Boosting the Thermoelectric Properties of Textured BiSbSe₃ via Versatile CuI Compositing

Tellurium-free BiSbSe₃ has emerged as a promising candidate for medium-temperature n-type thermoelectric (TE) materials, which is attributed to its low lattice thermal conductivity and high performance-cost ratio. However, the intrinsically poor electrical properties restrict the enhancement of TE properties. Herein, the versatile CuI is introduced into BiSbSe₃. The synergistic effects of iodine substituting for selenium and copper occupying the intercalation position collectively increase the carrier concentration. Concurrently, microstructure analysis results reveal that multiscale defects such as dislocations, (Bi,Sb)SeI nanoprecipitates, elemental segregation, and subgrain boundaries are introduced into BiSbSe₃ via CuI compositing, which enhances the multifrequency phonon scattering. Ultimately, benefiting from the trade-off between the power factor and thermal conductivity, BiSbSe₃+0.02CuI parallel to the hot-pressing direction attains an excellent ZT value of ∼ 0.64 at 673 K, representing approximately a 12-fold improvement over that of pristine BiSbSe₃. These results demonstrate a viable compositing strategy for designing high-performance BiSbSe₃ materials.