Thermo-Electric-Mechanical Coupling Selects Barrier Layer for Advanced Bismuth Telluride Thermoelectric Generator

The long-term stability of thermoelectric generators, including those based on Bi₂Te₃, is hindered by the lack of ideal thermoelectric barrier materials (TEbMs). Conventional selection methods for TEbMs mainly rely on trial-and-error, which is time-consuming and does not reveal the underlying mechanisms. In this study, a new design principle for selecting TEbMs based on thermo–electric–mechanical coupling is proposed. By combining the phase diagram predictions with the thermal expansion coefficients and electrical resistivities of the potential reactants, the Ni₂SbTe₂ and NiTe₂ compounds are identified as ideal TEbMs for (Bi,Sb)₂Te₃ and Bi₂(Te,Se)₃, respectively, leading to interfaces with high thermal stability, low contact resistivity, and high strength. The fabricated thermoelectric generator achieves a competitive conversion efficiency of 7.1% and a power density of 0.49 W cm⁻² at hot-side and cold-side temperatures of 523 and 296 K, respectively. Moreover, performance degradation is negligible after 200 h of cycling. This work demonstrates progress toward stable high-performance service, provides the foundation for applications in low-grade heat recovery, and offers new insights for more thermoelectric generators.