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

Abstract

Superior electronic performance due to the highly degenerated Σ valence band (Nv∼12) makes rhombohedral GeTe a promising low‐temperature (<600 K) thermoelectric candidate. Minimizing lattice thermal conductivity (κL) is an essential route for enhancing thermoelectric performance, but the temperature‐dependent κL, corelated to T−1, makes its reduction difficult at low temperature. In this work, a room‐temperature κL of ≈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 zTavg. of ≈1.2 within 300–625 K are achieved, leading to a conversion efficiency of ≈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.