Discipline: Technology and Engineering
Subcategory: Electrical Engineering
Session: 3
Yonatal Garcia - Garden City Community College
Co-Author(s): Suprem R. Das, Kansas State University, Manhattan, KS, 66506
Graphene based Transparent and Flexible Conducting Electrodes Yonatal Garcia, Garden City Community College, Garden City, KS 67846 Co-author: Suprem R. Das, Kansas State University, Manhattan, KS 66506 Transparent conducting electrodes (TCEs) are the key components in much of today’s technologies, such as solar cells and photodetectors.1 However, due to less abundancy and more expensiveness of indium as well as the reliability issues, the decade long candidate indium tin oxide (ITO) is currently facing a serious replacement proposal with an alternate candidate with comparable or better figure of merits (FOMs). Typically, a sheet resistance of 50 ohm/square or lower and an optical transmission of 90% or higher at a wavelength of 550 nanometers are considered as acceptable FOMs. Graphene, a single atomic thick sheet of carbon atoms arranged with hexagonal bonding (sp2 carbon-carbon hybridization), has made a great success in proposal for number of technologies due to its high electrical conductivity and high optical transparency.2,3 However, scientific and technological (manufacturing) challenges still persist to develop graphene based transparent conductors reliably and cost effectively. Two methods of producing large scale graphene are the chemical vapor deposition (CVD) and solution processing of a graphene dispersion.4,5 While the former one is expensive and whole substrate method on specific metal catalysts (such as copper), later one is cheaper and user-flexible to manufacture. The outstanding issue in the solution-process technique of creating graphene TCE is making a uniform sheet of nano-platelets that achieves the recommended FOMs. In this project, we synthesize graphene dispersion and follow a drop casting and a series of processing protocols to manipulate the distribution of graphene flakes upon a ~ 0.25 cm2 substrate. In this work, we examine the optimum graphene flakes to manipulate the TCE structure and function. We use the hypothesis of inter-flake and intra-flake resistances and following our experimental results we understand the effects of sheet resistance and optical transmittance on the graphene TCE. Both rigid substrate (such as quartz) and mechanically flexible substrate (such as plastic or PET) are used to design such TCEs and their mechanical integrity is studied. Using different concentrations of graphene platelets, the results will be correlated to the physical structures of the TCE. Thermal annealing with argon (inert gas ambient) is used to ‘electronically’ clean and ‘mechanically’ join the graphene platelets to form the TCEs. Various characterizations, such as Raman spectroscopy, atomic force microscopy, and scanning electron microscopy are used to probe the graphene structure. These integrated approach, with further exploration of solution processed graphene electrodes, will allow for a tangible understanding and development of graphene based transparent conducting electrodes. References: [1] K. Ellmer, Nature Photonics 6, 809–817 (2012). [2] A. K. Geim & K.S. Novoselov, Nature Materials 6, 183–191 (2007). [3] R. R. Nair, P. Blake, A. N. Grigorenko, K. S. Novoselov, T. J. Booth, T. Stauber, N. M. R. Peres, A. K. Geim, Science 320, 1308 (2008). [4] A. Reina, X. Jia, J. Ho, D. Nezich, H. Son, V. Bulovic, M.S. Dresselhaus & J. Kong Nano Lett. 9, 30–35 (2009). [5] D. Li, M. B. Müller, S. Gilje, R. B. Kaner & G. G. Wallace, Nature Nanotechnology 3, 101–105 (2008) Funder Acknowledgement(s): I thank Industrial and Manufacturing Systems Engineering (IMSE) at College of Engineering, Kansas State University for the research support. I also thank WenJun Xiang, Levi Tucker, Pedram and Pedram Parandoush of IMSE for their help. Funding was provided by KS-LSAMP supported by National Science Foundation (or NSF) under grant number 1305059. Faculty Advisor/Mentor: Suprem R. Das, srdas@ksu.edu
Funder Acknowledgement(s): College of Engineering, Kansas State University For research funding ; Funding by KS-LSAMP, supported by National Science Foundation (or NSF) under grant number 1305059
Faculty Advisor: Suprem R. Das, srdas@ksu.edu
Role: Set up substrates to be cleaned from any impurities for the surfaces. Using a drop-casting method with a series of different dilutions. I then labeled each sample based on their different dilutions. Then I annealed the samples to unlock the graphene's conductive capability. Once this was done, I used a Optical Microscope Image to gather images of the annealed graphene flakes. Then using a Raman spectroscopy and atomic force microscopy to gather data of the samples and categorized them based on their level of dilutions. Gathering the data and showcasing in a way that shows the data on a graph. Then using a Atomic Force Microscopy I was able to get images of graphene flakes with its dimensions at a nano scale level. Then collected data on the resistance and transparency of the conductors