Thermoelectric Composites of Single-Walled Carbon Nanotubes with Long-Alkylphenyl-Substituted 2,6- <i>bis</i> (4-Octylphenyl)thieno[2′,3′:4,5]thieno[3,2- <i>b</i> ]thieno[2,3- <i>d</i> ]thiophene

Composites of organic small molecules (OSMs) with single-walled carbon nanotubes (SWCNTs) have attracted considerable attention in thermoelectrics, because of their intrinsic flexibility and tunable energy levels. In this work, thieno[2',3':4,5]thieno[3,2-<i>b</i>]thieno[2,3-<i>d</i>]thiophene (TTA)-based OSMs including 2,6-bis(benzo[<i>b</i>]thiophen-2-yl)thieno[2',3':4,5]thieno[3,2-<i>b</i>]thieno[2,3-<i>d</i>]thiophene (2BT-TTA), 2,6-bis(benzo[<i>b</i>]furan-2-yl)thieno[2',3':4,5]thieno[3,2-<i>b</i>]thieno[2,3-<i>d</i>]thiophene (2BF-TTA), and 2,6-bis(4-octylphenyl)thieno[2',3':4,5]thieno[3,2-<i>b</i>]thieno[2,3-<i>d</i>]thiophene (2(C₈Ph)-TTA) were designed and synthesized to construct flexible thermoelectric films. The modulation of molecular energy levels in 2(C₈Ph)-TTA facilitates effective p-type doping, while the alkylphenyl side chains enhance intermolecular π-π interactions with SWCNTs, synergistically improving the thermoelectric performance of the composite films. The optimized composite film containing 10 wt % 2(C₈Ph)-TTA exhibited the best thermoelectric performance, achieving a power factor of 372.66 ± 4.12 μW m^-1 K^-2 at room temperature, along with high thermal stability and flexibility. Furthermore, a thermoelectric generator consisting of seven pairs of p-n legs of this composite and n-type SWCNT film generates a maximum power density output of 26.64 μW g^-1 at Δ<i>T</i> = 60 K. This study provides new insights into the design of high-performance OSM/SWCNT thermoelectric materials.