Single-walled carbon nanotubes (SWCNTs)/organic small molecules (OSMs) are promising candidates for application in thermoelectric (TE) modules; however, the development of n-type SWCNT/OSMs with high performance is lagging behind. Only a few structure−activity relationships of OSMs on SWCNT composites have been reported. Recently, we find that the n-type acridone/SWCNT composites display high power factor (PF) values at high temperature but suffer from low PFs at room temperature. Here, the performance of SWCNT composites containing an acridine derivative (AD) as well as its analogues with different counterions (Cl − , SO 4 2− and F − ) and lengths of alkyl chains (ADLA1−2 and ADLA4−5) is reported. Among the composites, SWCNT/ADLA4 with no counterions exhibits the highest PF value of 195.2 μW m −1 K −2 at room temperature, which is 4.9 times higher than that of SWCNT/ADTAd (39.8 μW m −1 K −2 ), indicating that the acridine scaffold and the lengths of alkyl chains contribute to the dramatic changes in the TE performance. In addition, SWCNT/ADLA4 exhibits high PF values at all the temperatures we investigate, which range from 154.7 to 230.7 μW m −1 K −2 . Furthermore, a TE device consisting of five pairs of p (the pristine SWCNTs)−n (SWCNT/ADLA4) junctions is assembled, generating a relatively high open-circuit voltage (41.7 mV) and an output power of 1.88 μW at a temperature difference of 74.8 K. Our results suggest that structural modifications might be an effective way to advance the development of TE materials.

Single-walled carbon nanotubes (SWCNTs) are desirable flexible thermoelectric materials in applications of large-scale low-grade thermal energy. However, weak Seebeck coefficients of SWCNTs around room temperature limit their development as a flexible power generator. In this work, we significantly improve the Seebeck coefficients of SWCNT-based composites by integrating the discotic liquid-crystal 2,3,6,7,10,11-hexakis(hexyloxy) triphenylene (HAT6) through the energy-filtering effect. The Seebeck coefficients of SWCNT/HAT6 composite films are about more than twice that of the pristine SWCNT films, and a maximum power factor of 408.23 ± 48.96 μW m −1 K −2 is achieved at room temperature, which is one of the highest values among organic small-moleculebased thermoelectric composites reported so far. The flexible power generator based on p-type SWCNT/HAT6 films is first assembled. An outstanding power density of 0.64 μW cm −2 with a thermoelectric voltage of 17.64 mV at a temperature gradient of 56 K is achieved. This study demonstrates that SWCNT/ discotic liquid-crystal composites show great promise in thermoelectric (TE) materials and open a new avenue for the development of TE devices.

Introducing two-dimensional (2D) conjugated structures to polymers is a feasible way for the design of functionalized polymers due to their good planarity, high electron/hole mobility, thermal stabilities, and so forth. However, the current development of thermoelectric polymers is mainly restricted to the limited modification of the one-dimensional conjugated polymers. Herein, a novel donor−acceptor based 2D conjugated polymer, P(BDTTT-DPP), was designed and synthesized for the enhancement of thermoelectric properties. Compared to the onedimensional conjugated polymer P(BDT-DPP), P(BDTTT-DPP) showed a higher doping level when doped with the p-type FeCl 3 dopant. After doping with 20 mg/mL FeCl 3 for 15 min, the optimal power factor of P(BDTTT-DPP) was obtained to be 6.50 μW m −1 K −2 at room temperature, which is 26 times higher than that of P(BDT-DPP). The studies of film morphology and packing structure analysis further indicated that the π−π stacking (010) distance of P(BDTTT-DPP) was maintained after the doping process, and the longer lamellar stacking distance allowed the FeCl 3 dopants to efficiently incorporate between the lamellar domains compared to that of P(BDT-DPP), which is favorable to the crystallinity and electron transferability. The results of our work provide valuable insights into the development of donor−acceptor based 2D conjugated polymer for high-performance organic thermoelectric materials.

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