Carrier transport in conducting polymer PEDOT: PSS thin films investigated by THz-TDS and broadband reflectance spectroscopy

The effect of solvent on the carrier transport in poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) was studied by the combination of THz time-domain transmission spectroscopy (0.1-3 THz) and the 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 the weakly localized carrier behavior. The simultaneous fitting of both spectra by the localization modified Drude model allowed us to conclude that the significant increase of conductivity by adding ethylene glycol was quantitatively explained by the improvement of the carrier mobility in the PEDOT/PSS.