Poly(3-hexylthiophene)-Based Organic Thin-Film Transistors with Virgin Graphene Oxide as an Interfacial Layer.

We fabricated and characterized poly(3-hexylthiophene-2, 5-diyl) (P3HT)-based Organic thin-film transistors (OTFTs) containing an interfacial layer made from virgin Graphene Oxide (GO). Previously chemically modified GO and reduced GO (RGO) were used to modify OTFT interfaces. However, to our knowledge, there are no published reports where virgin GO was employed for this purpose. For the sake of comparison, OTFTs without modification were also manufactured. The structure of the devices was based on the Bottom Gate Bottom Contact (BGBC) OTFT. We show that the presence of the GO monolayer on the surface of the OTFT's SiO2 dielectric and Au electrode surface noticeably improves their performance. Namely, the drain current and the field-effect mobility of OTFTs are considerably increased by modifying the interfaces with the virgin GO deposition. It is suggested that the observed enhancement is connected to a decrease in the contact resistance of GO-covered Au electrodes and the particular structure of the P3HT layer on the dielectric surface. Namely, we found a specific morphology of the organic semiconductor P3HT layer, where larger interconnecting polymer grains are formed on the surface of the GO-modified SiO2. It is proposed that this specific morphology is formed due to the increased mobility of the P3HT segments near the solid boundary, which was confirmed via Differential Scanning Calorimetry measurements.

Highly Conductive and Transparent Reduced Graphene Oxide Nanoscale Films via Thermal Conversion of Polymer-Encapsulated Graphene Oxide Sheets.

Despite noteworthy progress in the fabrication of large-area graphene sheetlike nanomaterials, the vapor-based processing still requires sophisticated equipment and a multistage handling of the material. An alternative approach to manufacturing functional graphene-based films includes the employment of graphene oxide (GO) micrometer-scale sheets as precursors. However, search for a scalable manufacturing technique for the production of high-quality GO nanoscale films with high uniformity and high electrical conductivity is still continuing. Here we show that conventional dip-coating technique can offer fabrication of high quality mono- and bilayered films made of GO sheets. The method is based on our recent discovery that encapsulating individual GO sheets in a nanometer thick molecular brush copolymer layer allows for the nearly perfect formation of the GO layers via dip coating from water. By thermal reduction the bilayers (cemented by a carbon-forming polymer linker) are converted into highly conductive and transparent reduced GO films with a high conductivity up to 104 S/cm and optical transparency on the level of 90%. The value is the highest electrical conductivity reported for thermally reduced nanoscale GO films and is close to the conductivity of indium tin oxide currently in use for transparent electronic devices, thus making these layers intriguing candidates for replacement of ITO films.