Boosting the Power Factor of Benzodithiophene Based Donor–Acceptor Copolymers/SWCNTs Composites through Doping

Abstract

<jats:p>In this study, a benzodithiophene (BDT)-based donor (D)–acceptor (A) polymer containing carbazole segment in the side-chain was designed and synthesized and the thermoelectric composites with 50 wt % of single walled carbon nanotubes (SWCNTs) were prepared via ultrasonication method. Strong interfacial interactions existed in both of the composites before and after immersing into the 2,3,5,6-Tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ) solution as confirmed by UV-Vis-NIR, Raman, XRD and SEM characterizations. After doping the composites by F4TCNQ, the electrical conductivity of the composites increased from 120.32 S cm−1 to 1044.92 S cm−1 in the room temperature. With increasing the temperature, the electrical conductivities and Seebeck coefficients of the undoped composites both decreased significantly for the composites; the power factor at 475 K was only 6.8 μW m−1 K−2, which was about nine times smaller than the power factor at room temperature (55.9 μW m−1 K−2). In the case of doped composites, although the electrical conductivity was deceased from 1044.9 S cm−1 to 504.17 S cm−1, the Seebeck coefficient increased from 23.76 μV K−1 to 35.69 μW m−1 K−2, therefore, the power factors of the doped composites were almost no change with heating the composite films.</jats:p>

Pseudo in situ construction of high-performance thermoelectric composites with a dioxothiopyrone-based D–A polymer coating on SWCNTs

“…[5][6][7][8][9][10][11][12] In this respect, conducting polymers/carbon nanotube (CNT) composites have demonstrated tremendous progress. [13][14][15][16][17][18][19][20][21][22] Currently, TE performance optimization of the polymer/CNT composites are concentrated on two aspects including the molecular design of polymers and the preparation technology.…”

“…13,14 The other is the drop-casting of a mixed suspension of the pre-prepared polymers and SWCNTs, which is suitable for those polymers that are structurally complicated and synthetically strict (such as water-free and oxygen-free conditions). [16][17][18][19][20][21][22] Although many other lm-forming technologies, such as dip-coating, 23 spray-coating 24 and spin-coating, 25 were used for fabricating TE samples, almost all the recentlydeveloped complicated TE polymer/CNT composites have been prepared through the direct drop-casting. However, the drop-casting method is difficult to form uniform interface coating layer of polymers on the surface of SWCNTs because of the rapid evaporation of solvents and static growth of polymers on the substrate, leading to conglutination and lling of the precipitated polymer in the gap of SWCNT networks.…”

“…In the past years, a number of new structural segments and special bonding modes were used for construction of more structurally complicated polymers than the classical polymers, and those conducting polymers were employed to form the composites with superior TE performances. [15][16][17][18][19][20][21][22] In 2016, our group reported a kind of poly-Schiff base/SWCNT TE composites and the chelation effect of the Schiff base with transition metal ions on the TE performance. 15 Subsequently, Wang et al prepared a series of TE composite lms based on SWCNTs and bipyridine-containing polyuorene derivatives, discussing the variation trend of TE performance caused by chelation of the bipyridine unit with various metal ions.…”

“…Both power factors reached about 60 mW m À1 K À2 before and aer doping composites with F4TCNQ at room temperature. 22 Despite these advances, the structural types of conjugated polymers for TE composites are still extremely limited and their TE performances remain far below the expected level. Apparently, it would be very meaningful to develop novel types of conjugated polymers and efficient compositing method for TE composite materials.…”

“…Both power factors reached about 60 μW m −1 K −2 before and after doping composites with F4TCNQ at room temperature. 22 …”