Markov Maxime, Hu Xixiao, Liu Han-Chun, Liu Naiming, Poon S Joseph, Esfarjani Keivan, Zebarjadi Mona
Department of Electrical and Computer Engineering, University of Virginia, Charlottesville, Virginia, 22904, USA.
Department of Physics, University of Virginia, Charlottesville, Virginia, 22904, USA.
Sci Rep. 2018 Jun 29;8(1):9876. doi: 10.1038/s41598-018-28043-3.
The best thermoelectric materials are believed to be heavily doped semiconductors. The presence of a band gap is assumed to be essential to achieve large thermoelectric power factor and figure of merit. In this work, we propose semi-metals with large asymmetry between conduction and valence bands as an alternative class of thermoelectric materials. To illustrate the idea, we study semi-metallic HgTe in details experimentally and theoretically. We employ ab initio calculations with hybrid exchange-correlation functional to accurately describe the electronic band structure in conjunction with the Boltzmann Transport theory to investigate the electronic transport properties. We calculate the lattice thermal conductivity using first principles calculations and evaluate the overall figure of merit. To validate our theoretical approach, we prepare semi-metallic HgTe samples and characterize their transport properties. Our first-principles calculations agree well with the experimental data. We show that intrinsic HgTe, a semimetal with large disparity in its electron and hole masses, has a high thermoelectric power factor that is comparable to the best known thermoelectric materials. Finally, we propose other possible materials with similar band structures as potential candidates for thermoelectric applications.
人们认为最好的热电材料是重掺杂半导体。带隙的存在被认为是实现大热电功率因子和优值的关键。在这项工作中，我们提出将导带和价带之间具有大不对称性的半金属作为一类替代的热电材料。为了说明这一想法，我们对半金属HgTe进行了详细的实验和理论研究。我们采用含杂化交换关联泛函的第一性原理计算来精确描述电子能带结构，并结合玻尔兹曼输运理论来研究电子输运性质。我们使用第一性原理计算来计算晶格热导率，并评估整体优值。为了验证我们的理论方法，我们制备了半金属HgTe样品并表征了它们的输运性质。我们的第一性原理计算与实验数据吻合得很好。我们表明，本征HgTe，一种电子和空穴质量差异很大的半金属，具有与最知名的热电材料相当的高热电功率因子。最后，我们提出了其他具有相似能带结构的可能材料作为热电应用的潜在候选材料。
