Vacancy Manipulation by Ordered Mesoporous Induced Optimal Carrier Concentration and Low Lattice Thermal Conductivity in Bi<i>_x</i>Sb₂₋<i>_x</i>Te₃ Yielding Superior Thermoelectric Performance

For Bi_xSb_2- _xTe₃ (BST) in thermoelectric field, the element ratio is easily influenced by the chemical environment, deviating from the stoichiometric ratio and giving rise to various intrinsic defects. In P-type polycrystalline BST, Sb_Te and Bi_Te are the primary forms of defects. Defect engineering is a crucial strategy for optimizing the electrical transport performance of Bi₂Te₃-based materials, but achieving synchronous improvement of thermal performance is challenging. In this study, mesoporous SiO₂ is utilized to successfully mitigate the adverse impacts of vacancy defects, resulting in an enhancement of the electrical transport performance and a pronounced reduction in thermal conductivity. Crystal and the microstructure of the continuous modulation contribute to the effective phonon-electronic decoupling. Ultimately, the peak zT of Bi_0.4Sb_1.6Te₃/0.8 wt% SiO₂ (with a pore size of 4 nm) nanocomposites reaches as high as 1.5 at 348 K, and a thermoelectric conversion efficiency of 6.6% is achieved at ΔT = 222.7 K. These results present exciting possibilities for the realization of defect regulation in porous materials and hold reference significance for other material systems.