| 1. |
- Adranno, Brando, et al.
(author)
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Broadband white-light-emitting electrochemical cells
- 2023
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In: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 4:5
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Journal article (peer-reviewed)abstract
- Emerging organic light-emitting devices, such as light-emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal-free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal-free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric-field-driven structural transformation of the original green-light emitter structure into a red-emitting structure.
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| 2. |
- Adranno, Brando, et al.
(author)
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The 8-hydroxyquinolinium cation as a lead structure for efficient color-tunable ionic small molecule emitting materials
- 2023
-
In: Advanced Photonics Research. - : John Wiley & Sons. - 2699-9293. ; 4:3
-
Journal article (peer-reviewed)abstract
- Albeit tris(8-hydroxyquinolinato) aluminum (Alq3) and its derivatives are prominent emitter materials for organic lighting devices, and the optical transitions occur among ligand-centered states, the use of metal-free 8-hydroxyquinoline is impractical as it suffers from strong nonradiative quenching, mainly through fast proton transfer. Herein, it is shown that the problem of rapid proton exchange and vibration quenching of light emission can be overcome not only by complexation, but also by organization of the 8-hydroxyquinolinium cations into a solid rigid network with appropriate counter-anions (here bis(trifluoromethanesulfonyl)imide). The resulting structure is stiffened by secondary bonding interactions such as pi-stacking and hydrogen bonds, which efficiently block rapid proton transfer quenching and reduce vibrational deactivation. Additionally, the optical properties are tuned through methyl substitution from deep blue (455 nm) to blue-green (488 nm). Time-dependent density functional theory (TDFT) calculations reveal the emission to occur from which an unexpectedly long-lived S-1 level, unusual for organic fluorophores. All compounds show comparable, even superior photoluminescence compared to Alq3 and related materials, both as solids and thin films with quantum yields (QYs) up to 40-50%. In addition, all compounds show appreciable thermal stability with decomposition temperatures above 310 °C.
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| 3. |
- Asadpoordarvish, Amir, et al.
(author)
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A Flexible Encapsulation Structure for Ambient-Air Operation of Light-Emitting Electrochemical Cells
- 2016
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In: Advanced Engineering Materials. - : Wiley. - 1438-1656 .- 1527-2648. ; 18:1, s. 105-110
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Journal article (other academic/artistic)abstract
- The emerging field of organic electronics is heralded because it promises low-cost and flexible devices, and it was recently demonstrated that a light-emitting electrochemical cell (LEC) can be fabricated with cost-efficient methods under ambient air. However, the LEC turns sensitive to oxygen and water during light-emission, and it is therefore timely to identify flexible encapsulation structures. Here, we demonstrate that a multilayer film, featuring a water and oxygen barrier property of ≈1 × 10–3 g/m2/day and ≈1 × 10–3 cm3/m2/bar/day respectively, is fit for this task. By sandwiching an LEC between such multilayer barriers, as attached by a UV-curable epoxy, we realize flexible LECs with performance on par with identical glass-encapsulated devices, and which remain functional after one year storage under air.
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| 4. |
- Asadpoordarvish, Amir, et al.
