Sequential Solution Polymerization of Poly(3,4-Ethylenedioxythiophene) Using V<Sub>2</Sub>O<Sub>5</Sub> as Oxidant for Flexible Touch Sensors

Abstract

Various in-situ synthesis methods have been developed for the polymerization of 3,4-ethylenedioxythiophene (EDOT) monomers, such as electro-polymerization (EP), oxidative chemical vapor deposition (OCVD) and vapor phase polymerization (VPP). Additional to these existing techniques, here a novel and facile method is introduced to fabricate highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films in-situ by solution means. The process contains sequential deposition of oxidants and monomers. V2O5 is introduced as the oxidant in this synthetic route. Excess reactants and by-products can be completely removed from the PEDOT film by MeOH-rinsing. The obtained PEDOT films possess good crystallinity and high doping level, with carrier concentration three orders of magnitude higher than the commercial product (PH1000, Heraeus GmbH). The electrical conductivity of the as-cast PEDOT film reaches up to 1420 S/cm. In addition, this method is fully compatible with large-scale printing techniques. A 15 cm × 12 cm PEDOT film is printed on polyethylene terephthalate (PET) substrate by bar coating. These PEDOT conducting films enable the realization of flexible touch sensors, which demonstrate superior flexibility and sensitivity. The low-cost and highly efficient synthetic method shows great potential for large-scale production of PEDOT films that have wide applications in electromagnetic shielding, antistatic coating, sensor, etc.