| 1. |
- Del, Sepideh Khandan, et al.
(författare)
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Optimizing the optical and electrical properties of graphene ink thin films by laser-annealing
- 2015
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Ingår i: Current Opinion in Chemical Engineering. - : Institute of Physics (IOP). - 2211-3398. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate a facile fabrication technique for graphene-based transparent conductive films. Highly flat and uniform graphene films are obtained through the incorporation of an efficient laser annealing technique with one-time drop casting of high-concentration graphene ink. The resulting thin films are uniform and exhibit a transparency of more than 85% at 550 nm and a sheet resistance of about 30 kΩ/sq. These values constitute an increase of 45% in transparency, a reduction of surface roughness by a factor of four and a decrease of 70% in sheet resistance compared to un-annealed films.
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| 2. |
- Delekta, Szymon Sollami, et al.
(författare)
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Fully inkjet printed ultrathin microsupercapacitors based on graphene electrodes and a nano-graphene oxide electrolyte
- 2019
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 11:21, s. 10172-10177
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Tidskriftsartikel (refereegranskat)abstract
- The advance of miniaturized and low-power electronics has a striking impact on the development of energy storage devices with constantly tougher constraints in terms of form factor and performance. Microsupercapacitors (MSCs) are considered a potential solution to this problem, thanks to their compact device structure. Great efforts have been made to maximize their performance with new materials like graphene and to minimize their production cost with scalable fabrication processes. In this regard, we developed a full inkjet printing process for the production of all-graphene microsupercapacitors with electrodes based on electrochemically exfoliated graphene and an ultrathin solid-state electrolyte based on nano-graphene oxide. The devices exploit the high ionic conductivity of nano-graphene oxide coupled with the high electrical conductivity of graphene films, yielding areal capacitances of up to 313 mu F cm-2 at 5 mV s-1 and high power densities of up to 4 mW cm-3 with an overall device thickness of only 1 mu m.
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| 3. |
- Delekta, Szymon Sollami, et al.
(författare)
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Inkjet printed highly transparent and flexible graphene micro-supercapacitors
- 2017
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 9:21, s. 6998-7005
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Tidskriftsartikel (refereegranskat)abstract
- Modern energy storage devices for portable and wearable technologies must fulfill a number of requirements, such as small size, flexibility, thinness, reliability, transparency, manufacturing simplicity and performance, in order to be competitive in an ever expanding market. To this end, a comprehensive inkjet printing process is developed for the scalable and low-cost fabrication of transparent and flexible micro-supercapacitors. These solid-state devices, with printed thin films of graphene flakes as interdigitated electrodes, exhibit excellent performance versus transparency (ranging from a single-electrode areal capacitance of 16 mu F cm(-2) at transmittance of 90% to a capacitance of 99 mu F cm(-2) at transmittance of 71%). Also, transparent and flexible devices are fabricated, showing negligible capacitance degradation during bending. The ease of manufacturing coupled with their great capacitive properties opens up new potential applications for energy storage devices ranging from portable solar cells to wearable sensors.
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| 4. |
- Delekta, Szymon Sollami, et al.
(författare)
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Wet Transfer of Inkjet Printed Graphene for Microsupercapacitors on Arbitrary Substrates
- 2019
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Ingår i: ACS Applied Energy Materials. - : American Chemical Society (ACS). - 2574-0962. ; 2:1, s. 158-163
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Tidskriftsartikel (refereegranskat)abstract
- Significant research interest is being devoted to exploiting the properties of graphene but the difficult integration on various substrates limits its use. In this regard, we developed a transfer technique that allows the direct deposition of inkjet printed graphene devices on arbitrary substrates, even 3D objects and living plants. With this technique, we fabricated micro-supercapacitors, which exhibited good adhesion on almost all substrates and no performance degradation induced by the process. Specifically, the microsupercapacitor on an orchid leaf showed an areal capacitance as high as 441 mu F cm(-2) and a volumetric capacitance of 1.16 F cm(-3). This technique can boost the use of graphene in key technological applications, such as self powered epidermal electronics and environmental monitoring systems.
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| 5. |
- Li, Jiantong, et al.
