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.