Coupled Vacancy and Phonon-Scattering Engineering Drive Defect Evolution Toward Multifunctional High-Performance...

Thermoelectric (TE) materials with high-efficiency solid-state cooling and low-grade heat harvesting are crucial for sustainable energy technologies. Although Bi₂Te₃-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_0.4Sb_1.6Te_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_0.4Sb_1.6Te_2.97Se_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 Bi₂Te₃-based thermoelectrics.