The synthesis and optoelectronic properties of highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) films prepared by vapor phase polymerization (VPP) was reported. Patterned ITO-coated glass substrates were used for OLED fabrication, which were first cleaned, and then exposed to an oxygen plasma in an Emitech K1050X plasma asher, before a PEDOT-PSS hole-injection layer. The oxidants used were based on a 0.45 μm filtered solution comprising isopropanol (IPA) with Fe(OTs)3 and pyridine. After patterning a VPP PEDOT stripe on the substrates, plasma-oxygen treatment at a range of powers for 30s, a hole-injection layer of PEDOT-PSS was spin-coated on the top. Thin film conductivities were measured using a four-point-probe system with current-voltage data. VPP PEDOT composition alters as the film grows, and suggests that the energy barrier between VPP PEDOT layer could be minimized by the use of VPP PEDOT films.