High Thermoelectric Performance and Energy Conversion in Hg‐doped GeTe

Abstract Due to the high intrinsic zT of≈1.0 by multi‐band valleys, GeTe‐based thermoelectric materials are promising for medium‐temperature applications. In this work, the extraordinary role of the new dopant Hg on the electro‐phonon transport of GeTe is comprehensively elucidated. According to the first‐principles calculations, Hg doping can effectively reduce the energy offset between light and heavy valence bands, and increase the density‐of‐states effective mass from 1.45 m₀ to 2.58 m₀. Experimentally, the (GeTe)_1‐x(HgTe)_x samples are demonstrated to possess an enhanced room‐temperature Seebeck coefficient from 30.3 to 59.9 µV K⁻¹, plus an outstanding average power factor (300–773 K) of 28.8 µW cm⁻¹ K⁻². The Pb‐Bi codoping further optimizes the hole concentration and significantly suppresses the lattice thermal conductivity to 0.47 W m⁻¹ K⁻¹ by the induced various phonon scattering centers including dense point defects, grain boundaries, dislocations, and nano‐precipitates. Consequently, a high zT_max of 2.31 at 650 K and an average zT_avg of 1.52 between 300 and 773 K are obtained in (Ge_0.89Pb_0.08Bi_0.03Te)_0.97(HgTe)_0.03. Utilizing the optimized materials, achieving a high energy conversion efficiency of 10.8% at a temperature difference of 500 K in the fabricated 7‐pair thermoelectric module. This study clarifies the multiple benefits of Hg doping in GeTe‐based derivatives and provides a framework for designing high‐performance medium‐temperature thermoelectric materials.