Excellent Thermoelectric Performance from In Situ Reaction between Co Nanoparticles and BiSbTe Flexible Films

Low-cost flexible thermoelectric (TE) films with excellent cooling performance are critical for the in-plane heat dissipation application based on the TE film refrigeration technology. In this work, a flexible film epoxy/Bi_0.5Sb_1.5Te₃ is developed by the incorporation of ferromagnetic Co nanoparticles to improve the electrical transport and cooling performance. The magnetic properties and microstructures clearly indicate that part of Co nanoparticles in situ reacts with Te from Bi_0.5Sb_1.5Te₃ to form CoTe₂, as well as Bi_Te' antisite defects. The electric conductivity is greatly enhanced because of the increased carrier density, while a large Seebeck coefficient is well maintained because of the extra magnetic scattering. The power factor of the flexible film with 0.2 wt % Co nanoparticles reached 2.28 mW·m^-1·K^-2 at 300 K, increased by 34% compared to the epoxy/Bi_0.5Sb_1.5Te₃ film. The maximum cooling temperature difference is 1.5 times higher compared with the epoxy/Bi_0.5Sb_1.5Te₃ film. This work provides a general method to improve the electrothermal conversion performance of BiSbTe-based flexible films through in situ reaction.