Wang Si, Su Xianli, Bailey Trevor P, Hu Tiezheng, Zhang Zhengkai, Tan Gangjian, Yan Yonggao, Liu Wei, Uher Ctirad, Tang Xinfeng
State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology Wuhan Hubei 430070 China
Department of Physics, University of Michigan Ann Arbor MI 48109 USA
RSC Adv. 2019 Mar 1;9(13):7115-7122. doi: 10.1039/c9ra00566h.
Despite the achievable high thermoelectric properties in SnSe single crystals, the poor mechanical properties and the relatively high cost of synthesis restrict the large scale commercial application of SnSe. Herein, we reported that co-doping with Na and Ag effectively improves the thermoelectric properties of polycrystalline SnSe. Temperature-dependent carrier mobility indicates that the grain boundary scattering is the dominant scattering mechanism near room temperature, giving rise to low electrical conductivity for the polycrystalline SnSe in comparison with that of the single crystal. Co-doping with Na and Ag improves the electrical conductivity of polycrystalline SnSe with a maximum value of 90.1 S cm at 323 K in NaAgSnSe, and the electrical conductivity of the (Na, Ag) co-doped samples is higher than that of the single doped samples over the whole temperature range (300-773 K). Considering the relatively high Seebeck coefficient of 335 μV K at 673 K and the minimum thermal conductivity of 0.48 W m K at 773 K, NaAgSnSe is observed to have the highest PF and among the series of samples, with values of 0.50 mW cm K and 0.81 at 773 K, respectively. Its average PF and are 0.43 mW cm K and 0.37, which is 92% and 68% higher than that of NaSnSe, 40% and 43% higher than that of AgSnSe, and 304% and 277% higher than that of the previously reported SnSe, respectively.
尽管SnSe单晶具有可实现的高热电性能，但较差的机械性能和相对较高的合成成本限制了SnSe的大规模商业应用。在此，我们报道了Na和Ag共掺杂有效地改善了多晶SnSe的热电性能。温度依赖的载流子迁移率表明，在室温附近，晶界散射是主要的散射机制，这导致多晶SnSe的电导率比单晶低。Na和Ag共掺杂提高了多晶SnSe的电导率，在NaAgSnSe中，323 K时最大值为90.1 S cm，在整个温度范围（300 - 773 K）内，（Na，Ag）共掺杂样品的电导率高于单掺杂样品。考虑到在673 K时相对较高的塞贝克系数为335 μV K，在773 K时最小热导率为0.48 W m K，观察到NaAgSnSe在系列样品中具有最高的功率因子和优值，在773 K时分别为0.50 mW cm K和0.81。其平均功率因子和优值分别为0.43 mW cm K和0.37，分别比NaSnSe高92%和68%，比AgSnSe高40%和43%，比先前报道的SnSe高304%和277%。
