Increasing the thermoelectric power generated by composite films using chemically functionalized single-walled carbon nanotubes

We prepared and characterized flexible thermoelectric (TE) materials based on thin films of single-walled carbon nanotube (SWCNT) composites with polyvinylalcohol. While pristine SWCNTs incorporated in a polymer matrix generated a p-type TE material, chemical functionalization of SWCNTs by using polyethyleneimine produced an n-type TE material. TE modules made of both p- and n-type composite were fabricated to demonstrate TE voltage and power generation. A single p–n junction made of two composite strips containing 20 wt.% of SWCNTs generated a high TE voltage of 92 μV per 1 K temperature gradient (ΔT). By combining five electrically connected p–n junctions an output voltage of 25 mV was obtained upon the applying ΔT = 50 K. Furthermore, this module generated a power of 4.5 nW when a load resistance matched the internal module resistance of 30 kΩ. These promising results show the potential of TE energy conversion provided by the SWCNT composite films connected in scalable modules for applications that require light weight and mechanical flexibility.