A robust thermoelectric module based on MgAgSb/Mg(Sb,Bi) with a conversion efficiency of 8.5% and a maximum cooling of 72 K

The applications of thermoelectric (TE) technology around room temperature are monopolized by bismuth telluride (Bi 2 Te 3 ). However, due to the toxicity and scarcity of tellurium (Te), it is vital to develop a next-generation technology to mitigate the potential bottleneck in raw material supply for a sustainable future. Hereby, we develop a Te-free n-type compound Mg 3 Sb 0.6 Bi 1.4 for near-room-temperature applications. A higher sintering temperature of up to 1073 K is found to be beneficial for reducing the electrical resistivity, but only if Mg is heavily overcompensated in the initial stoichiometry. The optimizations of processing and doping yield a high average zT of 1.1 in between 300 K and 573 K. Together with the p-type MgAgSb, we demonstrate module-level conversion efficiencies of 3% and 8.5% under temperature differences of 75 K and 260 K, respectively, and concomitantly a maximum cooling of 72 K when the module is used as a cooler. Besides, the module displays exceptional thermal robustness with a < 10% loss of the output power after thermal cycling for ∼32 000 times between 323 K and 500 K. These proof-of-principle demonstrations will pave the way for robust, high-performance, and sustainable solid-state power generation and cooling to substitute highly scarce and toxic Bi 2 Te 3 . Demonstration of a robust, tellurium-free thermoelectric module for near-room-temperature applications with a high conversion efficiency of 8.5% and a maximum cooling of 72 K.