(författare)
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All-solid-state micro-supercapacitors based on inkjet printed graphene electrodes
- 2016
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 109:12
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Tidskriftsartikel (refereegranskat)abstract
- The all-solid-state graphene-based in-plane micro-supercapacitors are fabricated simply through reliable inkjet printing of pristine graphene in interdigitated structure on silicon wafers to serve as both electrodes and current collectors, and a following drop casting of polymer electrolytes (polyvinyl alcohol/H3PO4). Benefiting from the printing processing, an attractive porous electrode microstructure with a large number of vertically orientated graphene flakes is observed. The devices exhibit commendable areal capacitance over 0.1 mF/cm(2) and a long cycle life of over 1000 times. The simple and scalable fabrication technique for efficient micro-supercapacitors is promising for on-chip energy storage applications in emerging electronics.
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| 6. |
- Li, Jiantong, et al.
(författare)
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Conductivity scaling in supercritical percolation of nanoparticles : not a power law
- 2015
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Ingår i: Nanoscale. - : Royal Society of Chemistry. - 2040-3364 .- 2040-3372. ; 7:8, s. 3424-3428
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Tidskriftsartikel (refereegranskat)abstract
- The power-law behavior widely observed in supercritical percolation systems of conductive nanoparticles may merely be a phenomenological approximation to the true scaling law not yet discovered. In this work, we derive a comprehensive yet simple scaling law and verify its extensive applicability to various experimental and numerical systems. In contrast to the power law which lacks theoretical backing, the new scaling law is explanatory and predictive, and thereby helpful to gain more new insights into percolation systems of conductive nanoparticles.
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| 7. |
- Li, Jiantong, et al.
(författare)
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Precise percolation thresholds of two-dimensional random systems comprising overlapping ellipses
- 2016
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Ingår i: Physica A. - : Elsevier. - 0378-4371 .- 1873-2119. ; 462, s. 940-950
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Tidskriftsartikel (refereegranskat)abstract
- This work explores the percolation thresholds of continuum systems consisting of randomly-oriented overlapping ellipses. High-precision percolation thresholds for various homogeneous ellipse systems with different aspect ratios are obtained from extensive Monte Carlo simulations based on the incorporation of Vieillard-Baron's contact function of two identical ellipses with our efficient algorithm for continuum percolation. In addition, we generalize Vieillard-Baron's contact function from identical ellipses to unequal ellipses, and extend the Monte Carlo algorithm to heterogeneous ellipse systems where the ellipses have different dimensions and/or aspect ratios. Based on the concept of modified excluded area, a general law is verified for precise prediction of percolation threshold for many heterogeneous ellipse systems. In particular, the study of heterogeneous ellipse systems gains insight into the apparent percolation threshold symmetry observed earlier in systems comprising unequal circles (Consiglio et al., 2004).
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| 8. |
- Li, Jiantong, 1980-, et al.
(författare)
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Scalable Fabrication and Integration of Graphene Microsupercapacitors through Full Inkjet Printing
- 2017
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Ingår i: ACS Nano. - : American Chemical Society (ACS). - 1936-0851 .- 1936-086X. ; 11:8, s. 8249-8256
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Tidskriftsartikel (refereegranskat)abstract
- A simple full-inkjet-printing technique is developed for the scalable fabrication of graphene-based microsupercapacitors (MSCs) on various substrates. High-performance graphene inks are formulated by integrating the electrochemically exfoliated graphene with a solvent exchange technique to reliably print graphene interdigitated electrodes with tunable geometry and "thickness. Along with the printed polyelectrolyte, poly(4-styrenesulfonic acid), the fully printed graphene-based MSCs attain the highest areal capacitance of similar to 0.7 mF/cm(2), substantially advancing the state-of-art of all-solid-state MSCs with printed graphene electrodes. The full printing solution enables scalable fabrication of MSCs and effective connection of them in parallel and/or in series at various scales. Remarkably, more than 100 devices have been connected to form large-scale MSC arrays as power banks on both silicon wafers and Kapton. Without any extra protection or encapsulation, the MSC arrays can be reliably charged up to 12 V and retain the performance even 8 months after fabrication.
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| 9. |
- Li, Jiantong, et al.
