Highly Conductive and Transparent Poly(3,4-ethylenedioxythiophene):p-Toluene Sulfonate Films as a Flexible Organic Electrode

Abstract

Highly transparent and conductive poly(3,4-ethylenedioxythiophene):p-toluene sulfonate (PEDOT:PTS) films were prepared by gas-phase polymerization using the chemical vapor deposition (CVD) technique for flexible organic electrodes. These conductive PEDOT:PTS films have a high transparency (up to 80%), and possess a very low sheet resistance of a 100 Ω/□ (up to 2500 S cm-1) at 150 nm thickness. Their sheet resistance attained 27 Ω/□ at 350 nm thickness with O2 plasma doping. The 1–3 mm pitched pattern can also be easily formed by plasma etching and/or the selective exposure technique of O2 plasma. This electrode film has a higher transmittance than an amorphous indium–tin oxide (a-ITO) electrode film with thickness under 120 nm, and their conductivities were comparable with the a-ITO layer. We report on the fabrication and characterization of a flexible organic light-emitting diode (OELD) using PEDOT:PTS for the electrodes. The device is demonstrated to exhibit light emission and a brightness level up to 1800 cd/m2 at 25 V.