Enhancing thermoelectric performance of single-walled carbon nanotube/reduced graphene oxide composites with small organic molecules as a novel additive

A small organic molecule (SOM), 2,2′-(3,3′′-dihexyl-[2,2′:5′,2′′-terthiophene]-5,5′′-diyl)bis(1-octyl-1H-phenanthro[9,10-d]imidazole) (1), was utilised as an additive to intercalate with reduced graphene oxides (rGOs–1) in a single walled-carbon nanotube (SWCNT) composite. The ternary composite formed by incorporating rGOs–1 into the SWCNTs exhibited improvements in thermoelectric (TE) and carrier transport properties through the strong interfacial π–π interaction between the rGOs–1 and SWCNTs. The SOM 1 hybridised with the SWCNT composite induced significant interfacial phonon scattering, resulting in a reduction in the thermal conductivity (κ) of the SWCNT composite with rGOs–1. As a result, the SWCNT composite incorporating rGOs–1 demonstrated a simultaneous improvement of the Seebeck coefficient by 15% and a reduction in κ by 32%, resulting in an enhancement in the TE figure of merit (6.8 ± 0.7 × 10−3 at 297 K), which was 2.3 times higher than that of the SWCNTs alone (2.9 ± 0.5 × 10−3).