Realizing High Thermoelectric Performance in GeTe‐Based Alloys Without Lead Addition

Abstract GeTe‐based materials exhibit excellent thermoelectric performance, making them highly promising for mid‐temperature heat harvests. However, most high‐performance GeTe‐related studies desperately relied on lead element doping, which conflicts with the original intention of developing green and sustainable energy. This study reports that an ultrahigh peak figure of merit ZT max ≈2.7 at 800 K and an average figure of merit ZT avg ≈1.6 from 300 to 800 K can be realized without any lead addition. This study first incorporates Mg into the GeTe matrix to induce band convergence, then alloys Sb 2 Te 3 /Bi 2 Te 3 simultaneously into the lattice to construct ordered Ge vacancy structures. The appearance of ordered Ge vacancies not only significantly strengthened phonon scattering but also further modulated the valence band degeneracy near the Fermi level for a high power factor. Additionally, a 2 × 2 π‐type segmented thermoelectric module is based mainly on the lead‐free GeTe materials is also fabricated in this work, and achieved a high maximal conversion efficiency η max ≈10.5% as well as a power density of 1.22 W·cm− 2 at a temperature difference of 474 K. This research provides a feasible solution for balancing electrical/thermal transports and achieving high‐efficiency thermoelectric power generation devices.