The thermoelectric conversion efficiency of a material relies on a dimensionless parameter (ZT = S 2 σT/κ). It is a great challenge in enhancing the ZT value basically due to that the related transport factors of most of the bulk materials are inter-conditioned to each other, making it very difficult to simultaneously optimize these parameters. In this report, the negative correlation between power factor and thermal conductivity of nano-scaled SnS2 multilayers is predicted by high-level first-principle computations combined with Boltzmann transport theory. By diminishing the thickness of SnS2 nanosheet to about 3 L, the S and σ along a direction simultaneously increase whereas κ decreases, achieving a high ZT value of 1.87 at 800 K. The microscopic mechanisms for this unusual negative correlation in nano-scaled two dimensional (2D) material are elucidated and attributed to the quantum confinement effect. The results may open a way to explore the high ZT thermoelectric nano-devices for the practical thermoelectric applications.
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机译：材料的热电转换效率取决于无量纲参数（ZT = S 2 σT/κ）。基本上由于大多数散装物料的相关运输因子相互调节，这对提高ZT值是一个巨大的挑战，这使得同时优化这些参数非常困难。在本报告中，通过高级第一性原理计算与玻尔兹曼输运理论相结合，预测了纳米级SnS2多层薄膜的功率因数与导热系数之间的负相关关系。通过将SnS2纳米片的厚度减小到约3 L，沿方向的S和σ同时增加，而κ减小，从而在800 K时达到1.87的高ZT值。阐明了（2D）材料，并将其归因于量子约束效应。结果可能为探索用于实际热电应用的高ZT热电纳米器件开辟道路。
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