Enhancement Effect of the C60 Derivative on the Thermoelectric Properties of n-Type Single-Walled Carbon Nanotube-Based Films

Obtaining air-stable and high-performance flexible n-type single-walled carbon nanotube (SWCNT)-based thermoelectric films used in wearable electronic devices is a challenge. In this work, the microstructure and thermoelectric properties of n-type SWCNT-based films have been optimized via doping C60 and its derivative into polyethylenimine/single-walled carbon nanotube (PEI/SWCNT) films. The result demonstrated that the dispersity of triethylene glycol-modified C60 (TEG-C60) was better in PEI/SWCNT films than that of pure C60. Among the prepared composite films, TEG-C60-doped PEI/SWCNT (TEG-C60/PEI/SWCNT) films exhibited the highest TE performance, achieving a peak electrical conductivity of 923 S cm-1 with a Seebeck coefficient of -42 μV K-1 at a TEG-C60/SWCNT mass ratio of 1:100. Compared to that of PEI/SWCNT, the power factor was increased significantly from 40 to 162 μW m-1 K-2 after the addition of TEG-C60, which was higher than that of films after the addition of C60. In addition, the n-type doped SWCNT films had good air stability at high temperatures, and the Seebeck coefficients of C60/PEI/SWCNT and TEG-C60/PEI/SWCNT at 120 °C were still negative and remained at 92% and 85%, respectively, after 20 days. Furthermore, a flexible TE device consisting of five pairs of p-n junctions was assembled using the optimum hybrid film, which generated a maximum output power of 3.6 μW at a temperature gradient of 50.2 K. Therefore, this study provides a facile way to enhance the thermoelectric properties of n-type carbon nanotube-based materials, which have potential application in flexible power generators.