Thermoelectric properties of GeSe

AbstractThe recently reported superior thermoelectric performance of SnSe, motivates the current work on the thermoelectric properties of polycrystalline GeSe, an analog compound with the same crystal structure. Due to the extremely low carrier concentration in intrinsic GeSe, various dopants are utilized to substitute either Ge or Se for increasing the carrier concentration and therefore for optimizing the thermoelectric power factor. It is shown that Ag-substitution on Ge site is the most effective, which enables a hole concentration up to ∼1018 cm−3. A further isovalent substitution by Pb and Sn leads to an effective reduction in the lattice thermal conductivity. A peak figure of merit, zT of ∼0.2 at 700 K can be achieved in Ag0.01Ge0.79Sn0.2Se, a composition with the highest carrier concentration. The transport properties can be well described by a single parabolic band model with a dominant carrier scattering by acoustic phonons at high temperatures (>500 K). This further enables a prediction on the maximal zT of ∼0.6 at 700 K and the corresponding carrier concentration of ∼5 × 1019 cm−3