SnSe基单晶热电材料缺陷与费米能级位置调控的研究

缺陷特征及费米能级与热电材料电子结构、电热输运性能密切相关，然而其与热电性能的关联规律及相关物理机制尚不清楚，相关研究对热电材料性能突破至关重要，有望成为热电领域研究的前沿。本项目以SnSe单晶样品为研究对象，采用Bridgeman方法，调控其工艺参数，制备最优化、可定制化的SnSe单晶样品。系统研究工艺参数对单晶样品微结构的影响及作用机制；探索缺陷特征与材料电声输运的关联规律及相关物理机理；研究各种处理手段对费米能级附近电子结构的影响规律，调节载流子浓度。从而实现电热输运特性的“一体化”协同控制，显著提升SnSe单晶样品热电性能。该项目研究成果对阐明缺陷与费米能级特征对材料电声输运特性的影响规律具有重要科学意义，为其它材料体系热电优值的提升提供了广阔的空间与自由的途径。

Defects and Fermi level is closely related to electronic structure and transport properties of thermoelectric(TE) materials. However, this relationship so far is not clear and to ravel it is indeed important and advantageous for further enhancement of thermoelectric performance. In this project, by optimizing the synthesis parameters, we successfully fabricate high quality SnSe single crystal via Bridgeman method. We systematically study the dependence of microstructure on the fabrication procedure as well as the corresponding mechanism behind. Besides, a relationship between the defects feature and electron/phonon transport properties is also explored. Furthermore, the manipulation of Fermi level is conducted by doping, substitution and interlayer intercalation. This synergistic enhancement mechanism of thermoelectric performance in SnSe single crystal is demonstrated, leading to an improved ZT value. This work is a good example of how to enhance the TE performance of SnSe based single crystal by means of the optimization of defects and Fermi level.