Screening Weldable Metal Electrodes for Ag₂Se Thermoelectric Devices below 300 °C

Thermoelectricity has been considered as the most important solution of generating electricity, particularly from low-grade heat below 300 °C. Despite efforts in recent years on exploring alternative materials to only commercialized Bi₂Te₃, the practical implementation of these new materials has been hindered by inadequate investigation into device design. Given that the utilization of weldable electrodes offers advantages in technical compatibility for a large-scale assembly of thermoelectric elements into modules, a thorough investigation into the potential of weldable metal electrodes at T < 300 °C is imperative. In this work, the diffusion of 11 kinds of thermoelectric materials in common weldable metals (Ni, Fe, Cu, and Ag) was screened. Ag is sorted out as a promising weldable electrode that can directly bond to thermoelectric Ag₂Se in this temperature range, leading to a minimization of an interfacial contact resistivity down to 11 μΩ cm² in a design of the Ag/Ag₂Se/Ag structure. The conversion efficiency of ∼3% at ΔT of 95 K with an excellent stability indicates Ag₂Se as a top alternative to n-type Bi₂Te₃ for low-grade heat recovery.