The synthesis of high conductivity poly (3,4-ethylenedioxythiophene) (PEDOT) films using vacuum vapour phase polymerisation is reported. Water vapour is introduced into the chamber and results suggest that it acts as a proton scavenger during polymerisation. Process optimisation leads to PEDOT films that have high conductivity and a blue-black appearance. Poor quality films have lower conductivity and a characteristic greenish colour. UV-vis-NIR spectra show that poor PEDOT films are characterised by higher absorption in the UV-vis region and an absorption plateau in the NIR region, which suggests an increased level of disrupted conjugation along the polymer backbone or higher oligomer content. Conversely, high quality PEDOT is characterised by an extended NIR absorption tail and lower absorption in the UV-vis region.