Significantly enhanced thermoelectric performance of a solution-processable organic polymer and carbon nanotube composite via molecular packing engineering

Abstract

Combining solution-processable organic polymers and carbon nanotubes (CNTs) with excellent electrical conductivity has been demonstrated to be an effective strategy to elevate thermoelectric performance. Nevertheless, the seriously inadequate attention given to constructing superior polymers and the ambiguous correlation between polymeric architectures and the thermoelectric properties of polymer/CNT composites largely impede the further improvement of thermoelectric parameters. Herein, three one-step synthetic organic polymers named BTC8, BTSC8 and BTSC12 are constructed with the same main building units but different alkyl side chains and molecular rigidity/planarity to reveal the significant structure–property relationship. The condensed alkyl chains and simultaneously enhanced rigidity/planarity could reduce electron reorganization energy, facilitate effective molecular packing and thus provide excellent charge transport channels in BTSC8/SWCNT based blend films, affording a superior power factor of 241.4 μW m⁻¹ K⁻² with satisfactory air stability compared to 188.8 and 159.7 μW m⁻¹ K⁻² for BTSC12 and BTC8 based blend films, respectively. Our work demonstrated that conjugated polymer/CNT based thermoelectric performance could be dramatically increased by balancing the trade-off between the Seebeck coefficient and electrical conductivity via molecular packing engineering such as improving molecular rigidity/planarity, reducing reorganization energy and strengthening molecular packing.