Versatile and Tunable Transparent Conducting Electrodes Based on Doped Graphene

Handle URI:
http://hdl.handle.net/10754/621935
Title:
Versatile and Tunable Transparent Conducting Electrodes Based on Doped Graphene
Authors:
Mansour, Ahmed E. ( 0000-0002-3411-6808 )
Abstract:
The continued growth of the optoelectronics industry and the emergence of wearable and flexible electronics will continue to place an ever increasing pressure on replacing ITO, the most widely used transparent conducting electrode (TCE). Among the various candidates, graphene shows the highest optical transmittance in addition to promising electrical transport properties. The currently available large-scale synthesis routes of graphene result in polycrystalline samples rife with grain boundaries and other defects which limit its transport properties. Chemical doping of graphene is a viable route towards increasing its conductivity and tuning its work function. However, dopants are typically present at the surface of the graphene sheet, making them highly susceptible to degradation in environmental conditions. Few-layers graphene (FLG) is a more resilient form of graphene exhibiting higher conductivity and performance stability under stretching and bending as contrasted to single-layer graphene. In addition FLG presents the advantage of being amenable bulk doping by intercalation. Herein, we explore non-covalent doping routes of CVD FLG, such as surface doping, intercalation and combination thereof, through in-depth and systematic characterization of the electrical transport properties and energy levels shifts. The intercalation of FLG with Br2 and FeCl3 is demonstrated, showing the highest improvements of the figure of merit of TCEs of any doping scheme, which results from up to a five-fold increase in conductivity while maintaining the transmittance within 3% of that for the pristine value. Importantly the intercalation yields TCEs that are air-stable, due to encapsulation of the intercalant in the bulk of FLG. Surface doping with novel solution-processed metal-organic molecular species (n- and p-type) is demonstrated with an unprecedented range of work function modulation, resulting from electron transfer and the formation of molecular surface dipoles. However, the conductivity increases compared modestly to intercalation as the electron transfer is limited to the uppermost graphene layers. Finally, a novel and universal multi-modal doping strategy is developed, thanks to the unique platform offered by FLG, where surface and intercalation doping are combined to mutually achieve high conductivity with an extended tunability of the work function. This work presents doped-FLG as a prospective and versatile candidate among emerging TCEs, given the need for efficient and stable doping routes capable of controllably tuning its properties to meet the criteria of a broad range of applications.
Advisors:
Amassian, Aram ( 0000-0002-5734-1194 )
Committee Member:
Alshareef, Husam N. ( 0000-0001-5029-2142 ) ; McCulloch, Iain ( 0000-0002-6340-7217 ) ; Samori, Paolo
KAUST Department:
Physical Sciences and Engineering (PSE) Division
Program:
Materials Science and Engineering
Issue Date:
25-Nov-2016
Type:
Dissertation
Appears in Collections:
Dissertations

Full metadata record

DC FieldValue Language
dc.contributor.advisorAmassian, Aramen
dc.contributor.authorMansour, Ahmed E.en
dc.date.accessioned2016-12-05T06:31:18Z-
dc.date.available2016-12-05T06:31:18Z-
dc.date.issued2016-11-25-
dc.identifier.urihttp://hdl.handle.net/10754/621935-
dc.description.abstractThe continued growth of the optoelectronics industry and the emergence of wearable and flexible electronics will continue to place an ever increasing pressure on replacing ITO, the most widely used transparent conducting electrode (TCE). Among the various candidates, graphene shows the highest optical transmittance in addition to promising electrical transport properties. The currently available large-scale synthesis routes of graphene result in polycrystalline samples rife with grain boundaries and other defects which limit its transport properties. Chemical doping of graphene is a viable route towards increasing its conductivity and tuning its work function. However, dopants are typically present at the surface of the graphene sheet, making them highly susceptible to degradation in environmental conditions. Few-layers graphene (FLG) is a more resilient form of graphene exhibiting higher conductivity and performance stability under stretching and bending as contrasted to single-layer graphene. In addition FLG presents the advantage of being amenable bulk doping by intercalation. Herein, we explore non-covalent doping routes of CVD FLG, such as surface doping, intercalation and combination thereof, through in-depth and systematic characterization of the electrical transport properties and energy levels shifts. The intercalation of FLG with Br2 and FeCl3 is demonstrated, showing the highest improvements of the figure of merit of TCEs of any doping scheme, which results from up to a five-fold increase in conductivity while maintaining the transmittance within 3% of that for the pristine value. Importantly the intercalation yields TCEs that are air-stable, due to encapsulation of the intercalant in the bulk of FLG. Surface doping with novel solution-processed metal-organic molecular species (n- and p-type) is demonstrated with an unprecedented range of work function modulation, resulting from electron transfer and the formation of molecular surface dipoles. However, the conductivity increases compared modestly to intercalation as the electron transfer is limited to the uppermost graphene layers. Finally, a novel and universal multi-modal doping strategy is developed, thanks to the unique platform offered by FLG, where surface and intercalation doping are combined to mutually achieve high conductivity with an extended tunability of the work function. This work presents doped-FLG as a prospective and versatile candidate among emerging TCEs, given the need for efficient and stable doping routes capable of controllably tuning its properties to meet the criteria of a broad range of applications.en
dc.language.isoenen
dc.subjectDopingen
dc.subjectFew-layer grapheneen
dc.subjectIntercalationen
dc.subjectTransparent Conductive Electrodesen
dc.subjectWork functionen
dc.subjectHall effecten
dc.titleVersatile and Tunable Transparent Conducting Electrodes Based on Doped Grapheneen
dc.typeDissertationen
dc.contributor.departmentPhysical Sciences and Engineering (PSE) Divisionen
thesis.degree.grantorKing Abdullah University of Science and Technologyen_GB
dc.contributor.committeememberAlshareef, Husam N.en
dc.contributor.committeememberMcCulloch, Iainen
dc.contributor.committeememberSamori, Paoloen
thesis.degree.disciplineMaterials Science and Engineeringen
thesis.degree.nameDoctor of Philosophyen
dc.person.id101717en
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