Coupled Vacancy and Phonon‐Scattering Engineering Drive Defect Evolution Toward Multifunctional High‐Performance Bi ₂ Te ₃ Thermoelectrics

ABSTRACT Thermoelectric (TE) materials with high‐efficiency solid‐state cooling and low‐grade heat harvesting are crucial for sustainable energy technologies. Although Bi ₂ Te ₃ ‐based compounds remain the only commercially viable near‐room‐temperature TE system, their deployment is still constrained by moderate conversion efficiency, limited mechanical robustness, and restricted multifunctionality. Here, we propose a dual‐regulation strategy that integrates intermetallic ZnSb and Se dopants to synergistically modulate carrier and phonon transport in Bi _0.4 Sb _1.6 Te _3.01 . ZnSb incorporation compensates for Sb vacancies, suppresses Te volatilization, and decreases carrier concentration, thereby enhancing the Seebeck coefficient and power factor. Concurrently, Se doping introduces hierarchical phonon‐scattering centers and induces swapped‐bilayer configurations near twin boundaries, strengthening interlayer coupling and improving mechanical integrity. The optimized Bi _0.4 Sb _1.6 Te _2.97 Se _0.04 + 0.15% ZnSb achieves a peak zT of ∼1.51 at 353 K and an average zT of ∼1.47 below 403 K, together with high Vickers hardness (∼97 Hv) and compressive strength (∼188 MPa). A finite‐element‐optimized multifunctional device further delivers a maximum cooling temperature difference of ∼70 K at 303 K and a power‐generation efficiency of ∼7.1% under a 208 K temperature gradient, with exceptional stability under room‐temperature wearable conditions. This study establishes a scalable design framework linking atomic‐scale defect manipulation to device‐level performance for practical, multifunctional Bi ₂ Te ₃ ‐based thermoelectrics.