High-Power-Density Skutterudite-Based Thermoelectric Modules with Ultralow Contact Resistivity Using Fe–Ni Metallization Layers

Most reported thermoelectric modules suffer from considerable power loss due to high electrical and thermal resistivity arising at the interface between thermoelectric legs and metallic contacts. Despite increasing complaints on this critical problem, it has been scarcely tackled. Here we report the metallization layer of Fe–Ni alloy seamlessly securing skutterudite materials and metallic electrodes, allowing for a minimal loss of energy transferred from the former. It is applied to an 8-couple thermoelectric module that consists of n-type (Mm,Sm)yCo4Sb12 (ZTmax = 0.9) and p-type DDyFe3CoSb12 (ZTmax = 0.7) skutterudite materials. It performs as a diffusion barrier suppressing chemical reactions to produce a secondary phase at the interface. Consequent high thermal stability of the module results in the lowest reported electrical contact resistivity of 2.2–2.5 μΩ cm2 and one of the highest thermoelectric power density of 2.1 W cm–2 for a temperature difference of 570 K. Employing a scanning transmission electron microscope equipped with an energy-dispersive X-ray spectroscope detector, we confirmed that it is negligible for atomic diffusion across the interface and resulting formation of a detrimental secondary phase to energy transfer and thermal stability of the thermoelectric module.