Defect Engineering Realizes Superior Thermoelectric Performance of GeTe

Abstract GeTe has been considered as a promising mid‐temperature thermoelectric (TE) candidate, but its zT value is severely limited by the excessive hole concentration and high thermal conductivity. Here, it is demonstrated that the TE properties of GeTe can be significantly improve by defect engineering of Sb‐Pb and AgCuTe codoping. The Sb‐Pb codoping is adopted to optimize the carrier concentration and manipulate the rhombohedral lattice distortion, leading to valence band convergence and enhanced power factor. The AgCuTe alloying introduces multiscale phonon scattering centers including dislocations and nano‐precipitates to reduce the lattice thermal conductivity in GeTe. Consequently, a maximum zT of 2.3 at 773 K and an average zT of 1.43 (300–773 K) are obtained in (Ge_0.84Sb_0.06Pb_0.1Te)_0.99(AgCuTe)_0.01. Moreover, the fabricated thermoelectric module exhibits a high output power density of 0.59 W cm^–2 and an energy conversion efficiency of 7.9% at ΔT = 500 K, suggesting hierarchical defect engineering is an effective strategy to realize high‐performance GeTe‐based thermoelectric.