Heavy Doping by Bromine to Improve the Thermoelectric Properties of n-type Polycrystalline SnSe.

Single crystal tin selenide (SnSe) has attracted much attention for its excellent thermoelectric performance. However, polycrystalline SnSe exhibits unsatisfactory figure-of-merit due to the inferior electrical properties, especially for n-type SnSe. In this work, a high concentration of Br doping (6-12 atm%) on the Se site effectively increases the Hall carrier concentration from 1.6 × 1017 cm-3 (p-type) in undoped SnSe to 1.3 × 1019 cm-3 (n-type) in Br-doped SnSe0.88Br0.12, leading to an increased electrical conductivity close to that of a single crystal. Combined with the decreased lattice thermal conductivity due to the enhanced phonon scattering by composition fluctuation and dislocations, a peak ZT of ≈1.3 at 773 K, together with the enhanced average ZT is obtained in SnSe0.9Br0.1 along the hot pressing direction.