Recent Trends of Ternary, Quaternary Half-Heusler Thermoelectric Materials and Contact Resistance Effect on Their Power Output Efficiency

Climate change is one of the most pressing global issues, owing to the high carbon footprint generated during conventional power generation via coal consumption and gasoline-fuelled exhaust. Furthermore, nearly half of the total energy is lost as heat. Suitable thermoelectric (TE) devices can convert waste heat into green/clean energy. Moreover, these devices have no moving parts, require no maintenance, and are environmentally friendly. A better TE device's thermoelectric performance (zT) should be highly cost-effective for process scaling. Because of their low cost, narrow band gap, better contact engineering, decent electrical properties, and high mechanical performance, Half-Heusler (HH) compounds (space group Fm-3 m) have been considered the best candidate materials worldwide. However, these materials have a high thermal conductivity. The high thermoelectric performance of HH compounds was achieved through iso-electronic doping and nanostructuring, which reduced thermal conductivity significantly. The current report briefly overviews 17, 18, 19, and 21 valence electron count (VEC) HH materials and their effects on thermal conductivity and zT. Finally, using cumulative temperature dependence (CTD) and constant property models (CPM), the theoretical estimation of power density and efficiency was calculated by considering the materials' thermoelectric performance and contact resistance.