Title: Thermoelectric properties of orthorhombic group IV-VI monolayers from the first-principles calculations Show Chinese title

Title: 四族-六族正交单层材料的热电性质的第一性原理计算

Abstract: Two-dimensional (2D) materials may have potential applications in thermoelectric devices. In this work, we systematically investigate the thermoelectric properties of orthorhombic group IV-VI monolayers $\mathrm{AB}$ (A=Ge and Sn; B=S and Se) by the first-principles calculations and semiclassical Boltzmann transport theory. The spin-orbit coupling (SOC) is included to investigate their electronic transport, which produces observable effects on power factor, especially for n-type doping. According to calculated $ZT$, the four monolayers exhibit diverse anisotropic thermoelectric properties, although they have similar hinge-like crystal structure. The GeS along zigzag and armchair directions shows the strongest anisotropy, while SnS and SnSe show mostly isotropic efficiency of thermoelectric conversion, which can be understood by the strength of anisotropy of their respective power factor, electronic and lattice thermal conductivities. Calculated results show that $ZT$ for different carriers of n- and p-type has little difference for GeS, SnS and SnSe. It is found that GeSe, SnS and SnSe show better thermoelectric performance compared to GeS in n-type doping, and SnS and SnSe exhibit higher efficiency of thermoelectric conversion in p-type doping. Compared to a lot of 2D materials, orthorhombic group IV-VI monolayers $\mathrm{AB}$ (A=Ge and Sn; B=S and Se) may possess better thermoelectric performance due to higher power factor and lower thermal conductivity. Our work would be beneficial to further experimental study. Show Chinese abstract

Abstract: 二维（2D）材料可能在热电设备中有潜在应用。 在本工作中，我们通过第一性原理计算和半经典玻尔兹曼输运理论系统地研究了正交晶系IV-VI族单层材料$\mathrm{AB}$ （A=Ge和Sn；B=S和Se）的热电性能。 包括自旋-轨道耦合（SOC）以研究其电子输运，这对其功率因数产生了可观察的影响，尤其是在n型掺杂的情况下。 根据计算的 $ZT$，这四种单层材料表现出不同的各向异性热电性能，尽管它们具有相似的铰链状晶体结构。 GeS在锯齿形和扶手椅方向上显示出最强的各向异性，而SnS和SnSe则表现出主要各向同性的热电转换效率，这可以通过各自功率因数、电子和晶格热导率的各向异性强度来理解。 计算结果表明，对于不同载流子的n型和p型，GeS、SnS和SnSe的$ZT$几乎没有差异。 发现与GeS相比，GeSe、SnS和SnSe在n型掺杂下表现出更好的热电性能，而在p型掺杂下，SnS和SnSe表现出更高的热电转换效率。 与许多二维材料相比，正交晶系IV-VI族单层材料 $\mathrm{AB}$ （A=Ge和Sn；B=S和Se）可能由于较高的功率因数和较低的热导率而具有更好的热电性能。 我们的工作将有助于进一步的实验研究。