Anisotropic thermoelectric transport properties in polycrystalline SnSe2 * *Project supported by the Beijing Natural Science Foundation, China (Grant No. JQ18004), the National Key Research and Development Program of China (Grant Nos. 2018YFA0702100 and 2018YFB0703600), the National Natural Science Foundation of China (Grant No. 51772012), Shenzhen Peacock Plan Team (Grant No. KQTD2016022619565991), and 111 Project (Grant No. B17002). This work was

Abstract

It is reported that SnSe2 consisting of the same elements as SnSe, is a new promising thermoelectric material with advantageous layered structure. In this work, the thermoelectric performance of polycrystalline SnSe2 is improved through introducing SnSe phase and electron doping (Cl doped in Se sites). The anisotropic transport properties of SnSe2 are investigated. A great reduction of the thermal conductivity is achieved in SnSe2 through introducing SnSe phase, which mainly results from the strong SnSe2–SnSe inter-phase scattering. Then the carrier concentration is optimized via Cl doping, leading to a great enhancement of the electrical transport properties, thus an extraordinary power factor of ∼5.12 μW⋅cm−1⋅K−2 is achieved along the direction parallel to the spark plasma sintering (SPS) pressure direction (∥ P). Through the comprehensive consideration on the anisotropic thermoelectric transport properties, an enhanced figure of merit ZT is attained and reaches to ∼ 0.6 at 773 K in SnSe2-2% SnSe after 5% Cl doping along the ∥ P direction, which is much higher than ∼ 0.13 and ∼ 0.09 obtained in SnSe2-2% SnSe and pristine SnSe2 samples, respectively.