Simultaneous Suppression of Phonon Transport and Carrier Concentration for Efficient Rhombohedral GeTe Thermoelectric

Superior electronic performance due to the highly degenerated Sigma valence band (N-v similar to 12) makes rhombohedral GeTe a promising low-temperature (<600 K) thermoelectric candidate. Minimizing lattice thermal conductivity (kappa(L)) is an essential route for enhancing thermoelectric performance, but the temperature-dependent kappa(L), corelated to T-1, makes its reduction difficult at low temperature. In this work, a room-temperature kappa(L) of approximate to 0.55 W m(-1)-K-1, the lowest ever reported in GeTe-based thermoelectric, is realized in (Ge1-ySbyTe)(1-x)(Cu8GeSe6)(x), primarily due to strong phonon scattering induced by point defects and precipitates. Simultaneously, Cu8GeSe6-alloying effectively suppresses the precipitation of Ge, enabling the optimization of carrier concentration with the additional help of aliovalent Sb doping. As a result, an extraordinary peak zT of up to 2.3 and an average zT(avg.) of approximate to 1.2 within 300-625 K are achieved, leading to a conversion efficiency of approximate to 9% at a temperature difference of 282 K. This work robustly demonstrates its potential as a promising component in thermoelectric generator utilizing low-grade waste heat.