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Preparing stable n-type flexible single-walled carbon nanotube (SWCNT)-based thermoelectric films with high thermoelectric (TE) performance is desirable for self-powering wearable electronics but remains a challenge. Here, the interface regulation and thermoelectric enhancement mechanism of ferrocene derivatives on polyethylenimine/single-walled carbon nanotube (PEI/SWCNT) composite films have been explored by doping ferrocene derivatives (f-Fc–OH) into PEI/SWCNT films. The results show that the introduction of f-Fc–OH leads to the formation of “thorn” structures on the surfaces of SWCNT bundles via hydrophilic and hydrophobic interactions, the generated energy-filtering effect improves the thermoelectric properties of the PEI/SWCNT film, and the f-Fc–OH-doped PEI/SWCNT (f-Fc–OH/PEI/SWCNT) achieves the highest room-temperature power factor of 182.22 ± 8.60 μW m–1K–2with a Seebeck coefficient of −64.28 ± 0.96 μV K–1and the corresponding ZTvalue of 4.69 × 10–3. The Seebeck coefficient retention ratio of the f-Fc–OH/PEI/SWCNT nearly remained 68% after being exposed to air for 3672 h, while the PEI/SWCNT film changed from n-type to p-type after being exposed to air for about 432 h. In addition, the temperature-dependent thermoelectric properties show that the f-Fc–OH/PEI/SWCNT achieves a high power factor of 334.57 μW m–1K–2at 353 K. Finally, a flexible TE module consisting of seven pairs of p–n junctions is assembled using the optimum composite film, which produces an open-circuit voltage of 42 mV and a maximum output power of 4.32 μW at a temperature gradient of 60 K. Therefore, this work provides guidance for preparing stable n-type SWCNT-based composite films with enhanced thermoelectric properties, which have potential applications in flexible generators and wearable electronic devices.

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 C60and 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–1with a Seebeck coefficient of −42 μV K–1at 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–1K–2after 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.