The Role of Electronic Bandstructure Shape in Improving the Thermoelectric Power Factor of Complex Materials
The Role of Electronic Bandstructure Shape in Improving the Thermoelectric Power Factor of Complex Materials
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DOI：
10.1021/acsaelm.3c00887
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发表时间：
2023-11
影响因子：
4.7
通讯作者：
P. Graziosi;N. Neophytou
中科院分区：
文献类型：
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作者：
P. Graziosi;N. Neophytou
种类繁多的复杂电子结构材料及其合金为改善热电功率因数(PF)提供了非常有前途的方向。它们的电子结构包含丰富的特征，被称为“表面复杂性”，其中之一是高度各向异性的翘曲能量表面形状，在某些情况下具有拉长的特征和线条。在这项工作中，我们使用玻耳兹曼输运模拟来量化电子结构能面的形状对PF的影响。使用解析椭球带，以及来自Half-Heusler群的真实带，我们表明，在实际情况下，仅带形复杂性就可以提供~3x的PF优势。然而，各向异性散射机制的存在，如电离杂质或极性光学声子散射，可以使这些改善降低高达50%。结果表明，基于态密度与电导有效质量mDOS/MC的简单比值，再加上谷数，就可以捕捉到中等到高度关联的各向异性形状。为此，我们使用了一种方便的方法来提取这些质量，通过将材料的复杂能带结构映射到抛物线电子结构，而不需要玻尔兹曼输运代码。尽管Pf依赖于许多参数，但仅关于能带形状的益处的信息对于识别和理解新型热电材料的性能将非常有用。
The large variety of complex electronic structure materials and their alloys, offer highly promising directions for improvements in thermoelectric (TE) power factors (PF). Their electronic structure contains rich features, referred to as 'surface complexity', one of them being the highly anisotropic warped energy surface shapes with elongated features and threads in some cases. In this work we use Boltzmann transport simulations to quantify the influence that the shape of the electronic structure energy surfaces has on the PF. Using both analytical ellipsoidal bands, as well as realistic bands from the group of half-Heuslers, we show that band shape complexity alone can offer an advantage to the PF of ~3x in realistic cases. The presence of anisotropic scattering mechanisms such as ionized impurity or polar optical phonon scattering, however, can reduce these improvements by up to ~50%. We show that expressions based on the simple ratio of the density-of-states to the conductivity effective masses, mDOS/mC, together with the number of valleys, can capture the anisotropy shape with a moderate to high degree of correlation. For this, we use a convenient way to extract these masses by mapping the complex bandstructures of materials to parabolic electronic structures, without the need for Boltzmann transport codes. Despite the fact that the PF depends on many parameters, information about the benefits of the band shape alone, would be very useful for identifying and understanding the performance of novel thermoelectric materials.