High Conversion Efficiency in Intrinsic High Power‐Density Mg ₂ Sn‐GeTe Thermoelectric Generator

Thermoelectric generators (TEGs) offer a sustainable solution for thermal energy harvesting, where maximizing energy output necessitates achieving both high power density and high conversion efficiency. However, TEGs with intrinsically high power density by employing high power factor materials often face efficiency limitations due to their usually high thermal conductivity. Here, intrinsically high power density TEGs based on Mg₂Sn-GeTe for the first time is presented, simultaneously delivering a remarkable conversion efficiency of 9% under a temperature gradient of 418 K, thereby setting a new benchmark in the field. This exceptional performance is attributed to the significant balance between the moderating carrier and phonon transport in Mg₂Sn, enabled by a stepwise aliovalent Sb and Bi solid solution, without over-compromising its outstanding power factor. Consequently, a high thermoelectric figure of merit of 1.4 is achieved in Mg₂Sn_0.8(Sb_0.5Bi_0.5)_0.2. The high-performance Mg₂Sn-GeTe TEGs introduced here represent a significant advancement in thermoelectric technology, offering an innovative and efficient solution for off-grid energy supply in waste-heat-rich environments.