Optimized Electrical Conductivity of PEDOT Thin Films and Development of oxidative Chemical Vapor Deposition using Volatile Liquid Oxidants

Conducting polymers have gained attention due to their metal-like conductivity, transparency, and flexibility. The texture and nano-structure of conducting polymers play a crucial role in their performance in technological applications. By controlling parameters such as orientation, stacking distance, crystallite size, and couplings, the charge carrier mobility can be improved. Oxidative chemical vapor deposition (oCVD) is being explored as a scalable technique for fabricating conducting polymers with characteristics such as conformal coatings, low-temperature processing, solvent-free synthesis, and mechanical flexibility. oCVD is a powerful method that allows simultaneous polymerization, doping, and thin-film formation, even on nanostructured materials. In the oCVD process, a monomer vapor, such as 3,4-ethylene dioxythiophene (EDOT), is introduced into a vacuum chamber along with an oxidant vapor. Commonly, vapor iron (III) chloride is used as the oxidant, which requires a postdeposition rinsing step to remove unreacted oxidants and oxidation by-products. Alternatively, more volatile oxidants like Br2, VOCl3, or SbCl5 can be used in a true single-step, all-dry oCVD synthesis. By controlling the π–π stacking distance and interchain charge transfer integral, highly face-on oriented semicrystalline poly(3,4-ethylenedioxythiophene) (PEDOT) thin films with metallic conductivity at low temperatures have been developed.