Charge transport in cross-linked PEDOT:PSS near metal–insulator transition

Abstract

The charge transport in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) cross-linked with divinyl sulfone (c-PEDOT:PSS) is compared with pristine PEDOT:PSS from conductivity, electric field, and frequency studies. In a cross-linked sample, the room temperature conductivity increased from 0.8 to 630 S/cm. The temperature dependence of conductivity, down to 4.2 K, is significantly weakened in a cross-linked sample. This cross-linking induced metal–insulator transition in PEDOT:PSS, as inferred from conductivity ratios [Formula: see text], shows the role of modified nanomorphology in charge transport. The values of [Formula: see text] for PEDOT:PSS and c-PEDOT:PSS are 6441 and 4.6, respectively. The temperature dependence of the electric-field effect on conductivity indicates that the nanoscale barriers for transport have been substantially reduced by cross-linking. Impedance spectroscopy studies suggest that the relaxation frequency in c-PEDOT:PSS is shifted to a higher frequency, and the real part decreases sharply at higher frequencies, indicating enhanced connectivity and weakened barriers between conductive PEDOT regions.