Mesoscopic 2D Charge Transport in Commonplace PEDOT:PSS Films

TL;DR

This study reveals mesoscopic 2D coherent charge transport in PEDOT:PSS films, linked to their nanostructure, challenging assumptions about their structural homogeneity and offering insights into their anisotropic conductance.

Contribution

It demonstrates the existence of 2D coherent charge transport in PEDOT:PSS films and connects this to their nanostructured laminated morphology, a novel insight for conducting polymers.

Findings

Positive magnetoconductance indicates 2D electronic states.

Charge transport involves mesoscopic 2D tunneling and 3D hopping.

Nanostructure underpins the 2D transport regime.

Abstract

The correlation between the transport properties and structural degrees of freedom of conducting polymers is a central concern in both practical applications and scientific research. In this study, we demonstrated the existence of mesoscopic two-dimensional (2D) coherent charge transport in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) film by performing structural investigations and high-field magnetoconductance (MC) measurements in magnetic fields of up to 15 T. We succeeded in observing marked positive MCs reflecting 2D electronic states in a conventional drop-cast film. This low-dimensional feature is surprising, since PEDOT:PSS-a mixture of two different polymers-seems to be significantly different from crystalline 2D materials in the viewpoint of the structural inhomogeneity, especially in popular drop-cast thick films. The results of the structural experiments suggest that such 2D transport originates from the nanometer-scale self-assembled laminated structure, which is composed of PEDOT nanocrystals wrapped by insulating sheets consisting of amorphous PSSs. These results indicate that charge transport in the PEDOT:PSS film can be divided into two regimes: mesoscopic 2D coherent tunneling and macroscopic three-dimensional hopping among 2D states. Our findings elucidate the hieratical nature of charge transport in the PEDOT:PSS film, which could provide new insight into a recent engineering concern, i.e., the anisotropic conductance.