Origin of different electrical conductivities in PEDOT:PSS

Abstract The different grades of poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) (Clevios P, PH500, and PH1000) were investigated to clarify the origin of the different electrical conductivities using X-ray photoelectron spectroscopy, dynamic light scattering, reflectance spectroscopy, X-ray diffraction, conductive atomic force microscopy, and Raman spectroscopy. The electrical conductivity (σ), crystallinity (X c), and carrier mobility (μ) increased in the order of Clevios P, PH500, and PH1000, whereas the composition ratio (α) and carrier density (N c) were almost the same. The results allowed us to conclude that the mechanism of different σ in the PEDOT:PSS lay in μ, where high X c with large size (D nc) and number (N nc) of PEDOT nanocrystals uniformly distributed within the PSS matrix favored carrier transport between adjacent nanocrystals, resulting in high σ in the bulk state.