Mesoscopic 2D Charge Transport in Commonplace PEDOT:PSS Films

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 reduction of the out-of-plane conductance.Conductive polymers are becoming indispensable in both scientific research and practical applications because of their advantageous features, such as mechanical flexibility, low toxicity, and the potential for use in low-cost device fabrication via printing processes. In particular, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS, which is produced by doping PEDOT with PSS) is one of the most commonly used polymers owing to its beneficial electric and thermoelectric properties, good stability under ambient conditions, and visible-light transmittance in thin-film form.[1-8] Electrical conductivities exceeding 1000 S/cm have routinely been achieved through the development of efficient methods, in particular, the addition of polar solvents to aqueous PEDOT:PSS solutions; [9][10][11] however, the charge transport mechanism is still not well understood in spite of its widespread utilization. The electrical properties of PEDOT:PSS films are strongly related to their complicated macromolecular structures; hence, clarifying the correlations between their electrical and structural properties is an active area of investigation in polymer science.The anisotropic conductance, namely, the reduction of outof-plane conductivity, in highly conductive PEDOT:PSS films is one of the crucial issues that must be unraveled for future applications. [12][13][14][15][16][17] Previous studies have indicated that the out-of-plane conductivity tends to be significantly less than the in-plane conductivity. Nardes et al. [12] reported an anisotropy...

A tied Fermi liquid to Luttinger liquid model for the explanation of nonlinear transport in conducting polymers

“…4c, extracted from several device features, we obtain 2. shown in Supplementary Fig. 5, and also corresponding to the reported values in the same system characterized by electron spin resonance (ESR) 28 .…”

“…The coupling strength between the quasi-1D chains might finally determine the dimensionality of the carriers by introducing interchain' charge delocalization. In previous works, 2D or 3D electron behaviors have been widely observed in semicrystalline doped polymers based on the Hall effect, weak localization (WL) effect 26,27,28 , etc., provided by crystalline grains.…”

Role of the Processing Solvent on the Electrical Conductivity of PEDOT:PSS

“…Among various strategies, polar solvents addition and post‐treatment are among the most used and most efficient ways to improve PEDOT:PSS electrical conductivity. [ 1,5–8 ] Both processes can induce different effects on PEDOT:PSS thin films, such as π–π stacking distance shortening (i.e., increased π–π orbital overlap), alteration of the crystallite orientation (face‐on vs edge‐on), overall crystallinity increase, PSS removal, and phase separation. [ 9,10 ] Polar solvents with high dielectric constants and high boiling points are common additives and post‐treatment agents, especially DMSO and EG (ethylene glycol).…”

A PSS‐Free PEDOT Conductive Film Supported by a Hierarchical Nanoporous Layer Glass

“…However, this conductivity is less than recently reported highly conductive PEDOT‐based films: crystalline PEDOT films (5000 S cm −1 ) and structurally optimized “metallic” PEDOT/PSS thick films (700 S cm −1 ), for example. Though the PEDOT was assumed to occupy the whole area of HNL in the above estimation, the PEDOT volume should be much less than the assumption due to following two reasons.…”

“…Furthermore, the microscopic optimizations adopted in the studies mentioned above have not been carried out in this study. Hence, we think that the PSS‐free PEDOT developed in this work is still open to conductivity improvement.…”