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LL2.02 - Inkjet Printing Graphene-Based Transparent Conductive Films 
April 22, 2014   10:45am - 11:00am

Graphene is a strong contender material for the replacement of indium tin oxide (ITO) as the transparent conductor of choice for electronic applications due to its exceptional electrical and optical properties [1]. For practical manufacturing applications, large scale production of graphene materials is necessary. To produce large quantities of graphene materials, reduction of exfoliated graphene oxide sheets is favoured because it is a solution phase method with potential low cost. The resulting graphene oxide suspensions can be processed as graphene inks and deposited to form graphene films via large scale and low cost solution process such as inkjet-printing. In this work, we present a study of conductive reduced graphene oxide films produced by inkjet-printing. Highly stable graphene ink (up to 6 months) was prepared by dispersing graphene oxide in water with a stabilizing surfactant at pH ≈ 10 by adding ammonia. This was subsequently reduced in solution-phase using hydrazine monohydrate. Printed film electrical and optical properties are shown to be strongly dependent on the mean flake size used in the ink. By using large area size of graphene oxide sheets and adjusting the number of printing layers films with electrical sheet resistance of 6 kΩ/sq and optical transparency of 65% could be achieved. These properties corresponded to a ratio between the DC (σDC) and optical (σOp) conductivities (σDC/σOp) of 0.13, which was comparable with solution processed pristine-graphene films that have been reported previously [2]. This indicates that the flake size of the ink is at least of equal importance as the quality of the graphene in determining printed transparent film properties.[1] S.-K. Bae, H.-K. Kim, Y.B. Lee, et al: “Roll-to-Roll Production of 30-inch Graphene Films for Transparent Electrodes”, Nature Nanotechnology, 5 (8), 574-578 (2010).[2] S. De, P.J. King, M. Lotya, et al: “Flexible, Transparent, Conducting Films of Randomly Stacked Graphene from Surfactant-Stabilized, Oxide-Free Graphene Dispersions”, Small, 6 (3), 458-464 (2010).

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Keynote Address
Panel Discussion - Different Approaches to Commercializing Materials Research
Business Challenges to Starting a Materials-Based Company
Fred Kavli Distinguished Lectureship in Nanoscience
Application of In-situ X-ray Absorption, Emission and Powder Diffraction Studies in Nanomaterials Research - From the Design of an In-situ Experiment to Data Analysis