Cross-Scale Defects Enable Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in Silver Nanowire-Integrated Bi2Te3/Sb2Te3 Nanoheterojunctions

Decoupling the intrinsically coupled electrical and thermal transport remains a central challenge for achieving high-performance thermoelectrics. Herein, we report a defect-modulated transport-decoupling strategy in anisotropic Bi2Te3/Sb2Te3 (BT/ST) heterojunction nanomaterials with silver nanowires. By guiding defect evolution at the BT/ST phase boundaries, nanopore-containing heterointerfaces are constructed. Combined spatially resolved EELS observations and HRTEM/IFFT suggest that nanopores are preferentially associated with dislocation-rich heterogeneous interfacial regions. These engineered nanopores and heterogeneous interfaces effectively suppress phonon transport, leading to an ultralow lattice thermal conductivity of ∼0.13 W m-1 K-1 at 600K. Meanwhile, the two-dimensional nanoplate framework provides anisotropic transport characteristics, while silver nanowires provide additional conductive pathways and modify the interfacial electronic transport, enabling enhanced electrical conductivity while preserving a high Seebeck coefficient. As a result, the electrical and thermal transport processes are spatially regulated. The optimized BT/ST nanoheterojunctions containing 2 vol % AgNWs exhibits a peak ZT⊥ of 0.74, corresponding to a substantial ∼174% enhancement compared with the pristine matrix. More importantly, the combination of suppressed phonon transport and preserved electrical transport parallel to the SPS pressing direction yields a high S∥ of 169 μV K-1 and an outstanding peak ZT∥ of 1.25 at 600 K. This work demonstrates that controllable nanopore construction and directional electrical pathway engineering are effective for realizing anisotropic carrier-phonon decoupling in high-performance thermoelectric materials.