Preparation of carbon nanotube/inorganic nanoparticle composite films: CNTs with exfoliated Bi2Si2Te6 nanosheets for carbon-based thermoelectric generator applications

Abstract

Our flexible thermoelectric (TE) composite film is composed of Bi₂Si₂Te₆ nanosheets (BST NSs) and carbon nanotubes (CNTs). It is synthesized with a simple solution-processable method. BST NSs are Li-intercalated and chemically exfoliated from a bulk BST ingot. The as-prepared CNTs are distributed into the BST NSs, leading to the formation of the BST NS/CNT composite film. The prepared BST NS/CNT composite film shows an outstanding power factor due to enhanced electrical conductivity because of the CNT addition. When the carrier transport properties of the BST NS/CNT composite film were investigated to explain the improved TE properties, we found that carrier concentration and mobility were increased by incorporating CNTs into the BST NS matrix. The maximum power factor (PF) of the BST NS/CNT composite film is ∼498.3 μW m⁻¹ K⁻² at 423 K, which is significantly higher than that of pure BST NSs. Bending tests confirm the outstanding mechanical durability and flexibility of the composite film and the PF only decreases by ∼4% after 1000 bending cycles. A simple flexible TE generator composed of 8 strips of the BST NS/CNT composite film was constructed; this generator displayed an output power and power density of ∼2.96 μW and ∼3.1 W m⁻², respectively, at a relatively small temperature difference of 40 K. The synthesized TE composite film demonstrates the potential of carbon-based TE materials as wearable and flexible substrates for energy harvesting devices.