Robust (Bi,Sb) ₂ Te ₃ Thermoelectrics Due to Engineered Ion Confinement and Microstructure for Advancing Thermoelectric Power Generators

Abstract Bi 2 Te 3 ‐based alloys remain the only commercially available thermoelectrics to date. However, the extensive intrinsic defects and the “donor‐like” effect intensified by powder metallurgy significantly deteriorate the transport properties of (Bi,Sb) 2 Te 3 . Here, Cu is consistently used as the most effective dopant for performance enhancement, while substituting Te with the more electronegative S strengthens the electrostatic attraction, thereby markedly increasing the energy barrier for Cu ion migration. The optimized carrier transport, combined with microstructural evolution characterized by high‐density twins and dislocations, results in a 10% increase in room‐temperature weighted mobility and a concurrent reduction in lattice thermal conductivity by 37%. Consequently, the Bi 0.492 Cu 0.008 Sb 1.5 Te 2.95 S 0.05 sample achieves a peak ZT of 1.51 at 350 K, with ion confinement ensuring negligible performance degradation after annealing at 550 K for 20 days. The compressive strength and bending strength are also improved to 232 and 60 MPa, respectively. Furthermore, the fabricated full‐scale power generator demonstrates a maximum conversion efficiency of ≈7.0% under a Δ T of 200 K, certified by third‐party validation, and exhibits excellent operational stability, underscoring its immense potential for widespread deployment.