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.