Carrier transport of conducting polymer PEDOT:PSS investigated by temperature dependence of THz and IR spectra

In this study, we have investigated the temperature dependence of the optical conductivity of poly(3,4-ethylenedioxythiophene): poly(styrene-sulfonate) (PEDOT:PSS) films measured by the combination of THz and infrared-visible spectroscopy to understand the effect of the ethylene glycol (EG) on the carrier transport. The addition of EG to the PEDOT:PSS colloidal dispersion significantly improve the dc conductivity of PEDOT:PSS film due to the increase of the crystallinity and the change of the morphology in PEDOT:PSS films. The temperature dependences of THz conductivities was discussed using the localization modified Drude (LD) model describing the weakly localized carrier behavior and the series sequence of free and hopping carrier (SSFHC) model. LD model analysis suggests that the carrier delocalization by the addition of EG improve the carrier mobility and DC conductivity. On the other hand, SSFHC model revealed that the macroscopic carrier transport of PEDOT:PSS was dominated by the hopping conduction between PEDOT nano-crystals where the metallic transport were realized.