Graphene−Silica Composite Thin Films as Transparent Conductors

Watcharotone, Supinda; Dikin, Dmitriy A.; Stankovich, Sasha; Piner, Richard D.; Jung, Inhwa; Dommett, Geoffrey; Evmenenko, Guennadi; Wu, Shang-En; Chen, Shu-Fang; Liu, Chuan‐Pu; Nguyen, SonBinh T.; Ruoff, Rodney S.

doi:10.1021/nl070477+

Cited by 840 publications

(600 citation statements)

References 49 publications

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“…This sheet resistance is nearly 2 orders of magnitude lower than the analogous vapor reduced GO films reported previously (∼1 MΩ/0 and 80-85% transmittance). [13][14][15][16][17][18] To explain the vast improvement in sheet resistance of a G-CNT electrode, we suggest the formation of an extended conjugated network with individual CNTs bridging the gaps between graphene sheets. The large graphene sheets cover the majority of the total surface area, while the CNTs act as wires connecting the large pads together.…”

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confidence: 94%

“…The challenge has been in scaling up the mechanical cleavage of graphite. 14 Singlelayer samples are most often the result of a laborious peeling method, which is neither scalable nor capable of producing uniform depositions. Recently, researchers have circumvented the problem of mechanical cleavage by using graphite oxide (GO), a layered compound that can be readily dispersed as individual sheets in a good solvent.…”

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confidence: 99%

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Low-Temperature Solution Processing of Graphene−Carbon Nanotube Hybrid Materials for High-Performance Transparent Conductors

et al. 2009

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We report the formation of a nanocomposite comprised of chemically converted graphene and carbon nanotubes. Our solution-based method does not require surfactants, thus preserving the intrinsic electronic and mechanical properties of both components, delivering 240 Ω/0 at 86% transmittance. This low-temperature process is completely compatible with flexible substrates and does not require a sophisticated transfer process. We believe that this technology is inexpensive, is massively scalable, and does not suffer from several shortcomings of indium tin oxide. A proof-of-concept application in a polymer solar cell with power conversion efficiency of 0.85% is demonstrated. Preliminary experiments in chemical doping are presented and show that optimization of this material is not limited to improvements in layer morphology.

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confidence: 94%

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confidence: 99%

Low-Temperature Solution Processing of Graphene−Carbon Nanotube Hybrid Materials for High-Performance Transparent Conductors

et al. 2009

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“…[2][3][4][5][6][7] However, just as with other newly discovered allotropes of carbon (fullerenes and single-wall nanotubes), material availability and processability will be the ratelimiting steps in the evaluation of putative applications of graphene. For graphene, that availability is encumbered by having to surmount the high cohesive van der Waals energy (5.9 kJ mol -1 carbon) 8 adhering graphitic sheets to one another.…”

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confidence: 99%

“…With further surface modifications, graphene that is soluble in organic solvents should be accessible thereby further expediting the application of graphene in composite materials, emissive displays, micromechanical resonators, transistors, and ultrasensitive chemical detectors. [2][3][4][5][6][7] …”

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confidence: 99%

Synthesis of Water Soluble Graphene

2008

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A facile and scalable preparation of aqueous solutions of isolated, sparingly sulfonated graphene is reported. 13 C NMR and FTIR spectra indicate that the bulk of the oxygen-containing functional groups was removed from graphene oxide. The electrical conductivity of thin evaporated films of graphene (1250 S/m) relative to similarly prepared graphite (6120 S/m) implies that an extended conjugated sp 2 network is restored in the water soluble graphene.Recently characterized as "the thinnest material in our universe", 1 graphene, a single-atom-thick sheet of hexagonally arrayed sp 2 -bonded carbon atoms, promises a diverse range of applications from composite materials to quantum dots. [2][3][4][5][6][7] However, just as with other newly discovered allotropes of carbon (fullerenes and single-wall nanotubes), material availability and processability will be the ratelimiting steps in the evaluation of putative applications of graphene. For graphene, that availability is encumbered by having to surmount the high cohesive van der Waals energy (5.9 kJ mol -1 carbon) 8 adhering graphitic sheets to one another. Herein, we describe a facile and scalable preparation of aqueous solutions of isolated, sparingly sulfonated graphene sheets starting from oxidized graphite. The measured electrical conductivity of contiguous films of graphene prepared by evaporation of an aqueous solution implies that the extensive conjugated sp 2 carbon network is restored in the water soluble graphene.Graphene was initially isolated by mechanical exfoliation, peeling off the top surface of small mesas of pyrolytic graphite, 2,5 a method which is not suitable for large-scale application. More recently, single sheets of graphene oxide were chemically reduced to graphene after deposition on a silicon substrate, 9,10 again a method that lends itself to limited applications. Exfoliation of graphite oxidized with strong acids either by rapid thermal expansion 11 or by ultrasonic dispersion 12,13 is one approach to obtain (functionalized) graphene oxide in bulk. The oxidation chemistry is similar to that used to functionalize single-wall carbon nanotubes (SWNTs) [14][15][16] and yields a variety of oxygen functionalities (sOH, sOs, and sCOOH) primarily at "defect" sites on SWNT ends. For sufficiently strong oxidizing agents, functionalized defects were also created on the SWNT wall surfaces. 17 Therefore, independent of the exfoliation mechanics, graphene oxide prepared from oxidized graphite includes significant oxygen functionality 11 and defects so the associated structural and electronic perturbations caused by oxidation must be repaired to recover the unique properties of graphene. These perturbations can be superficially ameliorated with "passivation chemistry," for example, reacting graphene oxide with amines, 12 but the resulting materials are not expected to exhibit the electronic attributes of graphene because of residual (passivated) defects.Ideally graphene oxide must be rigorously reduced after exfoliation to recover the desirable ...

