Enhanced thermoelectric performance by constructing PEDOT:PSS/graphene quantum dots/single-walled carbon nanotube multilayer films

Abstract

Flexible thermoelectric materials are important as self-powered systems in wearable and flexible thermoelectric devices; to this end, using single-walled carbon nanotubes (SWCNTs) is advantageous for enhancing the overall thermoelectric performance. In this study, to further enhance the thermoelectric properties of SWCNTs and overcome the weak interfacial interaction between hydrophilic poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) and hydrophobic pristine SWCNTs, a graphene quantum dots (GQDs) intermediate layer is used to couple PEDOT:PSS and SWCNTs. Multilayer films comprising PEDOT:PSS, GQDs, and SWCNTs are constructed and prepared by successively drip-coating the GQDs and PEDOT:PSS on the SWCNTs film surface. Analysis of the interfacial morphology reveals that the hydrophilic GQDs improve interfacial adhesion between PEDOT:PSS and the SWCNTs. Compared to a PEDOT:PSS/SWCNT bilayer film, the electrical conductivity of the PEDOT:PSS/GQDs/SWCNT multilayer films is enhanced, while the Seebeck coefficient is slightly lower. Meanwhile, the thermal conductivity is significantly decreased due to the increased interfacial phonon scattering. The minimum in-plane thermal conductivity for the PEDOT:PSS/GQDs/SWCNT films is 7.4 W‧m−1‧K−1, resulting in an enhanced figure of merit of 1.96 × 10−3 at 298 K. Thus, the GQDs intermediate layer is beneficial for coupling PEDOT:PSS and SWCNTs layers. The strategy employed herein offers novel insights into the preparation of high-performance SWCNTs-based thermoelectric materials.