Hole Doping in Polythiophenes Encapsulated in Semiconducting and Metallic Single-Walled Carbon Nanotubes: Impact of the Electronic Structure

Abstract

Polythiophene (PT) without bending or torsion is an ideal candidate for one-dimensional conductive wires. The synthesis of PT molecules has been attempted using one-dimensional confined spaces in single-walled carbon nanotubes (SWNTs). However, carrier doping in encapsulated PT for achieving high transport properties is challenging. Herein, we investigated hole doping in PT molecules encapsulated in semiconducting and metallic SWNTs. It was found that the spectral weight ratio of the near-infrared to visible absorption band of doped PT molecules is larger in semiconducting SWNTs than that in metallic SWNTs. This result indicates that hole concentration in PT molecules is higher in semiconducting SWNTs, which is explained by the smaller number of electrons that must be removed from the SWNTs until the occurrence of hole doping in the PT molecules. This study provides an insight into the impact of the electronic structure of the surrounding materials on the carrier doping in encapsulated PT.