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“…1 Graphene, a single sheet of graphite, possesses extraordinary electrical, thermal, and mechanical properties arising from its unique structure. 2 When incorporated into polymer [3][4][5][6] or ceramic 7 matrices, these properties manifest as remarkable improvements in the host material. Graphene-based polymer composites exhibit extraordinarily low electrical percolation threshold (0.1 vol %) due to large conductivity and aspect ratio of the graphene sheets (atomic thickness and micrometersized lateral dimensions).…”

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confidence: 99%

Graphene-based Composite Thin Films for Electronics

2009

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The electrical properties of solution-processed composite thin films consisting of functionalized graphene sheets (FGS) as the filler and polystyrene (PS) as the host material are described. We demonstrate that transistors from graphene-based composite thin films exhibit ambipolar field effect characteristics, suggesting transport via percolation among FGS in the insulating PS matrix. Device characteristics as a function of the FGS size are also reported. The results indicate that devices fabricated using the largest size FGS yield the highest mobility values. This simple and scaleable fabrication scheme based on a commodity plastic could be useful for low-cost, macro-scale electronics.Graphene-based composites are emerging as new class of materials that hold promise for several applications. 1 Graphene, a single sheet of graphite, possesses extraordinary electrical, thermal, and mechanical properties arising from its unique structure. 2 When incorporated into polymer 3-6 or ceramic 7 matrices, these properties manifest as remarkable improvements in the host material. Graphene-based polymer composites exhibit extraordinarily low electrical percolation threshold (0.1 vol %) due to large conductivity and aspect ratio of the graphene sheets (atomic thickness and micrometersized lateral dimensions). 3,6 The mechanical and thermal properties of these materials rank among the best in comparison with other carbon-based composites due to strong interactions between polymer hosts and graphene sheets. 1,5 The highly conductive nature of graphene and ease of incorporation into polymers and ceramics has also opened up the possibility of their use as transparent conductors. 7 Furthermore, we recently demonstrated that atomically sharp edges of graphene incorporated into a PS host can be exploited for field emission. 8 Graphene is a zero band gap semiconductor exhibiting large electric field effect, 9 allowing doping with electrons or holes via electrostatic gating. The fact that graphene does not have a band gap poses a challenge for digital applications, but its high mobility is attractive for high frequency analog electronics or spintronics. 10,11 The semiconducting and robust mechanical properties of reduced graphene have been exploited for macro-scale thin film electronic devices 12,13 and high performance resonators. 14 Semiconducting behavior has yet to be demonstrated in graphene-based composites. The compatibility of graphene with polymers and ceramics opens up a route toward realization of semiconducting composite materials from electrically passive host materials. That is, introduction of percolating graphene network within an insulating material may render it semiconducting. In this study, we show that incorporation of functionalized graphene sheets (FGS) in polystyrene (PS) matrix results in composite thin films that are semiconducting and exhibit ambipolar field effect. These composites can be deposited uniformly over large areas in the form of thin films from solution onto which devices can be fabricate...

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Graphene−Silica Composite Thin Films as Transparent Conductors

Cited by 840 publications

References 49 publications

Low-Temperature Solution Processing of Graphene−Carbon Nanotube Hybrid Materials for High-Performance Transparent Conductors

Low-Temperature Solution Processing of Graphene−Carbon Nanotube Hybrid Materials for High-Performance Transparent Conductors

Synthesis of Water Soluble Graphene

Graphene-based Composite Thin Films for Electronics

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