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      • Theses - Department of Physics
      • Dept. of Physics - Ph.D. / Sc.D.
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      Graphene based optoelectronics in the visible spectrum

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      Embargo Lift Date: 2017-01-15
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      Author(s)
      Polat, Emre Ozan
      Advisor
      Kocabaş, Coşkun
      Date
      2015
      Publisher
      Bilkent University
      Language
      English
      Type
      Thesis
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      Abstract
      Graphene, a two dimensional crystal of carbon atoms, emerges as a viable material for optoelectronics because of its electrically-tunable broadband optical properties. Optical response of graphene at visible and near infrared frequencies is defined by inter-band electronic transitions. By electrical tuning of the Fermi energy, the inter-band transitions can be blocked due to Pauli blocking. However, controlling inter-band transitions of graphene in the visible and near infrared wavelengths, has been an outstanding challenge. We developed a new device to control optical properties of graphene in the visible spectra. Our device relies on a graphene supercapacitor which includes two parallel graphene electrodes and electrolyte between them. Mutual gating between graphene electrodes enables us to fabricate optical modulators which can operate in the visible and near-infrared. Single layer graphene, however, has performance limits due to its small optical absorption defined by fundamental constants. We extend our method and we developed a new class of electrochromic devices using multilayer graphene. Fabricated devices undergo a reversible color change with the electrically controlled intercalation process. The electrical and optical characterizations of the electrochromic devices reveal the broadband optical modulation up to 55 per cent in the visible and near-infrared. Integration of semiconducting materials on unconventional substrates enables optoelectronic devices with new mechanical functionalities that cannot be achieved with wafer-based technologies. As a novel application, we demonstrate ultra thin electronic paper displays using the multilayer graphene as a reconfigurable optical medium. We anticipate that the developed devices would find wide range of applications in optoelectronics.
      Keywords
      Graphene
      Optical modulator
      Optoelectronics
      Supercapacitor
      Smart window
      Electrochromic devices
      Electrolyte
      Permalink
      http://hdl.handle.net/11693/18504
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      • Dept. of Physics - Ph.D. / Sc.D. 74
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