(author)
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Encapsulating light-emitting electrochemical cells for improved performance
- 2012
-
In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 100
-
Journal article (peer-reviewed)abstract
- We present a functional and scalable encapsulation of light-emitting electrochemical cells (LECs), which results in a measured ambient operation of >400 h at a brightness of >300 cd/m(2) with a maximum efficacy of 6 lm/W, and a linearly extrapolated ambient operation of similar to 5600 h at >100 cd/m(2). Our findings suggest that previous studies have underestimated the practical stability of appropriately encapsulated LECs. We also report that the dominant ambient degradation for non-encapsulated LECs is water-induced delamination of the cathode from the active layer, while encapsulated LECs in contrast are found to decay from spatial variations in the active layer composition. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4714696]
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| 5. |
- Asadpoordarvish, Amir, 1984-
(author)
-
Functional and Flexible Light-Emitting Electrochemical Cells
- 2015
-
Doctoral thesis (other academic/artistic)abstract
- The introduction of artificial illumination has brought extensive benefits to mankind, and during the last years we have seen a tremendous progress in this field with the introduction of the energy-efficient light-emitting diode (LED) and the high-contrast organic LED display. These high-end technologies are, however, produced using costly and complex processes, and it is anticipated that the next big thing in the field will be the advent of a low-cost and “green” illumination technology, which can be fabricated in a cost- and material-efficient manner using non-toxic and abundant raw materials, and which features attractive form factors such as flexibility, robustness and light-weight. The light-emitting electrochemical cell (LEC) is a newly invented illumination technology, and in this thesis we present results that imply that it can turn the above vision into reality.The thin-film LEC comprises an active material sandwiched between a cathode and an anode as its key constituent parts. With the aid of a handheld air-brush, we show that functional large-area LECs can be fabricated by simply spraying three layers of solution -- forming the anode, active material, and cathode -- on top of a substrate. We also demonstrate that such “spray-sintered” LECs can feature multicolored emission patterns, and be fabricated directly on complex-shaped surfaces, with one notable example being the realization of a light-emission fork!Almost all LECs up-to-date have been fabricated on glass substrates, but for a flexible and light-weight emissive device, it is obviously relevant to identify more appropriate substrate materials. For this end, we show that it is possible to spray-coat the entire LEC directly on conventional copy paper, and that such paper-LECs feature uniform light-emission even under heavy bending and flexing.We have further looked into the fundamental aspects of the LEC operation and demonstrated that the in-situ doping formation, which is a characteristic and heralded feature of LECs, can bring problems in the form of doping-induced self-absorption. By quantitatively analyzing this phenomenon, we provided straightforward guidelines on how future efficiency-optimized LEC devices should be designed.The in-situ doping formation process brings the important advantage that LECs can be fabricated from solely air-stabile materials, but during light emission the device needs to be protected from the ambient air. We have therefore developed a functional glass/epoxy encapsulation procedure for the attainment of LEC devices that feature a record-long ambient-air operational lifetime of 5600 h. For the light-emission device of the future, it is however critical that the encapsulation is flexible, and in our last study, we show that the use of multi-layer barrier can result in high-performance flexible LECs.
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| 6. |
- Asadpoordarvish, Amir, 1984-, et al.
(author)
-
Light-Emitting Paper
- 2015
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In: Advanced Functional Materials. - : Wiley. - 1616-301X .- 1616-3028. ; 25:21, s. 3238-3245
-
Journal article (peer-reviewed)abstract
- A solution-based fabrication of flexible and light-weight light-emitting devices on paper substrates is reported. Two different types of paper substrates are coated with a surface-emitting light-emitting electrochemical cell (LEC) device: a multilayer-coated specialty paper with an intermediate surface roughness of 0.4 μm and a low-end and low-cost copy paper with a large surface roughness of 5 μm. The entire device fabrication is executed using a handheld airbrush, and it is notable that all of the constituent layers are deposited from solution under ambient air. The top-emitting paper-LECs are highly flexible, and display a uniform light emission with a luminance of 200 cd m−2 at a current conversion efficacy of 1.4 cd A−1.
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| 7. |
- Auroux, Etienne, et al.
(author)
-
A metal-free and transparent light-emitting device by sequential spray-coating fabrication of all layers including PEDOT:PSS for both electrodes
- 2023
-
In: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 13:25, s. 16943-16951
-
Journal article (peer-reviewed)abstract
- The concept of a metal-free and all-organic electroluminescent device is appealing from both sustainability and cost perspectives. Herein, we report the design and fabrication of such a light-emitting electrochemical cell (LEC), comprising a blend of an emissive semiconducting polymer and an ionic liquid as the active material sandwiched between two poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) conducting-polymer electrodes. In the off-state, this all-organic LEC is highly transparent, and in the on-state, it delivers uniform and fast to turn-on bright surface emission. It is notable that all three device layers were fabricated by material- and cost-efficient spray-coating under ambient air. For the electrodes, we systematically investigated and developed a large number of PEDOT:PSS formulations. We call particular attention to one such p-type doped PEDOT:PSS formulation that was demonstrated to function as the negative cathode, as well as future attempts towards all-organic LECs to carefully consider the effects of electrochemical doping of the electrode in order to achieve optimum device performance.
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| 8. |
- Auroux, Etienne, et al.
