Enhanced electrical properties of PEDOT:PSS films using solvent treatment and its application to ITO-free organic light-emitting diodes

Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) films are prepared by introducing a new solvent 2-ethoxyethanol and are optimized by acid-free solvent post treatment. The behavior of samples are investigated with various coating conditions. The change of electrical performance for 2-ethoxyethanol added PEDOT:PSS films with various post treatment methods is studied. Upon post treatment, the sheet resistance greatly decreases attributed to a structural change with removal of insulating PSS in the film. Based on these conductive films, we demonstrate efficient ITO-free green phosphorescent organic light-emitting diodes (OLEDs). The efficiency of OLEDs with post-treated PEDOT:PSS electrodes is greater than that of OLEDs with untreated PEDOT:PSS electrodes. The results illustrate a promising future for flexible, low-cost, ITO-free OLEDs employing PEDOT:PSS electrodes optimized by 2-ethoxyethaol with acid-free solvent post treatment.