(författare)
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Scalable Fabrication of 2D Semiconducting Crystals for Future Electronics
- 2015
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Ingår i: Electronics. - : MDPI. - 2079-9292. ; 4:4, s. 1033-1061
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Forskningsöversikt (refereegranskat)abstract
- Two-dimensional (2D) layered materials are anticipated to be promising for future electronics. However, their electronic applications are severely restricted by the availability of such materials with high quality and at a large scale. In this review, we introduce systematically versatile scalable synthesis techniques in the literature for high-crystallinity large-area 2D semiconducting materials, especially transition metal dichalcogenides, and 2D material-based advanced structures, such as 2D alloys, 2D heterostructures and 2D material devices engineered at the wafer scale. Systematic comparison among different techniques is conducted with respect to device performance. The present status and the perspective for future electronics are discussed.
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| 10. |
- Lobov, Gleb, et al.
(författare)
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Dynamic manipulation of optical anisotropy of suspended Poly-3-hexylthiophene nanofibers
- 2016
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Ingår i: Advanced Optical Materials. - : Wiley. - 2162-7568 .- 2195-1071. ; 4:10, s. 1651-1656
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Tidskriftsartikel (refereegranskat)abstract
- Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline semiconducting nanostructures, which are known for their application in photovoltaics. Due to the internal arrangement, P3HT nanofibers possess optical anisotropy, which can be enhanced on a macroscale if nanofibers are aligned. Alternating electric field, applied to a solution with dispersed nanofibers, causes their alignment and serves as a method to produce solid layers with ordered nanofibers. The transmission ellipsometry measurements demonstrate the dichroic absorption and birefringence of ordered nanofibers in a wide spectral range of 400–1700 nm. Moreover, the length of nanofibers has a crucial impact on their degree of alignment. Using electric birefringence technique, it is shown that external electric field applied to the solution with P3HT nanofibers can cause direct birefringence modulation. Dynamic alignment of dispersed nanofibers changes the refractive index of the solution and, therefore, the polarization of transmitted light. A reversible reorientation of nanofibers is organized by using a quadrupole configuration of poling electrodes. With further development, the described method can be used in the area of active optical fiber components, lab-on-chip or sensors. It also reveals the potential of 1D conducting polymeric structures as objects whose highly anisotropic properties can be implemented in electro-optical applications..
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| 11. |
- Lobov, Gleb, et al.
(författare)
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Optical birefringence from P3HT nanofibers in alternating electric field
- 2016
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Ingår i: Optics InfoBase Conference Papers. - : OSA - The Optical Society. - 9781943580194
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Konferensbidrag (refereegranskat)abstract
- AC poling allowing to control the orientation of P3HT nanofibers, result in strong optical birefringence with promising implementation in a novel type of optical modulator, without necessary embedding into any hosting matrix, e.g. liquid crystal.
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| 12. |
- Lobov, Gleb S., et al.
(författare)
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Electric field induced optical anisotropy of P3HT nanofibers in a liquid solution
- 2015
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Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 5:11, s. 2642-2647
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Tidskriftsartikel (refereegranskat)abstract
- The nanofiber morphology of regioregular Poly-3- hexylthiophene (P3HT) is a 1D crystalline structure organized by π - π stacking of the backbone chains. In this study, we report the impact of electric field on the orientation and optical properties of P3HT nanofibers dispersed in liquid solution. We demonstrate that alternating electric field aligns nanofibers, whereas static electric field forces them to migrate towards the cathode. The alignment of nanofibers introduces anisotropic optical properties, which can be dynamically manipulated until the solvent has evaporated. Time resolved spectroscopic measurements revealed that the electro-optical response time decreases significantly with the magnitude of applied electric field. Thus, for electric field 1.3 V ·μm-1 the response time was measured as low as 20 ms, while for 0.65 V ·μm-1 it was 110-150 ms. Observed phenomenon is the first mention of P3HT supramolecules associated with electrooptical effect. Proposed method provides real time control over the orientation of nanofibers, which is a starting point for a novel practical implementation. With further development P3HT nanofibers can be used individually as an anisotropic solution or as an active component in a guest-host system.
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| 13. |
- Lobov, Gleb S., et al.
(författare)
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Electro-optical response of P3HT nanofibers in liquid solution
- 2015
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Ingår i: Asia Communications and Photonics Conference, ACPC 2015. - Washington, D.C. : OSA. - 9781943580064
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Konferensbidrag (refereegranskat)abstract
- AC electric poling introduces in P3HT nanofibers anisotropic electro-optical response and birefringence. Along with birefringence, such material exhibits strong amplitude modulation which makes it more efficient alternative to liquid crystals.
