Lattice Regularization by Manipulating Over‐Stoichiometric Defects Yields High‐Performance (Bi,Sb) ₂ Te ₃ Thermoelectrics

Abstract Bi ₂ Te ₃ ‐based alloys have historically dominated the commercial sector of near‐ambient‐temperature thermoelectric technology. However, the massive intrinsic defects form the “donor‐like” effect and affect the transport properties of Bi _{2− x} Sb _x Te ₃ significantly. Here, it is demonstrated that the over‐stoichiometric Sb fills Te vacancies and weakens the defect scattering, resulting in a desirable carrier mobility. The boost‐generated antisite defects also compensate for the extra hole carries. Combined with dilute Cu doping, the global microstructural modulation is synergistically promoted, characterized by Sb coherent nanoprecipitates and high‐density twins. Benefitting from the decoupled electrical‐thermal transport, the peak ZT is improved to ≈1.50 at 350 K, with an average ZT of 1.25 from 300 to 500 K. The further designed and integrated 17‐pair power generators exhibit ultrahigh conversion efficiency, reaching 6.7% under a 200 K temperature gradient, and show excellent operational stability. These achievements hold great potential for advancing Bi ₂ Te ₃ ‐based power generators in low‐grade waste heat recovery.