Doping Copper Selenide for Tuning the Crystal Structure and Thermoelectric Performance of Germanium Telluride-Based Materials

Germanium telluride (GeTe) compounds exhibit excellent thermoelectric performance. In this study, copper selenide (Cu₂Se) was used to tune the crystal structure and carrier concentration (n_H) of GeTe materials. The zT of the 1% Cu₂Se-doped GeTe sample reaches 1.32, which is 52% higher than that of the pure phase. The results show that Cu₂Se tunes the GeTe crystal structure and carrier concentration to achieve promising enhancements to the thermoelectric performance. Meanwhile, a herringbone-like crystal structure that reduces the lattice thermal conductivity was observed. However, because the directional movement of Cu ions at high temperatures leads to an increase in electrical conductivity, the electronic thermal conductivity also increased. This study focuses on crystal engineering strategies for the study of nontoxic thermoelectric materials.