Recently, one research group from CAS Center for Excellence in Superconducting Electronics of SIMIT, leaded by Prof. Dawei Shen, successfully achieved the high-resolution low-lying electronic structure of SnSe, a thermoelectric material currently maintaining the highest thermoelectric figure of merit, using the complementary angle-resolved photoemission spectroscopy and low-temperature quantum transport. In collaboration with one other group from Zhejiang University, they could further realize the effective control of thermoelectric properties of this material of SeSn through “defect engineering”. This work paves the way for the further utilization of energy-band engineering to synthesize and improve high-efficiency thermoelectric materials. This work, tilted "Defects controlled hole doping and multivalley transport in SnSe single crystals" has been published in the journal of Nature Communications on 3rd, January 2018.

This study reveals that SnSe processes the unique low-lying electronic structure with both "multivalley" bands and linear dispersion similar to graphene (Figure 1). The former can greatly enhance the Seeback coefficient of the material, and the latter would effectively enhance the conductivity of the material. Therefore, the combination of these two factors makes its thermoelectric figure of merit has been greatly enhanced. This is the first time that people can understand the unusual thermoelectric features of SnSe. On this basis, they proposed a "pudding-mould" model that can improve performance of the search for high thermoelectric material with excellent merit from the microscopic point of view. In addition, by intentionally introducing SnSe2 impurity and point dislocations, the study also realizes the effective regulation of the carrier concentration in SnSe under the premise of keeping its basic physical properties. This work opens up a new theoretical direction and technical foundation for the future synthesis and improvement of high performance thermoelectric materials by using the mature and effective means of "defect engineering".

Prof. Dawei Shen (SIMIT) and Prof. Yi Zheng ( Zhejiang University) co-supervised this project. This work is support by National Science Foundation of China (Grant number: 11227902) and some other grants.