Boosting thermoelectric performance of hydrothermal SnSe2 via Br doping-induced high carrier concentration and low thermal conductivity

Anion-site doping represents a potent approach to tailor the electronic structure and transport properties of SnSe2. Herein, Br-doped SnSe2 bulk materials were successfully fabricated through a hydrothermal–annealing–sintering route, and the thermoelectric transport mechanisms were systematically investigated. Due to the valence electron discrepancy between Br and Se, the incorporation of Br into the matrix acts as a high-efficiency donor, triggering a degenerate semiconductor behavior. Consequently, the carrier concentration reached 2.38 × 1020 cm−3. Crucially, Br doping facilitates the microstructural texturing alignment during the consolidation process, thereby mitigating grain boundary potentials. This synergistic effect significantly boosts electrical conductivity, yielding a room-temperature power factor of 5.2 μW cm−1 K−2. Furthermore, the intensified point defect phonon scattering induced by Br substitution outweighs the weakened boundary scattering from grain growth, thereby suppressing the κ. As a result, a maximum ZT value of 0.47 is achieved in SnSe1.87Br0.13 at 773 K, which stands as a highly competitive performance among hydrothermally processed SnSe2. This work provides deep insights into the transport optimization of layered chalcogenides for green energy applications.