功勋
塞贝克系数
凝聚态物理
热电效应
热导率
材料科学
热电材料
带隙
热传导
功率因数
电子能带结构
玻尔兹曼常数
工程物理
光电子学
功率(物理)
热力学
物理
复合材料
作者
Patrizio Graziosi,Zhen Li,Neophytos Neophytou
摘要
Low band gap thermoelectric materials suffer from bipolar effects at high temperatures, with increased electronic thermal conductivity and reduced Seebeck coefficient, leading to reduced power factor and low ZT figure of merit. In this work we show that the presence of strong transport asymmetries between the conduction and valence bands can allow high phonon-limited electronic conductivity at finite Seebeck coefficient values, leading to largely enhanced power factors. The power factors that can be achieved can be significantly larger compared to their maximum unipolar counterparts, allowing for doubling of the ZT figure of merit. We identify this behavior in low band gap cases from the half-Heusler materials family. Using both, advanced electronic Boltzmann transport calculations for realistic material bandstructures, as well as model parabolic electronic bands, we elaborate on the parameters that determine this effect. We then develop a series of descriptors which can guide machine learning studies in identifying such classes of materials with extraordinary power factors at nearly pristine conditions. For this we test more than 3000 analytical bandstructures and their features, and more than 120 possible descriptors, to identify the most promising ones that contain: i) only band structure features for easy identification from material databases, and ii) band structure and transport parameters that provide much higher correlations, but for which parameter availability can be somewhat scarce.
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