Manipulating Atomic Disorder and Mesoscale Architectures for High-Efficiency Thermoelectric Modules

Decoupling electron and phonon transport remains the central challenge in designing high-performance thermoelectric materials for low-grade heat recovery. Conventional optimization strategies for Bi₂Te₃-based alloys typically isolate defect engineering from microstructure modulation, often leading to performance trade-offs. Here, we demonstrate a strategy that simultaneously manipulates atomic disorder and mesoscale architectures via an in situ solid-state reaction in p-type Bi_0.5Sb_1.5Te₃. By incorporating PbTiO₃ precursors, we trigger a thermodynamically driven reaction: at the atomic scale, Pb atoms substitutionally occupy Sb sites to induce chemical disorder and optimize the Fermi level; at the mesoscale, residual Ti species segregate to form PbTiO₃@TiO₂ core-shell precipitates. This hierarchical structural engineering acts as a frequency-selective barrier, drastically reducing lattice thermal conductivity without compromising carrier mobility. Consequently, the 0.5 mol% composite achieves a peak figure of merit of 1.47 at 333 K. Translating this material-level breakthrough into a device, we fabricated a thermoelectric module that delivers a conversion efficiency of ∼7% and an output power of 13.1 mW under a temperature difference of 180 K. This work establishes a generalizable protocol for functionalizing thermoelectric systems via coupled defect chemistry and interface engineering, bridging the gap between fundamental transport physics and practical energy harvesting.