SnSe织构化多晶电声输运调控及热电性能优化

The recently reported ZT value of SnSe single crystal reached 2.6, which is the highest value among those of the bulk thermoelectric materials. The single crystal of SnSe has poor mechanical properties, and requires very strict growth conditions. Polycrystalline material is regarded to overcome these difficulties, but the corresponding ZT value is much lower. It is of great significance to understand the difference of electron/phonon transport mechanism between single crystal and polycrystal, and carry out practical methods to improve the thermoelectric performance of the latter. This proposal will be implemented by closely combining theoretical and experimental methods. We will focus on the stable and controllable preparation of p-type and n-type SnSe textured polycrystal firstly. Then, we will find the proper doping elements via molecular dynamics simulation and band engineering design, and enhance the power factor by optimizing the process scheme according to the phase diagram. Based on the first-principles calculation of phonon transport, we will introduce targeted multi-scale scattering centers to significantly reduce the thermal conductivity of polycrystalline SnSe, and realize the “electron-transmitting/phonon-blocking” effect. The aim of this research is to provide theoretical and experimental insights into the development of SnSe-based materials with high thermoelectric performance.

SnSe单晶是当前报道性能最佳的块体热电材料；SnSe多晶可克服单晶制备条件苛刻、机械性能差等缺点，但其热电性能尚存在很大差距。深刻理解SnSe单晶与多晶电声输运差异的内在机制，明确改善多晶热电性能的具体措施，这是当前亟待解决的重要问题。本项目拟将理论与实验紧密结合：1）探索p型/n型SnSe织构化多晶稳定可控制备工艺；2）通过分子动力学模拟以及能带工程设计，为优选有效掺杂元素提供依据，并结合相图分析改进制备方案，以充分提高SnSe电学性能；3）基于第一性原理声子输运计算，有针对性地引入多尺度特征频率散射中心，显著降低SnSe多晶热导率。最终凸显“电子通透/声子阻隔”效应，充分改善热电性能。本项目实施对于发展SnSe等新型高效热电材料具有重要意义。

SnSe单晶是当前报道性能最佳的块体热电材料；SnSe多晶可克服单晶制备条件苛刻、机械性能差等缺点，但其热电性能尚存在很大差距。深刻理解SnSe单晶与多晶电声输运差异的内在机制，明确改善多晶热电性能的具体措施，这是当前亟待解决的重要问题。本项目通过理论与实验紧密结合，探索了液相烧结和液相热挤压烧结等新型工艺提高p型SnSe多晶织构度从而优化其热电性能；提出了费米面动力学策略实现了n型SnSe单晶面外方向“电子通透/声子阻隔”效应，将最优化ZT值提升至2.1；探索了一系列n型掺杂剂，并选用NbCl5掺杂和位错工程同时提升了n型SnSe多晶的热电性能和力学性能；此外，还提出了自旋轨道耦合效应优化立方相SnSe的新方案，为SnSe材料的实际应用提供了新思路。本项目实施对于发展SnSe等新型高效热电材料具有重要意义。