Br-Doped n-Type SnSe₂: Single-Crystal Growth and Thermoelectric Properties

In this work, pure, large Br-doped SnSe2 single crystals were successfully synthesized using the temperature gradient technique. Br acts as a donor, resulting in electron concentrations up to ∼6.83 × 1019 cm–3 at room temperature. All samples exhibited metal-like electrical resistivities and Seebeck coefficient behaviors over a temperature range of 300–673 K. Br doping greatly improved the power factor, especially along the in-plane direction. We observed anisotropy in the electrical conductivity, Seebeck coefficient, and, most notably, thermal conductivity. An ultralow thermal conductivity was achieved along the out-of-plane direction, leading to a maximum ZTc of 0.54 at 673 K in the Br-doped sample, which is twice as large as that of the in-plane direction, ZTa = 0.25.