Thermoelectric Cooling Performance Enhancement in BiSeTe Alloy by Microstructure Modulation via Hot Extrusion

The demand for high-performance materials in thermoelectric (TE) technology has driven continuous efforts to enhance the performance of commercialized Bi₂Te₃-based thermoelectric materials. Here, we report success in achieving significant performance improvements in n-type Bi₂Te_2.8Se_0.2S_0.01 through the implementation of a hot extrusion manufacturing process. This tailored manufacturing process has yielded a desired microstructure characterized by grain growth and preferred orientations. The resulting enlarged grain-based microstructure exhibits reduced dislocations and defects that originated from plastic deformation during extrusion and post annealing. As such, the charge carrier mobility is significantly enhanced, leading to an ultrahigh power factor of approximately 51 μW cm⁻¹ K⁻² at ambient temperature. Consequently, a maximum figure of merit (zT) of 1.12 is achieved at 348 K in the combination of extrusion and annealing procedures. Using the synthesized n-type Bi₂Te_2.8Se_0.2S_0.01 material, full-scale cooling modules have been fabricated. These modules demonstrate record cooling performance, with a maximum temperature difference (ΔT) of 73.9 K at a hot-side temperature of 300 K and a maximum cooling power density of 2.2 W cm⁻². The cooling performance of these TE devices surpasses that of commercially available devices, establishing their potential for next-generation TE cooling applications.