Mesoscopic 2D Charge Transport in Commonplace PEDOT:PSS Films

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.