Phase-stabilized GeTe with optimized interfaces for high-performance thermoelectric energy conversion

The practical deployment of GeTe-based thermoelectrics has long been constrained by phase instability at elevated temperatures and severe interfacial degradation due to chemical diffusion and thermal expansion mismatches. Previous efforts to stabilize the high-performance cubic phase often result in incomplete phase suppression or compromised transport properties, while conventional electrode interface strategies exhibit poor thermomechanical reliability and inconsistent diffusion barriers. Here, we present a fully stabilized cubic GeTe system through Mn–Sb co-doping, maintaining phase stability from 300 to 750 K while simultaneously optimizing carrier concentration and electronic/thermal transport properties. This material achieves a peak zT of 1.73 at 773 K and an average zT of 1.0 across the operating range. To address interfacial instability, we introduce a cobalt diffusion barrier via magnetron sputtering, ensuring uniform coverage, good thermomechanical robustness, and a low contact resistivity of 5.2 μΩ cm2. These advancements enable the development of GeTe-based thermoelectric modules with an efficiency of 12.2% under a 480 K temperature gradient. By integrating precise phase stabilization with robust interface engineering, this study provides a viable pathway for mid-temperature waste heat recovery and reliable thermoelectric energy conversion.