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| 14. |
- Lobov, Gleb S., et al.
(författare)
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Electro-optical response of P3HT nanofibers in liquid solution
- 2015
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Ingår i: Asia Communications and Photonics Conference 2015. - : Optical Society of America. - 9781943580064
-
Konferensbidrag (refereegranskat)abstract
- AC electric poling introduces in P3HT nanofibers anisotropic electro-optical response and birefringence. Along with birefringence, such material exhibits strong amplitude modulation which makes it more efficient alternative to liquid crystals.
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| 15. |
- Lobov, Gleb S., et al.
(författare)
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Size Impact of Ordered P3HT Nanofibers on Optical Anisotropy
- 2016
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Ingår i: Macromolecular Chemistry and Physics. - : John Wiley & Sons. - 1022-1352 .- 1521-3935. ; 217:9, s. 1089-1095
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Tidskriftsartikel (refereegranskat)abstract
- Poly-3-hexylthiophene (P3HT) nanofibers are 1D crystalline structures with semiconductor properties. When P3HT nanofi bers are dispersed in nonconducting solvent, they react to external alternate electric field by aligning along the field lines. This can be used to create layers of ordered nanofi bers and is referred to as alternating current poling method. P3HT nanofi bers with three different size distributions are fabricated, using self-assembly mechanism in marginal solvents, and used for the alignment studies. Anisotropic absorption of oriented 2 mu m long nanofi bers exponentially increases with the magnitude of applied field to a certain asymptotic limit at 0.8 V mu m(-1), while 100-500 nm long nanofi bers respond to electric field negligibly. Effective optical birefringence of oriented 2 mu m long nanofi bers is calculated, based on the phase shift at 633 nm and the average layer thickness, to be 0.41. These results combined with further studies on real-time control over orientation of P3HT nanofi bers in liquid solution or host system are promising in terms of exploiting them in electroabsorptive and electrorefractive applications.
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| 16. |
- Loiko, P., et al.
(författare)
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Inkjet-printing of graphene saturable absorbers for ~2 μm bulk and waveguide lasers
- 2017
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Ingår i: Optics InfoBase Conference Papers. - : Optical Society of America. - 9781943580279
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Konferensbidrag (refereegranskat)abstract
- We report on inkjet-printing of graphene saturable absorbers (SAs) suitable for passive Qswitching of ~2-μm bulk and waveguide lasers. Using graphene-SA in a microchip Tm:KLu(WO4)2 laser, 1.2 μJ/136 ns pulses are generated at 1917 nm.
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| 17. |
- Loiko, Pavel, et al.
(författare)
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Inkjet-Printing of Graphene Saturable Absorbers for similar to 2 mu m Bulk and Waveguide Lasers
- 2017
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Ingår i: 2017 CONFERENCE ON LASERS AND ELECTRO-OPTICS (CLEO). - : IEEE. - 9781943580279
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Konferensbidrag (refereegranskat)abstract
- We report on inkjet-printing of graphene saturable absorbers (SAs) suitable for passive Q-switching of similar to 2-mu m bulk and waveguide lasers. Using graphene-SA in a microchip Tm:KLu(WO4)(2) laser, 1.2 mu J/136 ns pulses are generated at 1917 nm.
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| 18. |
- Loiko, Pavel, et al.
(författare)
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Inkjet-printing of graphene saturable absorbers for similar to 2 mu m bulk and waveguide lasers
- 2018
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Ingår i: Optical Materials Express. - : Optical Society of America. - 2159-3930 .- 2159-3930. ; 8:9, s. 2803-2814
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Tidskriftsartikel (refereegranskat)abstract
- A technique for inkjet-printing of graphene saturable absorbers (SAs) for similar to 2-mu m bulk and waveguide lasers is presented. Based on distillation-assisted solvent exchange to fabricate high-concentration graphene inks, this technique is capable of producing few-layer graphene films of arbitrary shape. Absorption saturation of graphene printed on glass is demonstrated at similar to 1.56 mu m for picosecond and femtosecond pulses indicating a large fraction of the saturable losses. Inkjet-printed transmission-type graphene SAs are applied in passively Q-switched nanosecond thulium (Tm) microchip and planar waveguide lasers. The Tm microchip laser generates 136 ns / 1.2 mu J pulses at 1917 nm with a repetition rate of 0.37 MHz with a Q-switching conversion efficiency reaching 65%. The planar waveguide laser generates 98 ns / 21 nJ pulses at 1834 nm at a repetition rate in the MHz-range. The inkjet-printing technique is promising for production of patterned SAs for waveguide lasers.
