Compromising Configurational Entropy Leading to Exceptional Thermoelectric Properties in SnTe‐Based Materials

Incorporating multiple atoms with different masses and radii at distinct atomic sites within a lattice matrix can increase its entropy and, in turn, enable a synergistic approach to both band structure and microstructure engineering. Modifying the band structure enhances electrical transport properties, while changes in the microstructure effectively suppress thermal transport properties, leading to significantly improved thermoelectric performance. Here, entropy engineering is employed to enhance the thermoelectric performance of the SnTe material system. The synergistic alloying of Ge, Mn, and In significantly alters the electronic band structure by merging four valence bands namely L, Σ, Λ, and X, and creating a resonant energy state near the Fermi level, resulting in an outstanding Seebeck coefficient of ≈97 µV K −1 at room temperature. The high density of point defects, Ge secondary phases, amorphous interfaces, phono–phonon interactions, and grain boundaries significantly disrupts the movement of heat‐carrying phonons, leading to an exceptionally low lattice thermal conductivity of 0.32 W m −1 K −1 , pushing it below the amorphous limit. Consequently, a peak figure of merit of 1.64 achieves at 873 K in Sn 0.71 Ge 0.2 Mn 0.07 In 0.02 Te. These findings lay the groundwork for developing advanced thermoelectric materials via entropy engineering.