Ultralow Thermal Conductivity, Multiband Electronic Structure and High Thermoelectric Figure of Merit in TlCuSe,Advanced Materials

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Ultralow Thermal Conductivity, Multiband Electronic Structure and High Thermoelectric Figure of Merit in TlCuSe
Advanced Materials ( IF 27.4 ) Pub Date : 2021-09-14 , DOI: 10.1002/adma.202104908
Wenwen Lin _{1,

2} , Jiangang He ₂ , Xianli Su _{1,

3} , Xiaomi Zhang ₂ , Yi Xia ₂ , Trevor P Bailey ₄ , Constantinos C Stoumpos _{1,

5} , Ganjian Tan _{1,

3} , Alexander J E Rettie _{6,

7} , Duck Young Chung ₆ , Vinayak P Dravid ₂ , Ctirad Uher ₄ , Chris Wolverton ₂ , Mercouri G Kanatzidis _{1,

2,

5}

Affiliation

The entanglement of lattice thermal conductivity, electrical conductivity, and Seebeck coefficient complicates the process of optimizing thermoelectric performance in most thermoelectric materials. Semiconductors with ultralow lattice thermal conductivities and high power factors at the same time are scarce but fundamentally interesting and practically important for energy conversion. Herein, an intrinsic p-type semiconductor TlCuSe that has an intrinsically ultralow thermal conductivity (0.25 W m⁻¹ K⁻¹), a high power factor (11.6 µW cm⁻¹ K⁻²), and a high figure of merit, ZT (1.9) at 643 K is described. The weak chemical bonds, originating from the filled antibonding orbitals p-d* within the edge-sharing CuSe₄ tetrahedra and long TlSe bonds in the PbClF-type structure, in conjunction with the large atomic mass of Tl lead to an ultralow sound velocity. Strong anharmonicity, coming from Tl⁺ lone-pair electrons, boosts phonon–phonon scattering rates and further suppresses lattice thermal conductivity. The multiband character of the valence band structure contributing to power factor enhancement benefits from the lone-pair electrons of Tl⁺ as well, which modify the orbital character of the valence bands, and pushes the valence band maximum off the Γ-point, increasing the band degeneracy. The results provide new insight on the rational design of thermoelectric materials.

中文翻译：

TlCuSe 中的超低热导率、多带电子结构和高热电性能因数

晶格热导率、电导率和塞贝克系数的纠缠使大多数热电材料的热电性能优化过程变得复杂。同时具有超低晶格热导率和高功率因数的半导体是稀缺的，但对于能量转换具有根本的意义和实际意义。在此，本征 p 型半导体 TlCuSe 具有本征超低热导率 (0.25 W m ^-1 K ^-1 )、高功率因数 (11.6 µW cm ^-1 K ^-2 ) 和高品质因数ZT描述了 643 K 下的 (1.9)。源自共享边缘 CuSe ₄四面体中的填充反键轨道 pd* 的弱化学键和PbClF 型结构中的长 Tl  Se 键，结合 Tl 的大原子质量导致超低声速。来自 Tl ⁺孤对电子的强非谐性提高了声子 - 声子散射率并进一步抑制晶格热导率。有助于功率因数增强的价带结构的多带特性也得益于 Tl ⁺的孤对电子，它改变了价带的轨道特性，并将价带最大值推离Γ-点，增加带简并性。该结果为热电材料的合理设计提供了新的见解。

更新日期：2021-11-01

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