Thermoelectric materials can serve for conversion between thermal and electrical energy. In the search for thermoelectric materials, layered SnSe and ${\mathrm{SnSe}}_2$ are promising candidates. We have successfully synthesized SnSe and ${\mathrm{SnSe}}_2$ single crystals by the modified Bridgman method and studied their thermoelectric properties: thermopower $\left(S\right)$, thermal conductivity $\left(\kappa \right)$, and electrical conductivity $(\sigma )$ in the temperature range between 2 and 400 K, which are absent in the literature. The kink observed in the thermopower corresponds to the metallic-nonmetallic crossover temperature for both SnSe and ${\mathrm{SnSe}}_2$, reflecting their inherent electronic nature. Compared with ${\mathrm{SnSe}}_2$, >100 K, we find that SnSe exhibits higher electrical conductivity, higher thermopower, and lower thermal conductivity, thus resulting in the higher figure of merit. Hall effect measurements reveal that the Hall mobility in SnSe is an order higher than that in ${\mathrm{SnSe}}_2$, advancing its thermoelectric performance. These experimental results are supported by first-principles calculations, which indicate that the inequivalent Sn-Se bonding lengths help improve the figure of merit of SnSe.

中文翻译：

---

SnSe和SnSe2单晶的热电性能

热电材料可以用于热能和电能之间的转换。在寻找热电材料时，层状 SnSe 和${\mathrm{硒化锡}}_2$都是有前途的候选人。我们已经成功合成了 SnSe 和${\mathrm{硒化锡}}_2$通过改进的布里奇曼方法制备单晶并研究其热电特性：热电$（S）$， 导热系数$（\kappa ）$和电导率$（\sigma ）$温度范围在 2 到 400 K 之间，这在文献中是不存在的。热电势中观察到的扭结对应于 SnSe 和 SnSe 的金属-非金属交叉温度${\mathrm{硒化锡}}_2$，反映了它们固有的电子性质。和....相比${\mathrm{硒化锡}}_2$，>100 K，我们发现 SnSe 表现出更高的电导率、更高的热电势和更低的热导率，从而导致更高的品质因数。霍尔效应测量表明 SnSe 中的霍尔迁移率比${\mathrm{硒化锡}}_2$，提高其热电性能。这些实验结果得到了第一性原理计算的支持，表明不等的 Sn-Se 键合长度有助于提高 SnSe 的品质因数。