Fabrication and excellent performances of Bi0.5Sb1.5Te3/epoxy flexible thermoelectric cooling devices

Highlights: • High-performance Bi_0.5Sb_1.5Te₃/epoxy films are fabricated by hot-pressing curing. • (000l) orientation, defects reduction and densification are simultaneously realized. • All the electrical properties parameters (μ, σ, α) are simultaneously increased. • High-performance TE cooling devices are fabricated with the (000 l)-oriented films. How to fabricate flexible thermoelectric (TE) films with excellent electrical transport properties remains a major bottleneck for high-performance flexible TE cooling devices. Herein, a simple and efficient method is developed to fabricate high-performance flexible TE cooling device by selecting Bi_0.5Sb_1.5Te₃ as TE component and epoxy resin as adhesive. It is discovered that the (000l) preferential orientation of Bi_0.5Sb_1.5Te₃ grains could be successfully realized in Bi_0.5Sb_1.5Te₃/epoxy thick films by hot-pressing curing process, thus causing the remarkable enhancement in the electrical transport properties. The highest power factor of the (000l)-oriented Bi_0.5Sb_1.5Te₃/epoxy thick films reached 0.84 mW m⁻¹ K⁻² at 300 K, increased by 250% and 223% as compared with that of our non-pressure thick film and the highest value by other groups, respectively. A prototype flexible TE cooling device had been fabricated with the Bi_0.5Sb_1.5Te₃/epoxy thick films. The stable temperature difference of the prototype device reached 6.2 K under a working current of 0.06 A, increased by about 24% as compared with the highest temperature difference of 5 K reported by other groups. Our work demonstrates that the hot-pressing curing process provides an effective approach to fabricate high-performance flexible TE cooling devices with Bi_0.5Sb_1.5Te₃/epoxy thick films through the (000l) preferential orientation.