Hierarchical Architectural Structures Induce High Performance in n‐Type GeTe‐Based Thermoelectrics

Abstract

Compatible p‐ and n‐type materials are necessary for high‐performance GeTe thermoelectric modules, where the n‐type counterparts are in urgent need. Here, it is reported that the p‐type GeTe can be tuned into n‐type by decreasing the formation energy of Te vacancies via AgBiTe ₂ alloying. AgBiTe ₂ alloying induces Ag ₂Te precipitates and tunes the carrier concentration close to the optimal level, leading to a high‐power factor of 6.2 µW cm ⁻¹ K ⁻² at 423 K. Particularly, the observed hierarchical architectural structures, including phase boundaries, nano‐precipitates, and point defects, contribute an ultralow lattice thermal conductivity of 0.39 W m ⁻¹ K ⁻¹ at 423 K. Correspondingly, an increased ZT of 0.5 at 423 K is observed in n‐type (GeTe) _0.45(AgBiTe ₂) _0.55. Furthermore, a single‐leg module demonstrates a maximum η of 6.6% at the temperature range from 300 to 500 K. This study indicates that AgBiTe ₂ alloying can successfully turn GeTe into n‐type with simultaneously optimized thermoelectric performance.