A series of poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) composite thin films with prescribed concentrations of poly(ethylene glycol) were prepared. The PEDOT-PSS pristine film and PEDOT-PSS/PEG films were studied using four-probe method, photoelectron spectroscopy and atomic force microscopy. The electrical conductivity of PEDOT-PSS/PEG hybrid films was found to be enhanced compared to the PEDOT-PSS pristine film, depending on the PEG concentration and molecular weight. XPS analysis and AFM results showed that PEG induces the phase separation between the PEDOT-PSS conducting particles and the excessive PSSNa shell. Simultaneously PEG may form hydrogen bond with sulfonic groups of PSSH, and hence weaken the electrostatic interactions between PEDOT cationic chains and PSS anionic chains. These resulted in the creation of a better conduction pathway among PEDOT-PSS particles, attributed to the improvement of conductivity. (c) 2005 Elsevier B.V. All rights reserved.