Ultralow Lattice Thermal Conductivity and Extraordinary Thermoelectric Performance in Environmentally Friendly SnTe Achieved Through Band Convergence and Strong Point Defect Scattering

ABSTRACT Here, we achieve a high peak ZT of 1.6 along with an outstanding average ZT of ∼1 through synergistic band convergence and strong point defect scattering in SnTe. Ge‐Mn‐Sb codoping introduces abundant point defects that effectively scatter high‐frequency phonons, which leads to an ultralow lattice thermal conductivity of 0.26 W m − 1 K − 1 at 873 K. Notably, alloying with Ge‐Mn‐Sb effectively reduces the energy offset between the light and heavy valence bands in SnTe, leading to pronounced band convergence. This refined band structure significantly enhances the Seebeck coefficient. The improved Seebeck coefficient coupling with optimized carrier concentration, gives rise to a markedly enhanced power factor over a broad temperature range. Our finding provides a perspective for the rational design of high‐performance thermoelectric materials with balanced electrical and thermal transport properties.