(author)
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Evidence and Effects of Ion Transfer at Active-Material/Electrode Interfaces in Solution-Fabricated Light-Emitting Electrochemical Cells
- 2021
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In: Advanced Electronic Materials. - : Wiley-Blackwell Publishing Inc.. - 2199-160X. ; 7:8
-
Journal article (peer-reviewed)abstract
- The light-emitting electrochemical cell (LEC) allows for energy- and cost-efficient printing and coating fabrication of its entire device structure, including both electrodes and the single-layer active material. This attractive fabrication opportunity is enabled by the electrochemical action of mobile ions in the active material. However, a related and up to now overlooked issue is that such solution-fabricated LECs commonly comprise electrode/active-material interfaces that are open for transfer of the mobile ions, and it is herein demonstrated that a majority of the mobile anions in a common spray-coated active material can transfer into a spray-coated poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) positive electrode during LEC operation. Since it is well established that the mobile ion concentration in the active material has a profound influence on the LEC performance, this significant ion transfer is an important factor that should be considered in the design of low-cost LEC devices that deliver high performance.
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| 9. |
- Auroux, Etienne, et al.
(author)
-
Ion transfer into solution-processed electrodes can significantly shift the p-n junction and emission efficiency of light-emitting electrochemical cells
- 2022
-
In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 121:23
-
Journal article (peer-reviewed)abstract
- A light-emitting electrochemical cell (LEC) comprises mobile ions in its active material, which enable for in situ formation of a p-n junction by electrochemical doping. The position of this emissive p-n junction in the interelectrode gap is important, because it determines whether the emission is affected by constructive or destructive interference. An appealing LEC feature is that the entire device can be fabricated by low-cost solution-based printing and coating. Here, we show, somewhat unexpectedly, that the replacement of conventional vacuum-deposited indium-tin-oxide (ITO) for the positive anode with solution-processed poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) can result in an increase in the peak light-emission output by 75%. We demonstrate that this emission increase is due to that the p-n junction shifts from a position of destructive interference in the center of the interelectrode gap with ITO to a position of constructive interference closer to the anode with PEDOT:PSS. We rationalize the anodic p-n junction shift by significant anion transfer into the soft and porous PEDOT:PSS electrode during LEC operation, which is prohibited for the ITO electrode because of its compact and hard nature. Our study, thus, contributes with important design criteria for the attainment of efficient light emission from solution-processed LEC devices.
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| 10. |
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| 11. |
- Auroux, Etienne, et al.
(author)
-
Solution -based fabrication of the top electrode in light -emitting electrochemical cells
- 2020
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In: Organic electronics. - : Elsevier. - 1566-1199 .- 1878-5530. ; 84
-
Journal article (peer-reviewed)abstract
- The light-emitting electrochemical cell (LEC) has demonstrated capacity for cost- and material-efficient solution-based fabrication of the active material under ambient air. In this context, it is notable that corresponding reports on a scalable solution-based fabrication of the electrodes, particularly the top electrode, are rare. We address this issue through the demonstration of a transparent LEC, which is fabricated under ambient air by sequential spray deposition of a hydrophobic conjugated-polymer:ionic-liquid blend ink as the active material and a hydrophilic poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) ink as the transparent top electrode. Such an optimized LEC delivers a luminance of 360 cd/m2 at a power efficacy of 1.6 lm/W, which is on par with the performance of a corresponding LEC device equipped with a vacuum-deposited and reflective metal top electrode. This implies that the entire LEC device indeed can be fabricated with solution-based processes and deliver a good performance, which is critical if the LEC technology is going to fulfil its low-cost potential.
