Development of silicide thermoelectric modules based on high purity Si and recycled Si-kerf: A contact resistance investigation

This work describes the development of thermoelectric modules based on n-type magnesium silicide (Bi-doped Mg2SixSn1-x) and p-type manganese silicide (Al-doped MnSi1.73) synthesized from high purity Si (commercially available) and recycled Si-kerf from the PV industry. Metallization based on sputtered Ni/Cu bilayers and bonding through the pressure assisted silver sintering technique is examined. Specific contact resistance analysis is conducted to evaluate the aptness of the metallization and bonding methodologies, through the transfer length- and the scanning probe-methods respectively. Deposition conditions are optimized, and reduction of the metallization-related contact resistance is achieved. Improvement of silver sintering bonding is enabled through the increase of the thermoelectric legs surface roughness, which is accompanied by lower cumulative specific contact resistance values. Fabrication of 4-leg thermoelectric modules, serving as proof-of-concept prototypes for the recycling of Si-kerf, is showcased. High power densities of similar to 0.7 W/cm(2) and similar to 0.53 W/cm(2) at Delta T approximate to 380 degrees C for the high purity Si- and the Si-kerf- based proof-of-concept devices respectively are measured. Good agreement between experimental and simulated (COMSOL Multiphysics (R)) performance is shown. Upscaling from 4-leg proof-of-concept prototypes to larger 16-leg Si-kerf based modules is also achieved, with high power densities also being demonstrated.