Rashba Effect Maximizes Thermoelectric Performance of GeTe Derivatives

Advances in thermoelectrics are motivated by the innovation of thermoelectric theories. The Rashba effect, spin-dependent band splitting, paves a new path to enhance thermoelectric performance. Herein, we investigate the Rashba effect in GeTe, in which the rhombohedral distortion provides a unique handle to examine the mechanism of the Rashba effect for tuning thermoelectric properties. Fundamentally, we discover that the Rashba effect originates from the specific atomic site displacement. Experimentally, Sn-doped GeTe has a strong Rashba effect and yields an ultra-high power factor, meanwhile additional Sb alloying effectively tunes the carrier concentration. Moreover, microstructure characterizations reveal that the co-existence of grain boundaries, nanoprecipitates, and stacking faults significantly reinforces phonon scatterings and leads to an ultra-low lattice thermal conductivity. Finally, a high figure of merit is achieved in Ge1-x-ySnxSbyTe. The demonstrated benchmark figure of merit originated from the Rashba effect can provide a promising arena for enhancing thermoelectric performance in wide materials.