High thermoelectric power-factor composites based on flexible three-dimensional graphene and polyaniline

Hybrid thermoelectric (TE) nanocomposites containing conducting polymers and nanocarbon materials have been extensively studied in recent years due to their unique advantages over single-phase organic/inorganic TE materials. Nanocarbon materials have been developed as conductive nanofillers to improve the electrical conductivity of the polymer matrix, and to create a strong π-π interfacial interaction with the matrix to enhance the TE performance. However, previous designs of the hybrid TE nanocomposites tend to cause aggregation of nanocarbon materials, which is detrimental to the TE performance. Also, they are limited in their fabrication to thin film technologies with submicron thicknesses, which prevents these composites from being used in practical TE devices. Herein, we present the synthesis and thermoelectric properties of free-standing, three-dimensional graphene (3DG)-polyaniline (PANI) composites with greater than 100 μm thicknesses for high performance flexible p-type thermoelectrics. Our 3DG matrix has been synthesized by Chemical Vapor Deposition (CVD) with particulate nickel catalysts, and used as a scaffold for the polymer composites. This material provides an excellent electrical conductivity and a reasonable Seebeck coefficient along with very good mechanical integrity preserved when bending, thus making it a promising candidate for flexible TE. PANI polymer was electrochemically grown on the 3DG scaffold as a filler to further tune the TE properties. The proposed 3DG-PANI composites showed a maximum power factor of 81.9 μW m-1 K-2 with a PANI loading of 80 wt% and highly reproducible TE performance after repeated mechanical bending tests. This novel material provides a different strategy for simple and scalable fabrication of flexible thermoelectrics with high performance TE energy harvesting and improved mechanical properties.