Field-effect and chemical charge-type modulations of carbon nanotubes using functional polymers for thermoelectric energy harvesters

As devices continue to shrink in size and grow in abundance, power supply methods using clean and abundant materials become increasingly important. Single-walled carbon nanotubes (SWCNTs) are promising materials as the thermoelectric (TE) energy-harvesting candidate due to their flexibility, nontoxicity, and relatively large TE power factors. This paper reviews our current studies on the charge-type conversion of SWCNTs for readily pairing several p- and n-type SWCNTs to improve the TE voltage output. First, we describe the polarity tuning of SWCNTs by electric dipoles of ferroelectric polymer. The sign of Seebeck coefficient of SWCNTs could be tuned by the direction of the electric dipoles adjacent to nanotubes in the ferroelectric-gate field-effect transistor-like device configuration. Second, we demonstrate the electron doping into SWCNTs by several versatile polymer-dopant charge transfer. The obtained negative Seebeck coefficients of SWCNTs were correlated to the highest occupied molecular orbital energy levels of the dopant polymers. Our findings enables the direct use of low-temperature waste heats around dwelling environments using eco-friendly materials and techniques.