Cu/Sb Codoping for Tuning Carrier Concentration and Thermoelectric Performance of GeTe-Based Alloys with Ultralow Lattice Thermal Conductivity

Pristine GeTe shows promising thermoelectric performance but is limited by the high carrier concentration (n H) from Ge vacancies and thermal conductivity. Herein, Cu/Sb was chosen as codopants to suppress the high n H and to decrease thermal conductivity. In this condition, a promising zT of ∼1.62 under 773 K was acquired in the Ge0.85Te­(CuSb)0.075 system proposed in this paper/work. Results show that as the dopant concentration increases, the power factor rises due to the reduction of the n H to ∼1 × 1020 cm–3. Apart from this, the total thermal conductivity also declines from ∼7.4 W m–1 K–1 to ∼1.59 W m–1 K–1 originating from an ultralow lattice thermal conductivity, in which the multiscatter mechanism from grain boundaries and point defect disperses the frequency phonons differently. The findings in this paper combine thermal and electronic strategies and lay the foundation to develop Pb-free thermoelectric materials.