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| 19. |
- Sollami Delekta, Szymon, 1990-
(författare)
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Inkjet Printing of Graphene-based Microsupercapacitors for Miniaturized Energy Storage Applications
- 2019
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Printing technologies are becoming increasingly popular because they enable the large-scale and low-cost production of functional devices with various designs, functions, mechanical properties and materials. Among these technologies, inkjet printing is promising thanks to its direct (mask-free) patterning, non-contact nature, low material waste, resolution down to 10 µm, and compatibility with a broad range of materials and substrates. As a result, inkjet printing has applications in several fields like wearables, opto-electronics, thin-film transistors, displays, photovoltaic devices, and in energy storage. It's in energy storage that the technique shows its full potential by allowing the production of miniaturized devices with a compact form factor, high power density and long cycle life, called microsupercapacitors (MSCs). To this end, graphene has a number of remarkable properties like high electrical conductivity, large surface area, elasticity and transparency, making it a top candidate as an electrode material for MSCs.Some key drawbacks limit the use of inkjet printing for the production of graphene-based MSCs. This thesis aims at improving its scalability by producing fully inkjet printed devices, and extending its applications through the integration of inkjet printing with other fabrication techniques.MSCs typically rely on the deposition by hand of gel electrolyte that is not printable or by submerging the whole structure into liquid electrolyte. Because of this, so far large-scale production of more than 10 interconnected devices has not been attempted. In this thesis, a printable gel electrolyte ink based on poly(4-styrene sulfonic acid) was developed, allowing the production of large arrays of more than 100 fully inkjet printed devices connected in series and parallel that can be reliably charged up to 12 V. Also, a second electrolyte ink based on nano-graphene oxide, a solid-state material with high ionic conductivity, was formulated to optimize the volumetric performance of these devices. The resulting MSCs were also fully inkjet printed and exhibited an overall device thickness of around 1 µm, yielding a power density of 80 mW cm-3.Next, the use of inkjet printing of graphene was explored for the fabrication of transparent MSCs. This application is typically hindered by the so-called coffee-ring effect, which creates dark deposits on the edges of the drying patterns and depletes material from the inside area. In light of this issue, inkjet printing was combined with etching to remove the dark deposits thus leaving uniform and thin films of graphene with vertical sidewalls. The resulting devices showed a transmittance of up to 90%.Finally, the issue of the substrate compatibility of inkjet printed graphene was addressed. Although inkjet printing is considered to have broad substrate versatility, it is unreliable on hydrophilic or porous substrates and most inks (including graphene inks) require thermal annealing that damages substrates that are not resistant to heat. Accordingly, a technique based on inkjet printing and wet transfer was developed to reliably deposit graphene-based MSCs on a number of substrates, including flat, 3D, porous, plastics and biological (plants and fruits) with adverse surfaces.The contributions of this thesis have the potential to boost the use of inkjet printed MSCs in applications requiring scalability and resolution (e.g. on-chip integration) as well as applications requiring conformability and versatility (e.g. wearable electronics).
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| 20. |
- Östling, Mikael, et al.
(författare)
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Emerging graphene device technologies
- 2016
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Ingår i: Emerging Nanomaterials and Devices. - : Electrochemical Society. - 9781607685395 ; , s. 17-35
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Konferensbidrag (refereegranskat)abstract
- Graphene has a wide range of attractive electrical and mechanical properties. This unique blend of properties make it a good candidate for emerging and future device technologies, such as sensors, high frequency electronics, and energy storage devices. In this review paper, each of the aforementioned applications will be explored along with demonstrations of their operating principles. Specifically, we explore pressure and humidity sensors, graphene base transistor for high frequency applications, and supercapacitors. In addition, this paper provides a general overview of these graphene technologies and, in the case of pressure and humidity sensors, benchmarking against other competing technologies. This paper further shows possible and prospective paths that are suitable for future graphene research to take.
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