A facile process to produce highly conductive poly(3,4-ethylenedioxythiophene) films for ITO-free flexible OLED devices

Abstract

A facile vapor phase polymerization (VPP) method is carried out to fabricate highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) flexible films with a low concentration FeCl₃ ethanol solution as the oxidant, without high temperature, vacuum conditions and additives. Three kinds of PEDOT morphologies (square-like, flower-like and flat) can be observed on the surface of the films and the appearance of the square-like and flower-like structures does not affect the transparency of the films. A ca. 1500 S cm⁻¹ film conductivity is achieved and after dipping in a H₂SO₄ solution, the conductivity significantly increases to ca. 2200 S cm⁻¹ with a sheet resistance down to 50 Ω □⁻¹ and a transparency in the visible spectrum of >80% at 90 nm thickness. In addition, a simple ITO-free flexible OLED device was designed with a VPP–PEDOT film as the anode which was able to maintain a stable luminance after various kinds of bending and showed the feasibility of substituting PEDOT for the ITO layer in flexible OLED devices. The facile way offers an effective and convenient strategy to fabricate highly conductive PEDOT films and represents a significant step forward in the manufacture of flexible OLED devices and flexible displays in the rapidly growing organic electronics arena.