Enhancement of Charge Transport in Polythiophene Semiconducting Polymer by Blending with Graphene Nanoparticles

Abstract

This paper describes a study on the charge transport in a composite of liquid‐exfoliated graphene nanoparticles (GNPs) and a polythiophene semiconducting polymer. While the former component is highly conducting, although it consists of isolated nanostructures, the latter offers an efficient charge transport path between the individual GNPs within the film, overall yielding enhanced charge transport properties of the resulting bi‐component system. The electrical characteristics of the composite layers were investigated by means of measurements of time‐of‐flight photoconductivity and transconductance in field‐effect transistors. In order to analyze both phenomena separately, charge density and charge mobility contributions to the conductivity were singled out. With the increasing GNP concentration, the charge mobility was found to increase, thereby reducing the time spent by the carriers on the polymer chains. In addition, for GNP loading above 0.2 % (wt.), an increase of free charge density was observed that highlights an additional key role played by doping. Variable‐range hopping model of a mixed two‐ and three‐dimensional transport is explained using temperature dependence of mobility and free charge density. The temperature variation of free charge density was related to the electron transfer from polythiophene to GNP, with an energy barrier of 24 meV.

Molecular Orientations at Buried Conducting Polymer/Graphene Interfaces

“…Extensive research has been performed to use graphene in OFET applications and to study the effective interactions between graphene and semiconducting conjugated polymers in such applications. − Among the examined semiconducting polymers, poly­(3-alkylthiophene)­s (PTs) with alkyl side chains at the 3-position of the thiophene ring have been widely studied in the graphene-conjugated polymer systems. PTs can serve as an active layer (ATL) in the system due to their high field-effect mobility, outstanding stability, and excellent solution processability.…”