Characterizing Annealing Effect of Poly (3,4-ethylenedioxythiophene) Polymerized with Poly (4-styrenesulfonate) Conjugated Film on the Molecular Arrangement and Work Function by Core-Level and Valence-Level Band Spectra

Abstract

The poly (3,4-ethylenedioxythiophene) polymerized with poly (4-styrenesulfonate) (PEDOT:PSS) and multi walled carbon nanotube (MWNT)/PEDOT:PSS films were prepared on silicon oxide substrate using spin-coating method. The work function changes of PEDOT:PSS and MWNT/PEDOT:PSS films as a function of annealing temperature were investigated using self-modified ultraviolet photoemission spectroscopy (UPS) equipment, which is connected with ultra high vacuum (UHV) heating stage. Therefore, the annealing effect on work-function change of PEDOT:PSS film (and MWNT/PEDOT:PSS film) were specifically analyzed by minimizing the contamination-effect from reactive gases. Work functions of PEDOT:PSS and MWNT/PEDOT:PSS films were slightly increased by similar to 0.1 eV after annealing process at low temperature of 130 degrees C owing to reduction of contamination including carbon and oxygen, then gradually decreased after annealing process at high temperature due to the rearrangement of PEDOT and PSS at surface region. The molecular ratio or arrangement of PEDOT and PSS at surface region are crucial factors to determine work function and conductivity of PEDOT:PSS and MWNT/PEDOT:PSS films. Therefore, the transition behaviors of them as a function of annealing temperature were investigated by analyzing the core-level and valence band spectra of as-deposited and annealed PEDOT:PSS and MWNT/PEDOT:PSS films using X-ray photoelectron spectroscopy and UPS, respectively. (C) 2012 The Electrochemical Society. All rights reserved.