Enhanced Thermoelectric Transport Properties of <i>n</i>-type InSe by Sn doping

Abstract

Layered post transition metal chalcogenides such as SnSe, SnSe<sub>2</sub>, In<sub>2</sub>Se<sub>3</sub>, and In<sub>4</sub>Se<sub>3</sub> have attracted attention as promising thermoelectric materials due to their intrinsically low lattice thermal conductivities. Recently, <i>n</i>-type indium selenide (InSe) based materials have also been suggested as good candidates for thermoelectric materials by optimizing their electrical properties, i.e., increasing carrier concentration. Here, we report enhancement of the thermoelectric properties of <i>n</i>-type InSe by Sn substitutional doping at the In site. A series of In<sub>1-x</sub>Sn<sub>x</sub>Se for x = 0, 0.03, 0.05, 0.15 and 0.2 was examined. The carrier concentration and electrical conductivity increased due to the Sn substitution, since Sn behaves as a shallow electron donor in InSe, while the Seebeck coefficient decreased moderately. In addition, it was found that effective mass was increased by more than 10 times by Sn doping. As a result, the power factor was enhanced from 0.07 mW/mK<sup>2</sup> to 0.13 mW/mK<sup>2</sup> at 800 K. The total thermal conductivity was unchanged despite Sn doping because the electrical contribution to the total thermal conductivity was very small. Consequently, Sn doping in InSe enhanced the dimensionless thermoelectric figure of merit <i>zT</i> from 0.04 to 0.14 at 800 K, mainly due to enhanced electrical properties.