Synergistic effect of sequential solvent treatment on the structural and low temperature charge transport of PEDOT:PSS films

Abstract

A detailed study on the low temperature charge transport and magnetoresistance (MR) measurements of spin-coated and solvent treated poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) films has been presented. The samples were prepared by sequential treatment of PEDOT:PSS film using dimethyl sulfoxide and sulphuric acid. X-ray diffraction and Raman spectroscopy elucidate the effect of solvent treatment on the structural modifications of the film, which correlates to the enhanced conductivity values. The nature of solvent and the sequence of successive treatments using different solvents has been effectively utilized to tune the conductivity of the film over a wide range. Further, the low temperature (300–2 K) charge transport study indicates that the resistance of the film rises sharply below 50 K, which implies the samples lie in the category of disordered materials. A linear fit of ln R vs. T −1/4 for all the samples indicates that the temperature dependent resistance of solvent treated PEDOT:PSS films follow 3D variable range hopping model. The observed large positive MR behavior of the films has been discussed in terms of the wave function shrinkage of the charge carriers. The MR follows ∼B 2 and ∼B 1/3 dependence at low and high magnetic field regimes, respectively. The sequential treatment of PEDOT:PSS films shown in the present study is an effective method to enhance the electrical conductivity significantly.