Large effective mass and ultralow thermal conductivity lead to high thermoelectric performance in the high-entropy semiconductor MnGeAgBiTe₄

Entropy engineering has emerged as an effective strategy to optimize the lattice and electronic structures of thermoelectric (TE) materials, with significant efforts toward achieving exceptional TE performance. In this study, we carried out entropy engineering on the well-known binary compound MnTe by both the partial Ge substitution of Mn and the mixture of AgBiTe (2) in the form of a solid solution. Such an engineering strategy results in the formation of the high-entropy quintuple semiconductor MnGeAgBiTe (4) , stabilizes the single-phase rock-salt structure without the occurrence of impurity, and remarkably improves the TE properties. High-entropy engineering simultaneously enhances the carrier concentration and mobility in MnGeAgBiTe (4) compared with pristine MnTe. Furthermore, the first-principles calculations reveal the multi-peak nature of MnGeAgBiTe (4) , in consistence with a high effective band mass of 5.1 m (e) estimated from the Pisarenko line. Consequently, an excellent power factor of 10.5 mu W cm (-1) K (-2) and an ultralow lattice thermal conductivity kappa (l) similar to 0.34 W m (-1) K (-1) at temperature T = 773 K are obtained in MnGeAgBiTe (4.) These superior electrical and thermal transport properties lead to a maximal ZT of similar to 1.09 at T = 773 K and an average ZT of similar to 0.90 from 400 K to 773 K.