Thermoelectric (TE) film has wide potential application in low-grade waste heat recovery and TE generation due to its quick response and multifunctional integration. Multi-nanocomposite is a promising method to solve the difficulty of maintaining temperature difference and achieving a high figure of merit ZT. However, the depletion layer induced by the multi-nanocomposite typically degrades performance. This study presents a simple and convenient method to solve this problem by pulse electric field (PEF). Prototypical TE Bi2 Te3 is selected as the objective film. The strong current density effect of PEF removes the depletion layer among carbon nanotubes (CNT) and Bi2 Te3 grains. Thus, the CNT nanocomposite with PEF treatment breaks the trade-off between electrical conductivity and Seebeck coefficient, achieving a power factor of 4400 µW m-1 K-2 which stabilizes after annealing effect to 2920 µW m-1 K-2 , a record for Bi2 Te3 films. Simultaneously, the self-assembled porosity decreases thermal conductivity via phonon scattering while still maintaining a high electrical conductivity of 3130 S cm-1 . Thus, the porosity helps maintain the temperature difference and thereby enables a sharp increase in output power. These results indicate that the combination of PEF and multi-nanocomposite is a new method to enhance TE performance, which would have a potential application in the commercial field.
Keywords: depletion layer; external field; multi-nanocomposites; thermoelectric films.
© 2021 The Authors. Small published by Wiley-VCH GmbH.