Mesoscopic 2D Charge Transport in Commonplace PEDOT:PSS Films

Abstract

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, the existence of mesoscopic 2D coherent charge transport in poly(3,4‐ethylenedioxythiophene):poly‐(styrenesulfonate) (PEDOT:PSS) film is demonstrated by performing structural investigations and high‐field magnetoconductance (MC) measurements in magnetic fields of up to 15 T. The researchers have 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 from the viewpoint of 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 3D hopping among 2D states. These findings elucidate the hieratical nature of charge transport in the PEDOT:PSS film, which can provide new insight into a recent engineering concern, i.e., the anisotropic conductance.