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 × 10(17) cm(−3) (p‐type) in undoped SnSe to 1.3 × 10(19) cm(−3) (n‐type) in Br‐doped SnSe(0.88)Br(0.12), 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 SnSe(0.9)Br(0.1) along the hot pressing direction.