Enhancement Effect of the C 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 C and its derivative into polyethylenimine/single-walled carbon nanotube (PEI/SWCNT) films. The result demonstrated that the dispersity of triethylene glycol-modified C (TEG-C) was better in PEI/SWCNT films than that of pure C. Among the prepared composite films, TEG-C-doped PEI/SWCNT (TEG-C/PEI/SWCNT) films exhibited the highest TE performance, achieving a peak electrical conductivity of 923 S cm with a Seebeck coefficient of -42 μV K at a TEG-C/SWCNT mass ratio of 1:100. Compared to that of PEI/SWCNT, the power factor was increased significantly from 40 to 162 μW m K after the addition of TEG-C, which was higher than that of films after the addition of C. In addition, the n-type doped SWCNT films had good air stability at high temperatures, and the Seebeck coefficients of C/PEI/SWCNT and TEG-C/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.