Dou Wenzhen, Spooner Kieran B, Kavanagh Seán R, Zhou Miao, Scanlon David O
School of Physics, Beihang University, Beijing 100191, China.
Department of Chemistry, University College London, London WC1H 0AJ, U.K.
J Am Chem Soc. 2024 Jul 3;146(26):17679-17690. doi: 10.1021/jacs.4c01838. Epub 2024 Jun 18.
The complex interrelationships among thermoelectric parameters mean that design of high-performing materials is difficult. However, band engineering can allow the power factor to be optimized through enhancement of the Seebeck coefficient. Herein, using layered SbSiTe and ScSiTe as model systems, we comprehensively investigate and compare their thermoelectric properties by employing density functional theory combined with semiclassical Boltzmann transport theory. Our simulations reveal that SbSiTe exhibits superior electrical conductivity compared to ScSiTe due to lower scattering rates and more pronounced band dispersion. Remarkably, despite SbSiTe exhibiting a lower lattice thermal conductivity and superior electrical conductivity, ScSiTe is predicted to achieve an extraordinary dimensionless figure of merit () of 3.51 at 1000 K, which significantly surpasses the predicted maximum of 2.76 for SbSiTe at 900 K. We find the origin of this behavior to be a combined increase in band (valley) degeneracy and anisotropy upon switching the conduction band orbital character from Sb p to Sc d, yielding a significantly improved Seebeck coefficient. This work suggests that enhancing band degeneracy and anisotropy (complexity) through compositional variation is an effective strategy for improving the thermoelectric performance of layered materials.
热电参数之间复杂的相互关系意味着高性能材料的设计具有挑战性。然而，能带工程可以通过增强塞贝克系数来优化功率因数。在此，我们以层状SbSiTe和ScSiTe为模型体系，采用密度泛函理论结合半经典玻尔兹曼输运理论，全面研究并比较了它们的热电性能。我们的模拟结果表明，由于散射率较低且能带色散更为显著，SbSiTe比ScSiTe表现出更高的电导率。值得注意的是，尽管SbSiTe的晶格热导率较低且电导率较高，但预测ScSiTe在1000 K时能达到3.51的优异无量纲品质因数（ZT），这显著超过了SbSiTe在900 K时预测的最大ZT值2.76。我们发现这种现象的根源在于，当导带轨道特征从Sb p转变为Sc d时，能带（谷）简并度和各向异性共同增加，从而使塞贝克系数得到显著提高。这项工作表明，通过成分变化增强能带简并度和各向异性（复杂性）是提高层状材料热电性能的有效策略。
