Cagnoni Matteo, Führen Daniel, Wuttig Matthias
I. Institute of Physics (IA), RWTH Aachen University, 52056, Aachen, Germany.
JARA-FIT Institute Green-IT, RWTH Aachen University and Forschungszentrum Jülich, 52056, Aachen, Germany.
Adv Mater. 2018 Jul 5:e1801787. doi: 10.1002/adma.201801787.
Thermoelectric materials provide a challenge for materials design, since they require optimization of apparently conflicting properties. The resulting complexity has favored trial-and-error approaches over the development of simple and predictive design rules. In this work, the thermoelectric performance of IV-VI chalcogenides on the tie line between GeSe and GeTe is investigated. From a combination of optical reflectivity and electrical transport measurements, it is experimentally proved that the outstanding performance of IV-VI compounds with octahedral-like coordination is due to the anisotropy of the effective mass tensor of the relevant charge carriers. Such an anisotropy enables the simultaneous realization of high Seebeck coefficients, due to a large density-of-states effective mass, and high electrical conductivity, caused by a small conductivity effective mass. This behavior is associated to a unique bonding mechanism by means of a tight-binding model, which relates band structure and bond energies; tuning the latter enables tailoring of the effective mass tensor. The model thus provides atomistic design rules for thermoelectric chalcogenides.
热电材料给材料设计带来了挑战，因为它们需要优化一些明显相互冲突的特性。由此产生的复杂性使得试错法比简单且具有预测性的设计规则的开发更受青睐。在这项工作中，研究了位于GeSe和GeTe之间连线上的IV-VI族硫族化物的热电性能。通过光学反射率和电输运测量的结合，实验证明具有八面体状配位的IV-VI族化合物的优异性能归因于相关电荷载流子有效质量张量的各向异性。这种各向异性使得由于态密度有效质量大而能同时实现高塞贝克系数，并且由于电导率有效质量小而能实现高电导率。这种行为通过一个紧束缚模型与一种独特的键合机制相关联，该模型将能带结构和键能联系起来；调整键能能够定制有效质量张量。因此，该模型为热电硫族化物提供了原子级的设计规则。
