Prof. JIANG Jun’s team at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of Chinese Academy of Sciences (CAS) reported excellent thermoelectric performance along the out-of-plane direction of n-type tin selenide (SnSe) single crystals by alloying with PbBr2. The study revealed that the thermoelectric performance of n-type SnSe along the out-of-plane direction is very sensitive to the lattice parameter a, owing to the Fermi surface dynamics. The study has been published in Energy & Environmental Science(Energy Environ. Sci.).
Thermoelectric materials offer a unique solution for the issues of energy and the environment, thanks to their ability in the direct conversion from waste heat into electricity. Recently, the layered chalcogenide SnSe has attracted great interest owing to its remarkable thermoelectric performance as well as the traits of being resource-rich and environment-friendly.
The research group successfully fabricated PbBr2-doped SnSe single crystals by a temperature gradient method. In contrast to the p-type SnSe, the n-type SnSe was found prefer the out-of-plane direction, achieving the maximum ZT of 2.1 at 770 K. Interestingly, a sharp drop of the carrier mobility was observed at a doping level of x = 3%. Combined with theoretical calculations, the X-ray diffraction (XRD) measurements indicated that the Fermi surface dynamics driven by the lattice variation is the underlying reason. By introducing Ge doping, the lattice parameter a in x = 3% was decreased, resulting in the greatly enhanced carrier mobility and the maximum ZT of 1.7.
The study revealed that the thermoelectric performance of n-type SnSe is driven by the subtle structures of the Fermi surface, thus the Fermi surface dynamics plays a crucial role in the thermoelectric performance optimization. In addition, it has provided a new perspective for the investigation of thermoelectric materials with layered structures.
This work was supported by the National Natural Science Foundation of China (No. 51872301, No. 21875273 and No. 51702334), Zhejiang Provincial Science Foundation for Distinguished Young Scholars (No. LR16E020001), Natural Science Foundation of Zhejiang Province (No. LY17E020013, No. LY18A040008 and No. LY18E020017), and Youth Innovation Promotion Association of CAS (No. 2019298).
Fig. Fermi-surface dynamics and improved thermoelectric performance in PbBr2-doped SnSe0.95 (Image by NIMTE)
Contact
TAN Xiaojian
Ningbo Institute of Materials Technology and Engineering
E-mail: tanxiaojian@nimte.ac.cn