattice scatterings by the acoustic Deformation Potential. It is based on the Boltzmann transport equation and sometimes, can be simplified using the effective mass approximation. Contrary to Chap. 3, where only optical phonons are considered, the acoustic phonons are the focus of this chapter. This approach is applied to a typical molecular crystal, naphthalene, and covalently bonded functional materials, graphene and graphdiyne sheets and nanoribbons.
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theoretical predictions of size dependent carrier mobility and polarity in graphene
Journal of the American Chemical Society, 2009Co-Authors: Mengqiu Long, Ling Tang, Dong Wang, Linjun Wang, Zhigang ShuaiAbstract:First-principles density functional theory coupled with Deformation Potential calculations indicate a strong width-dependent carrier mobility: for an armchair graphene ribbon whose width (i.e., num...
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the role of acoustic phonon scattering in charge transport in organic semiconductors a first principles Deformation Potential study
Science China-chemistry, 2009Co-Authors: Ling Tang, Mengqiu Long, Dong Wang, Zhigang ShuaiAbstract:The electron-acoustic phonon scattering for charge transport in organic semiconductors has been studied by first-principles density functional theory and the Boltzmann transport equation with relaxation time approximation. Within the framework of Deformation-Potential theory, the electron-longitudinal acoustic phonon scattering probability and the corresponding relaxation time have been obtained for oligoacene single crystals (naphthalene, anthracene, tetracene and pentacene). Previously, the electron-optic phonon scattering mechanism has been investigated through Holstein-Peierls model coupled with DFT calculations for naphthalene. Numerical results indicate that the acoustic phonon scattering intensity is about 3 times as large as that for the optic phonon and the obtained mobility is in much better agreement with the result of the experiment done for ultrapure single crystals. It is thus concluded that for closely packed molecular crystal where the electron is partly delocalized, acoustic phonon scattering mechanism prevails in the charge transport. Moreover, it is found that the intrinsic electron mobility is even larger than hole mobility. A frontier orbital overlap analysis can well rationalize such behavior.
Aaron D. Lalonde - One of the best experts on this subject based on the ideXlab platform.
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low effective mass leading to high thermoelectric performance
Energy and Environmental Science, 2012Co-Authors: Aaron D. Lalonde, Heng Wang, Jeffrey G SnyderAbstract:High Seebeck coefficient by creating large density-of-states effective mass through either electronic structure modification or manipulating nanostructures is commonly considered as a route to advanced thermoelectrics. However, large density-of-state due to flat bands leads to large transport effective mass, which results in a simultaneous decrease of mobility. In fact, the net effect of such a high effective mass is a lower thermoelectric figure of merit, zT, when the carriers are predominantly scattered by phonons according to the Deformation Potential theory of Bardeen–Shockley. We demonstrate that the beneficial effect of light effective mass contributes to high zT in n-type thermoelectric PbTe, where doping and temperature can be used to tune the effective mass. This clear demonstration of the Deformation Potential theory to thermoelectrics shows that the guiding principle for band structure engineering should be low effective mass along the transport direction.
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weak electron phonon coupling contributing to high thermoelectric performance in n type pbse
Proceedings of the National Academy of Sciences of the United States of America, 2012Co-Authors: Heng Wang, Aaron D. Lalonde, Yanzhong Pei, Jeffrey G SnyderAbstract:PbSe is a surprisingly good thermoelectric material due, in part, to its low thermal conductivity that had been overestimated in earlier measurements. The thermoelectric figure of merit, zT, can exceed 1 at high temperatures in both p-type and n-type PbSe, similar to that found in PbTe. While the p-type lead chalcogenides (PbSe and PbTe) benefit from the high valley degeneracy (12 or more at high temperature) of the valence band, the n-type versions are limited to a valley degeneracy of 4 in the conduction band. Yet the n-type lead chalcogenides achieve a zT nearly as high as the p-type lead chalcogenides. This effect can be attributed to the weaker electron–phonon coupling (lower Deformation Potential coefficient) in the conduction band as compared with that in the valence band, which leads to higher mobility of electrons compared to that of holes. This study of PbSe illustrates the importance of the Deformation Potential coefficient of the charge-carrying band as one of several key parameters to consider for band structure engineering and the search for high performance thermoelectric materials.
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low effective mass leading to high thermoelectric performance
arXiv: Materials Science, 2011Co-Authors: Aaron D. Lalonde, Heng Wang, Jeffrey G SnyderAbstract:High Seebeck coefficient by creating large density of state (DOS) around the Fermi level through either electronic structure modification or manipulating nanostructures, is commonly considered as a route to advanced thermoelectrics. However, large density of state due to flat bands leads to large effective mass, which results in a simultaneous decrease of mobility. In fact, the net effect of high effective mass is a lower thermoelectric figure of merit when the carriers are predominantly scattered by acoustic phonons according to the Deformation Potential theory of Bardeen-Shockley. We demonstrate the beneficial effect of light effective mass leading to high power factor in n-type thermoelectric PbTe, where doping and temperature can be used to tune the effective mass. This clear demonstration of the Deformation Potential theory to thermoelectrics shows that the guiding principle for band structure engineering should be low effective mass along the transport direction.