Effective Diffusion Barrier Layer Achieves Thermal Stability for n-Type Bi₂Te_2.7Se_0.3 Thermoelectric Generators

Bismuth telluride alloys are widely used in the commercial thermoelectric market due to their outstanding thermoelectric performance near room temperature. To improve the performance and stability of n-type Bi₂Te₃ devices aiming at power generation applications, this work focuses on the exploration of potential metal barrier materials between the thermoelectric material and the electrode, via the revelation of the diffusion behaviors for 11 metals in n-type Bi₂Te_2.7Se_0.3. Ti was identified as a potential one due to its excellent bonding with Bi₂Te_2.7Se_0.3 sintered at a relatively low temperature and low diffusion coefficient. As a demonstration, an n-type Bi₂Te_2.7Se_0.3 single-leg device and module for power generation were fabricated using Ti as the barrier layer between the thermoelectric materials and weldable Ni electrodes. The nearly unchanged output power and conversion efficiency after several thermal cycles and long-term stability measurements at a hot-side temperature of 495 K for 160 h robustly demonstrate the excellent thermal stability for these generators using Ti as a barrier layer.