Maximizing the performance of n-type Mg₃Bi₂ based materials for room-temperature power generation and thermoelectric cooling

Although the thermoelectric effect was discovered around 200 years ago, the main application in practice is thermoelectric cooling using the traditional Bi₂Te₃. The related studies of new and efficient room-temperature thermoelectric materials and modules have, however, not come to fruition yet. In this work, the electronic properties of n-type Mg_3.2Bi_1.5Sb_0.5 material are maximized via delicate microstructural design with the aim of eliminating the thermal grain boundary resistance, eventually leading to a high zT above 1 over a broad temperature range from 323 K to 423 K. Importantly, we further demonstrated a great breakthrough in the non-Bi₂Te₃ thermoelectric module, coupled with the high-performance p-type α-MgAgSb, for room-temperature power generation and thermoelectric cooling. A high conversion efficiency of ~2.8% at the temperature difference of 95 K and a maximum temperature difference of 56.5 K are experimentally achieved. If the interfacial contact resistance is further reduced, our non-Bi₂Te₃ module may rival the long-standing champion commercial Bi₂Te₃ system. Overall, this work represents a substantial step towards the real thermoelectric application using non-Bi₂Te₃ materials and devices.