This study demonstrates the fabrication of high-performance thermoelectric carbon nanotube /poly(3-hexylthiophene) (CNT/P3HT) nanocomposite films and flexible CNT/P3HT organic thermoelectric generators (OTEGs) by spray-printing. The spray-printed few-walled CNT/P3HT nanocomposite films exhibited excellent thermoelectric properties. The Seebeck coefficient, electrical conductivity, and power factor of the nanocomposite films were 97 ± 11 µV K -1 , 345 ± 88 S cm -1 , and 325 ± 101 µW m -1 K -2 , respectively, at room temperature. We fabricated the flexible OTEG solely from p-type CNT/P3HT nanocomposite patterns sprayprinted on a polyimide substrate, and confirmed its electric power generation capabilities.
Main textThermoelectric materials have been studied extensively as clean energy-conversion materials.The performance of thermoelectric materials can be assessed by the figure of merit, ZT = S 2 σT/κ, where S, σ, T, and κ are the Seebeck coefficient, the electrical conductivity, the absolute temperature, and the thermal conductivity, respectively. As an alternative to the figure of merit, the power factor, S 2 σ, is occasionally used because precise measurement of the in-plane thermal conductivity of a film on a substrate is difficult. Recently, organic thermoelectric materials have attracted much attention because of their potential for use in flexible, light weight, and low-cost printed organic thermoelectric generators (OTEGs). 1-17 Of the various organic thermoelectric materials currently available, films of conjugated polymers such as poly(3,4-ethylenedioxythiophene) (PEDOT), polyaniline (PANI) and poly(3hexylthiophene) (P3HT) have been the most widely studied. However, the thermoelectric performance of conjugated polymer films needs to be further improved for application to OTEGs. Recently, researchers have found that carbon nanotubes (CNTs) are effective fillers for enhancing the thermoelectric performance of conjugated polymer matrices. 3-17 Grunlan et al. reported that vacuum-filtrated single-walled CNT/PEDOT:poly(styrene sulfonate) (PSS) nanocomposite films exhibited power factors of up to 140 µW m -1 K -2 at room temperature. 3 Müller et al. reported that drop-cast single-walled CNT/P3HT nanocomposite films exhibited power factors of 95 ± 12 µW m -1 K -2 at room temperature. 4 Chen et al. reported that drop-cast single-walled CNT/PANI nanocomposite films exhibited power factors of up to 176 µW m -1 K -2 at room temperature. 5 Yu et al. reported that drop-cast double-walled CNT/PANInanocomposite films exhibited power factors of ~220 µW m -1 K -2 at room temperature. 6 In another work, we reported that wire-bar-coated single-walled CNT/P3HT nanocomposite films exhibited power factors of 267 ± 38 µW m -1 K -2 at room temperature. 7 Thermoelectric CNT/conjugated polymer nanocomposite films have been fabricated by solution-processing methods, such as drop-casting and bar-coating. However, such solution-processing techniques are not suitable for application to low-cost printed OTEGs, because additional proces...
