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

Bi₂Te₃-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-xSb_xTe₃ 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 <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:semantics><mml:msubsup><mml:mi>Sb</mml:mi> <mml:mi>Te</mml:mi> <mml:msup><mml:mrow></mml:mrow> <mml:mo>'</mml:mo></mml:msup> </mml:msubsup> <mml:annotation>${\mathrm{Sb}}_{{\mathrm{Te}}}^{\mathrm{^{\prime}}}$</mml:annotation></mml:semantics> </mml:math> 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 Bi₂Te₃-based power generators in low-grade waste heat recovery.