Jong Un-Gi, Kang Chung-Jin, Kim Su-Yong, Kim Hyon-Chol, Yu Chol-Jun
Chair of Computational Materials Design (CMD), Faculty of Materials Science, Kim Il Sung University, PO Box 76, Pyongyang, Democratic People's Republic of Korea.
Institute of Organic Chemistry, Faculty of Chemistry, Kim Il Sung University, PO Box 76, Pyongyang, Democratic People's Republic of Korea.
Phys Chem Chem Phys. 2022 Mar 2;24(9):5729-5737. doi: 10.1039/d1cp05796k.
Tailoring novel thermoelectric materials (TEMs) with a high efficiency is challenging due to the difficulty in realizing both low thermal conductivity and high thermopower factor. In this work, we propose ternary chalcogenides CsAgQ (Q = Te, Se) as promising TEMs based on first-principles calculations of their thermoelectric properties. Using lattice dynamics calculations within self-consistent phonon theory, we predict their ultralow lattice thermal conductivities below 0.27 W m K, revealing the strong lattice anharmonicity and rattling vibrations of Ag atoms as the main origination. By using the mBJ exchange-correlation functional, we calculate the electronic structures with the direct band gaps in good agreement with experiments, and evaluate the charge carrier lifetime as a function of temperature within the deformation potential theory. Our calculations to solve Boltzmann transport equations demonstrate high thermopower factors of 2.5 mW m K upon p-type doping at 300 K, comparable to the conventional dichalcogenide thermoelectric GeTe. With these ultralow thermal conductivities and high thermopower factors, we determine a relatively high thermoelectric figure of merit along the -axis, finding the maximum value of to be 2.5 at 700 K for CsAgSe by optimizing the hole concentration. Our computational results highlight the great potentiality of CsAgQ (Q = Te, Se) for high-performance thermoelectric devices operating at room temperature.
由于难以同时实现低热导率和高热电优值因子，定制高效的新型热电材料（TEMs）具有挑战性。在这项工作中，我们基于对其热电性能的第一性原理计算，提出三元硫族化物CsAgQ（Q = Te，Se）作为有前景的TEMs。利用自洽声子理论中的晶格动力学计算，我们预测它们的超低晶格热导率低于0.27 W m⁻¹K⁻¹，揭示了Ag原子强烈的晶格非谐性和晃动振动是主要来源。通过使用mBJ交换关联泛函，我们计算出与实验结果吻合良好的直接带隙电子结构，并在形变势理论内评估电荷载流子寿命随温度的变化。我们求解玻尔兹曼输运方程的计算表明，在300 K下进行p型掺杂时，热电优值因子高达2.5 mW m⁻¹K⁻²，与传统的二硫族化物热电材料GeTe相当。凭借这些超低的热导率和高热电优值因子，我们确定了沿c轴相对较高的热电优值，通过优化空穴浓度，发现CsAgSe在700 K时的最大值为2.5。我们的计算结果突出了CsAgQ（Q = Te，Se）在室温下运行的高性能热电装置方面的巨大潜力。
