Effects of interfacial modification for vapor phase polymerized PEDOT on glass substrate

Optically transparent and highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were grown through vapor phase polymerization on (3-Mercaptopropyl)trimethoxysilane functionalized 3,4-Ethylenedioxythiophene (MPTMS functionalized EDOT) grafted glass substrates. Compared to bare glass, the EDOT grafted surface led to enhancements in both electrical conductivity and adhesion of PEDOT thin films. A quinoid-rich structure with increased crystallinity and a further enhanced conductivity was induced by post-deposition sulfuric acid doping. X-ray diffraction showed different orientations of the PEDOT crystals grown on substrates with and without EDOT grafting. The highest conductivity of 2690 S/cm, with an average optical transmittance of 95.4 % in the visible range, was achieved when PEDOT was vapor phase polymerized on EDOT grafted substrates and doped with 98 % sulfuric acid. Photostability was tested using a xenon arc light source and characterized by attenuated total reflection Fourier-transform infrared spectroscopy, showing that photo-induced degradation is associated with a decrease in C[dbnd]C double bond content.