Heterointerface-grain boundary defect engineering enables high-performance and mechanically robust Bi2Te3-based thermoelectric nanocomposites

The simultaneous optimization of thermoelectric (TE) performance, mechanical robustness, and device-level applicability remains a long-standing challenge for the practical deployment of Bi 2 Te 3 -based TE materials in power generation and solid-state cooling. Herein, we report a high-performance TE nanocomposite, Bi 0.3 Sb 1.7 Te 2.99 S 0.01 + 0.7 wt.% ZrO 2 , which concurrently exhibits enhanced TE properties and mechanical strength, enabling reliable device fabrication. By integrating heterogeneous interface engineering with deliberately constructed grain-boundary defect architectures—including twin boundaries, staggered lamellae, and antisite defect layers—a cooperative regulation of charge and phonon transport is achieved across multiple length scales. This defect-mediated transport modulation markedly enhances the Seebeck coefficient and power factor, while suppressing both electronic and lattice thermal conductivities, thereby effectively mitigating the intrinsic trade-off between TE efficiency and mechanical integrity. Consequently, the optimized nanocomposite delivers a peak zT max of ∼1.46 at 350 K and an average zT ave of ∼1.23 over 300–500 K, in addition to a Vickers hardness of 1.17 GPa and a compressive strength of 218 MPa. Importantly, a seven-pair TE device achieved a maximum conversion efficiency of ∼6.8% at a temperature difference of 200 K and a maximum cooling temperature difference of ∼63.4 K at 300 K. This study demonstrates that heterointerface–grain boundary defect engineering provides an effective and scalable strategy to simultaneously advance TE performance, mechanical reliability, and device-level functionality in Bi 2 Te 3 -based TE nanocomposites.