The thermoelectric performance of anisotropic SnSe doped with Na

Abstract

Lead-free polycrystalline SnSe is a promising thermoelectric compound consisting of earth-abundant elements. However, the poor electrical transport property for low intrinsic defect concentration (3 × 10¹⁷ cm⁻³) limits the usage of the stoichiometric SnSe compound. In this work, Na₂Se as an acceptor was doped into SnSe in order to optimize the electrical transport properties, especially to increase the carrier concentration. As a result, the carrier concentrations increased and saturated at about 1.0 × 10¹⁹ cm⁻³ for Na_0.01Sn_0.99Se at 300 K, and a maximum power factor of 0.48 mW m⁻¹ K⁻² was obtained. A maximum zT value of 0.75 was obtained at 823 K for Na_0.01Sn_0.99Se along the direction perpendicular to the sintering pressure, which is 25% higher than that (0.6) of the undoped SnSe compound.