Towards a transparent, highly conductive poly(3,4-ethylenedioxythiophene)

Abstract

A detailed investigation of the processing parameters influencing the oxidative polymerization of 3,4-ethylenedioxythiophene (EDOT) and a methanol-substituted derivative (EDOT-CH₂OH) was performed with the goal of maximizing the conductivity of the polymer. We show that the conductivity can be significantly enhanced by varying the monomer, oxidant (iron(III) p-toluenesulfonate (Fe(OTs)₃)), weak base (imidazole (Im)), solvent (various alcohols), and solution concentrations. The effect of each variable on the final materials properties is investigated, and the parameters have been optimized to achieve conductivities as high as 900 S cm⁻¹. Surface resistance below 150 Ω/□ for 80-90 nm thick films with visible-spectrum transparency exceeding 80 % is achieved. The combination of these properties makes the films highly suitable for numerous device applications.