The N-type Pb-doped single crystal SnSe thermoelectric material synthesized by a Sn-flux method

Abstract

In order to execute assembly of TE modules, it is necessary to synthesize high-performance n-type SnSe. In this study, Pb element as a dopant to synthesize SnSe single crystal successfully via a facile Sn-flux route. For the larger atomic radius of Pb, the SnSe antisite defects are restrained and hence induce more Se vacancy (VSe) in the larger content Pb-doped SnSe, which makes the system n-type conduction. For the transition of majority carriers from hole to electron, the carrier concentration decreased from 4.2 × 1017cm−3 in p-type SnSe to 3.3 × 1017cm−3 in p-type Sn0.85+5Pb0.15Se and then increased to 4.1 × 1017cm−3 in n-type Sn0.1+5Pb0.9Se. A maximum power factor of 1.2 μW cm−1·K−1is obtained at room temperature. The density functional theory shows that due to the stronger metallicity of Pb, the electrons become delocalized around Sn atom, suggesting a much higher degree of electron delocalization in the Pb doped SnSe, thus it can facilitate n-type conduction.