Sequential Doping of Carbon Nanotube Wrapped by Conjugated Polymer for Highly Conductive Platform and Thermoelectric Application

Abstract

Doping of conjugated polymers (CPs) is a promising strategy to obtain solutionprocessable and highly conductive films; however, the improvement in electrical conductivity is limited owing to the relatively poor carrier mobility of CPs. Herein, a CP with excellent molecular doping ability, i.e., poly[2-([2,2 '-bithiophen]-5-yl)3,8-difluoro-5,10- bis(5-octylpentadecyl)-5,10-dihydroindolo[3,2-b]indole] (PIDFBT) is wrapped onto the surface of single-walled carbon nanotubes (SWCNTs). The resulting PIDF-BT@SWCNT simultaneously achieves excellent solution dispersibility and a high electrical conductivity of over 5000 S cm(-1) through AuCl3 doping. The doping mechanism is systematically studied using spectroscopic analysis, and the four-probe field-effect transistor based on the doped PIDF-BT@SWCNT confirms a carrier mobility up to 138 cm(2) V-1 s(-1). The carriertransfer barrier energy is related to the Schottky barrier between the SWCNT and PIDF-BT, which can be controlled by doping. Finally, when the doped PIDFBT@SWCNT is applied to a thermoelectric device, a power factor exceeding 210 mu Wm(-1) K-2 is achieved because of its high electrical conductivity, even if the increased carrier density reduces the Seebeck coefficient.