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| 12. |
- Auroux, Etienne, 1993-
(author)
-
Solution-processed light-emitting electrochemical cells : challenges and opportunities
- 2023
-
Doctoral thesis (other academic/artistic)abstract
- Our world is filling up with electronics. High-tech gadgets are integrated everywhere, from smart fridges able to track expiry dates and food usage, to microchip implants that let us unlock doors and pay with our hands. As innovative as they are, these new products and the many more to come impose new requirements on materials and fabrication methods. For instance, emerging electronic technologies that deliver light emission such as smart labels, authenticity features and light-based medical therapies, are often required to be flexible, see-through and low-cost, and in addition sustainable to fabricate, operate and recycle.In response to these challenges, the light-emitting industry is turning to organic electronics for solutions, a field that promises resource-efficient fabrication using environmentally benign materials. An interesting proposal is that of the light-emitting electrochemical cell (LEC), which, thanks to its simple structure, is well suitedfor high-throughput fabrication. The LEC is in many aspects a smart device, able to reorganize itself during operation via the electrochemical action of mobile ions, which create the injection and transport layers that require additional fabrication steps in other technologies. This elegant behavior makes the LEC tolerant to a large array of materials and fabrication methods, and hence a good fit for many applications.Yet the LEC is still today a scientific curiosity rather than an actual commercial solution and among the very few prototypes available on the market, none are able to meet the combined performance, resource efficiency and sustainability criteria. As a matter of fact, of the three layers that make an LEC, i.e., two electrodes surrounding an active material, only the later meet these requirements thanks to a strong recent research effort. In comparison, the electrodes have received little attention and are almost exclusively comprising metals or metal oxides deposited by time- and energy-expensive fabrication methods, making the LEC as a whole unfit for many applications.In an effort to push the LEC toward the untapped commercial niche of low-cost lighting, we tackle the problem of electrode fabrication with resource-efficiency in mind. We first show that up-scalable spray coating of inks under ambient air is a viable mean of fabrication for both active materials and electrodes alike. However, in doing so, we find that we create electrode interfaces that are open to ion transfer; an up-to-now overlooked issue that needs careful consideration when designing solution-processed LECs. Building on our discovery, we demonstrate that it is possible to fabricate an LEC entirely by using spray coating metal-free and organic inks; thereby demonstrating that an all-organic, metal-free and resource-efficient LEC is possible.I hope that our efforts will encourage others to work on solution-processed LECs, electrodes included, and develop ready-to-use products.
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| 13. |
- Barzegar, Hamid Reza, et al.
(author)
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Palladium nanocrystals supported on photo-transformed C-60 nanorods : effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation
- 2014
-
In: Carbon. - : Elsevier BV. - 0008-6223 .- 1873-3891. ; 73, s. 34-40
-
Journal article (peer-reviewed)abstract
- We report on the synthesis and decoration of high-aspect-ratio crystalline C-60 nanorods (NRs) by functionalized palladium nanoparticles with an average size of 4.78 +/- 0.66 nm. In their pristine form, C-60 NRs suffer from partial damage in the solution-based decoration process resulting in poor crystallinity. However, by modifying the NR surface via in situ photochemical transformation in the liquid state, we are able to prepare highly stable NRs that retain their crystalline structure during the decoration process. Our method thus opens up for the synthesis of highly crystalline nanocomposite hybrids comprising Pd nanoparticles and C-60 NRs. Bys measuring the electron mobility of different C-60 NRs, we relate both the effect of electron mobility and crystallinity to the final electrocatalytic performance of the synthesized hybrid structures. We show that the photo-transformed C-60 NRs exhibit highly advantageous properties for ethanol oxidation based on both a better crystallinity and a higher bulk conductivity. These findings give important information in the search for efficient catalyst support.
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| 14. |
- Barzegar, Hamid Reza, et al.
(author)
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Self-assembled PCBM nanosheets : a facile route to electronic layer-on-Layer heterostructures
- 2018
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In: Nano letters (Print). - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 18:2, s. 1442-1447
-
Journal article (peer-reviewed)abstract
- We report on the self-assembly of semicrystalline [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) nanosheets at the interface between a hydrophobic solvent and water, and utilize this opportunity for the realization of electronically active organic/organic molecular heterostructures. The self-assembled PCBM nanosheets can feature a lateral size of >1 cm2 and be transferred from the water surface to both hydrophobic and hydrophilic surfaces using facile transfer techniques. We employ a transferred single PCBM nanosheet as the active material in a field-effect transistor (FET) and verify semiconductor function by a measured electron mobility of 1.2 × 10–2 cm2 V–1 s–1 and an on–off ratio of ∼1 × 104. We further fabricate a planar organic/organic heterostructure with the p-type organic semiconductor poly(3-hexylthiophene-2,5-diyl) as the bottom layer and the n-type PCBM nanosheet as the top layer and demonstrate ambipolar FET operation with an electron mobility of 8.7 × 10–4 cm2 V–1 s–1 and a hole mobility of 3.1 × 10–4 cm2V–1 s–1.
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| 15. |
- Barzegar, Hamid Reza, et al.
