Effect of solvent on carrier transport in poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) studied by terahertz and infrared-ultraviolet spectroscopy

The effect of solvent such as ethylene glycol (EG) on the carrier transport in poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS) was studied by the combination of terahertz (THz) time-domain transmission spectroscopy (0.1-3 THz) and broadband reflectance spectroscopy (4-800 THz). While the broadband reflectance showed a plasma edge in the near-infrared, the frequency dependence of the THz conductivity of PEDOT/PSS indicated weakly localized carrier behavior. The simultaneous fitting of both spectra by the localization-modified Drude model allowed us to conclude that the significant increase in conductivity with the addition of EG is due to improved carrier mobility in the PEDOT/PSS.