Enhanced Thermoelectric Properties of Exfoliated BN Nanosheets/Single-Walled Carbon Nanotube Composite Films for Applications in Flexible Electronics

Single-walled carbon nanotube (SWCNT)-based flexible thermoelectric films exhibit potential application in wearable electronics due to their good electrical conductivity (σ) and high flexibility. Nevertheless, the low Seebeck coefficient (S) greatly limits their thermoelectric application. The high S of inorganic boron nitride nanosheets is expected to make up for the low S of SWCNT. In this work, exfoliated boron nitride nanosheets (EBNS) are first prepared by solvothermal exfoliation of hexagonal boron nitride (h-BN), which are composited with SWCNT through a simple mixing and filtration method to prepare self-supporting EBNS/SWCNT films with improved thermoelectric properties. Here, the energy filtering effect at the EBNS/SWCNT interface significantly improves the S values of the films. The results show that the maximum S of the EBNS/SWCNT at room temperature is 50.6 μV K^–1 and the maximum power factor (PF) is 116.1 μW m^–1 K^–2 at the EBNS/SWCNT mass ratio of 7.5%. Finally, six pairs of p-type EBNS/SWCNT films and n-type copper sheets are connected in series to assemble a self-powered thermoelectric device, which demonstrates an open-circuit voltage of 8.1 mV and an output power of 550 nW under a temperature difference of 60 K. Therefore, this work provides a simple and effective method to improve the performance of carbon nanotube-based thermoelectric materials.