Thermoelectric materials can realize the direct conversion between heat and electricity, which provides a new strategy for waste heat treatment and power generation. The dimensionless value ZT determines the efficiency of the device. Here, we report a record ZT maximum of about 6.96 at 700 K by performing first-principles calculations on penta-Bi2X (X = Ge, Sn) monolayers. We verified the stability of all systems and calculated the thermoelectric transport properties. The multiband energy degeneracy leads to large Seebeck coefficients, while the small phonon group velocity and strong anharmonic phonon scattering result in ultra-low thermal conductivity. Thus, in both systems, the higher ZT values are found. The high performance of Bi2Ge and Bi2Sn monolayers provide a new guidance for finding layered thermoelectric materials.

中文翻译：

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Bi2X （X = Ge， Sn） 单层：具有超低导热率的有前途的热电材料


热电材料可以实现热电之间的直接转换，为余热处理和发电提供了新的策略。无量纲值 ZT 决定了设备的效率。在这里，我们通过对 penta-Bi2X （X = Ge， Sn） 单层进行第一性原理计算，在 700 K 时报告了创纪录的 ZT 最大值约为 6.96。我们验证了所有系统的稳定性并计算了热电输运特性。多频段能量简并导致较大的塞贝克系数，而较小的声子群速度和强的非谐波声子散射导致超低的热导率。因此，在这两个系统中，都发现了更高的 ZT 值。Bi2Ge 和 Bi2Sn 单层膜的高性能为寻找层状热电材料提供了新的指导。