Department of Chemistry University of Copenhagen, Universitetsparken 5, 2100 Copenhagen  Inks for transparent flexible electronics have attracted increased attention due to their use in scalable manufacturing processes such as roll-to-roll production. Inks today relies mainly on transparent conductive polymers, metal oxides and metal nanoparticles. Although offering the needed conductivities for usage in e.g. touch displays, these materials suffer various drawbacks including poor stability, brittleness, high material costs or scarcity of material. These limitations demands for new replacement materials.We address this challenge by proposing a water based graphene oxide (GO) ink, which is scalable and simultaneously has low production costs due to the abundance of graphite. Most reported work on GO uses the modified Hummers' method of preparation. However, in recent years it has become clear that this method over-oxidizes the carbon framework leading to irreversible defects such as nano-sized holes and structural disorder. Mild low temperature GO synthesis as reported by Eigler et al. should therefore be the preferred starting point of GO synthesis[1]. We demonstrate screen-printing of the GO ink with subsequent and efficient TFA/HI reduction to yield semi-transparent rGO electrodes on flexible PET substrates with 327 Ohm/square at 37 % transmittance. [1] S. Eigler, M. Enzelberger-Heim, S. Grimm, P. Hofmann, W. Kroener, A. Geworski, C. Dotzer, M. Rockert, J. Xiao, C. Papp, O. Lytken, H. P. Steinruck, P. Muller and A. Hirsch, Advanced Materials, 2013, 25, 3583-3587.  Marc Overgaard is a Ph.D student at the University of Copenhagen with Bo Wegge Laursen as principal supervisor. He received his M.Sc. degree from the University of Copenhagen in 2013, where he studied porous graphene cathodes for lithium-oxygen batteries in close collaboration with the Technical University of Denmark. His Ph.D takes part of a joint Danish research initiative termed the National Initiative for Advanced Graphene Coatings and Composites (NIAGRA). His research interests are primarily focused on the synthesis and fundamental understanding of chemically derived graphene such as GO. In his work he seeks to combine the fundamentals of academia with more end-user based applications such as graphene printed electronics and surface protective graphene composite coatings. |
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