(author)
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Solution-Based Phototransformation of C-60 Nanorods : Towards Improved Electronic Devices
- 2013
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In: Particle & particle systems characterization. - : Wiley-VCH Verlagsgesellschaft. - 0934-0866 .- 1521-4117. ; 30:8, s. 715-720
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Journal article (peer-reviewed)abstract
- A modified liquid-liquid interface precipitation synthesis of C-60 nanorods, effects and opportunities following an in situ photochemical transformation in the liquid state, and an electronic characterization using a field-effect transistor (FET) geometry are reported. The nanorods feature a high aspect ratio of approximate to 10(3) and a notably small average diameter of 172 nm. Interestingly, it is found that a decreased nanorod diameter appears to correlate with distinctly improved electronic properties, and an average electron mobility of 0.30 cm(2) V-1 s(-1), as measured in a FET geometry, is reported for as-grown nanorods, with the peak value being an impressive 1.0 cm(2) V-1 s(-1). A photoexposure using green laser light ( = 532 nm) is demonstrated to result in the formation of a polymer-C-60 shell encapsulating a monomer-C-60 bulk; such photo-transformed nanorods exhibit an electron mobility of 4.7 x 10(-3) cm(2) V-1 s(-1). It is notable that the utilized FET geometry only probes the polymer-C-60 nanorod surface shell, and that the monomer-C-60 bulk is anticipated to exhibit a higher mobility. Importantly, photoexposed nanorods can be conveniently processed as a stabile dispersion in common hydrophobic solvents, and this finding is attributed to the insoluble character of the polymer-C-60 shell.
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| 16. |
- Buga, Sergei G., et al.
(author)
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Semimetallic and semiconductor properties of some superhard and ultrahard fullerites in the range 300-2 K
- 2000
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In: Proceedings of the 5th IUMRS International Conference on Advanced Materials, Beijing 1999. - : Elsevier B.V.. ; , s. 1009-1015
-
Conference paper (peer-reviewed)abstract
- Electrical resistivity and magnetoresistance were measured on samples with disordered structures synthesized from pure C60 and C70 at pressures in the range 8–12.5 GPa and temperatures of 900–1500 K. Different types of behaviour were observed: semimetallic, VRH and semiconducting, depending on the degree of disorder and the particular short-range order of the samples. A negative magnetoresistance was observed at T<10 K on samples with a semimetallic type of conductivity synthesized at 8 GPa pressure. The temperature dependence of resistivity in the sample with a disordered crystalline structure based on 3D-polymerized C60 molecules fits Mott's law for hopping conductivity. T3/2, T2 and T4 dependencies of conductivity are observed for samples with densities of 2.8 and 3.05 g/cm3 synthesized at a pressure of 12.5 GPa. The effect of hydrostatic pressure on the resistivity of cross-linked layered carbon structures obtained from C60 at P=8 GPa, T=1600 K was investigated up to 0.6 GPa at room temperature. An approximately linear decrease of resistivity was observed with a very small value of the derivative d ln ρ/dp=0.06 /GPa, which correlates with a very low compressibility of the material.
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| 17. |
- Bychkov, Vitaly, 1968-, et al.
(author)
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Speedup of doping fronts in organic semiconductors through plasma instability
- 2011
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In: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:1, s. 016103-016107
-
Journal article (peer-reviewed)abstract
- The dynamics of doping transformation fronts in organic semiconductor plasma is studied for application in light-emitting electrochemical cells. We show that new fundamental effects of the plasma dynamics can significantly improve the device performance. We obtain an electrodynamic instability, which distorts the doping fronts and increases the transformation rate considerably. We explain the physical mechanism of the instability, develop theory, provide experimental evidence, perform numerical simulations, and demonstrate how the instability strength may be amplified technologically. The electrodynamic plasma instability obtained also shows interesting similarity to the hydrodynamic Darrieus-Landau instability in combustion, laser ablation, and astrophysics.
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| 18. |
- Dahlberg, Tobias, et al.
