Structural origin of anisotropic transport in electrically conducting dichloroacetic acid-treated polymers

The post-deposition treatment of water-processable, polymer acid-templated conducting polymers with dichloroacetic acid has recently been shown to enhance in-plane conductivity by orders of magnitude. Here, we evaluate both the in-plane and out-of-plane conductivities of dichloroacetic acid-treated conducting polymer films, and track the accompanying evolution of film structure and composition. Films of poly(ethylene dioxythiophene)-poly(styrene sulfonic acid), PEDOT-PSS, exhibit improvements in both in-plane and out-of-plane conductivities following dichloroacetic acid treatment, associated with the removal of excess PSS from the surface. Conversely, polyaniline-poly(2- acrylamido-2-methyl-1-propanesulfonic acid), PANI-PAAMPSA, films are characterized by high anisotropies in conductivity, with the in-plane conductivity being orders of magnitude higher following DCA treatment and the out-of-plane conductivity substantially lower after the same treatment. Our experiments indicate that this unusual electrical anisotropy results from a vertically inhomogeneous composition profile.