Solvent-doped PEDOT:PSS: Structural transformations towards enhanced electrical conductivity and transferable electromagnetic shields

Abstract

The enhanced electrical conductivity of solvent-doped poly(3,4-ethylenedioxythiophene): poly(styrene sulfonate) (PEDOT:PSS) is attributed to the screening effect between PSS and PEDOT chains. Yet, the precise manner in which this effect influences the crystalline structure and conformation of PEDOT:PSS remains unclear. In this study, we utilize Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and Grazing-incidence wide-angle X-ray scattering (GIWAXS) to examine the conformational changes and two-dimensional (2D) crystalline structure of PEDOT:PSS when doped with a variety of solvents, including dimethyl sulfoxide (DMSO), ethylene glycol (EG), dimethylformamide (DMF), methanol (MeOH), ethanol (EtOH), tetrahydrofuran (THF), and acetone. Our observations unveil that solvent doping improves the electrical conductivity of PEDOT:PSS by modifying its crystalline structure. This alteration leads to reduced inter-lamellar (d200) and π-π stacking (d010) distances, facilitating the formation of densely packed and well-ordered PEDOT crystallites in both face-on and edge-on orientations. Moreover, this doping process enhances the transferability and mechanical properties of drop-casted films, resulting in a flexible and transferable electromagnetic interference (EMI) shield with exceptional total shielding effectiveness (SET) of 35.70 dB and specific shielding effectiveness (SSE/t) of 7105.34 dB cm2.g−1.