Synergistic optimization of the thermoelectric performance of BiSbSe3 using doping and multi-scale defect engineering

Abstract

Thermoelectric materials are anticipated to emerge as novel sustainable energy sources in the near future. Te-free BiSbSe₃ with an orthogonal crystal structure is considered as a promising candidate for medium-temperature thermoelectric materials due to its ultra-low thermal conductivity. However, the poor electrical transport performance limits its advance. In this work, BiSbSe_3−x−yBr_xI_y (x = 0, 0.12, 0.18; y = 0, 0.04, 0.06) samples were prepared through a combination of melting and hot-pressing sintering, and their thermoelectric properties were optimized by doping and multi-scale defect engineering. Specifically, the codoping of Br and I elements can effectively provide additional electrons and significantly enhance electrical conductivity. Based on defect engineering, an “all-scale hierarchical defects - full-frequency phonon scattering” mechanism was proposed to minimize the lattice thermal conductivity. As a result, an ultralow lattice thermal conductivity of ∼0.19 W m⁻¹ K⁻¹ and a peak ZT of ∼0.66 at 673 K are achieved for BiSbSe_2.76Br_0.18I_0.06. This work reveals the critical synergistic effect of codoping and multi-scale defect engineering on enhancing the thermoelectric properties of Te-free BiSbSe₃ materials.