(author)
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3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers
- 2018
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In: Scientific Reports. - : Nature Publishing Group. - 2045-2322. ; 8:1
-
Journal article (peer-reviewed)abstract
- We report a novel method for fabrication of three-dimensional (3D) biocompatible micro-fluidic flow chambers in polydimethylsiloxane (PDMS) by 3D-printing water-soluble polyvinyl alcohol (PVA) filaments as master scaffolds. The scaffolds are first embedded in the PDMS and later residue-free dissolved in water leaving an inscription of the scaffolds in the hardened PDMS. We demonstrate the strength of our method using a regular, cheap 3D printer, and evaluate the inscription process and the channels micro-fluidic properties using image analysis and digital holographic microscopy. Furthermore, we provide a protocol that allows for direct printing on coverslips and we show that flow chambers with a channel cross section down to 40 x 300 μm can be realized within 60 min. These flow channels are perfectly transparent, biocompatible and can be used for microscopic applications without further treatment. Our proposed protocols facilitate an easy, fast and adaptable production of micro-fluidic channel designs that are cost-effective, do not require specialized training and can be used for a variety of cell and bacterial assays. To help readers reproduce our micro-fluidic devices, we provide: full preparation protocols, 3D-printing CAD files for channel scaffolds and our custom-made molding device, 3D printer build-plate leveling instructions, and G-code.
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| 19. |
- Doeff, Marca M., et al.
(author)
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A high-rate manganese oxide for rechargeable lithium battery applications
- 2001
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In: Journal of the Electrochemical Society. - : Electrochemical Society Inc. - 0013-4651 .- 1945-7111. ; 148:3, s. A230-A236
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Journal article (peer-reviewed)abstract
- LixMnO2 made by ion exchange of glycine-nitrate combustion synthesis-processed (GNP) orthorhombic Na0.44MnO2 (GNP-LixMnO2) has been cycled in lithium/liquid electrolyte cell configurations at room temperature and lithium/polymer cell configurations at 85 degreesC over one hundred times without showing capacity fading or phase conversion to spinel. At 2.5 mA/cm2 in liquid cells (5C rate) or 1 mA/cm2 (1.5C rate) in polymer cells, 80-95% of the expected capacity is delivered. The remarkable stability is attributable to the unusual double tunnel structure, which cannot easily undergo rearrangement to spinel. The enhanced rate capability of GNP-LixMnO2 compared to conventionally prepared materials is attributable to the shorter particle length, which allows faster diffusion of lithium ions along the tunnels.
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| 20. |
- Doeff, M.M, et al.
(author)
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Transport properties of binary salt polymer electrolytes
- 2000
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In: Journal of Power Sources. - : Elsevier. - 0378-7753 .- 1873-2755. ; 89:2, s. 227-231
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Journal article (peer-reviewed)abstract
- Transport properties (ionic conductivities (σ), salt diffusion coefficients (Ds), and cationic transference numbers (t+0)) as a function of salt concentration (Cs) are reported and compared for several common binary salt/polymer systems being considered for use as electrolytes in rechargeable lithium batteries for electric vehicle and other applications. The three properties provide a complete description of transport in solid polymer electrolytes (SPEs) or "dry" systems in cells undergoing galvanostatic charge and discharge. The macroscopic approach used obviates the need to know the details of speciation in these non-ideal solutions and allows for a more sophisticated correlation of the characteristics of ion transport with polymer structure, salt type, and concentration than conductivity data alone.
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| 21. |
- dos Santos, John Marques, et al.
(author)
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Color tuning of multi-resonant thermally activated delayed fluorescence emitters based on fully fused polycyclic amine/carbonyl frameworks
- 2023
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In: Journal of Materials Chemistry C. - : Royal Society of Chemistry. - 2050-7526 .- 2050-7534. ; 11:24, s. 8263-8273
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Journal article (peer-reviewed)abstract
- Two novel π-extended amine/carbonyl-based multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have been designed and synthesized. The two emitters are isomeric, composed of nine fused rings and show green-yellow emission. Sym-DiDiKTa and Asym-DiDiKTa possess tert-butyl groups distributed in a symmetrical and asymmetrical fashion, respectively, which significantly impact the single-crystal packing structure. The two compounds possess similar singlet-triplet energy gaps, ΔEST, of around 0.23 eV, narrowband emission characterized by a full-width at half-maximum, FWHM, of 29 nm and a photoluminescence quantum yield, ΦPL, of 70% and 53% for the symmetric and asymmetric counterparts, respectively, in toluene. Investigation in OLEDs demonstrated that the devices with Sym-DiDiKTa and Asym-DiDiKTa displayed electroluminescence maxima of 543 and 544 nm, and maximum external quantum efficiencies (EQEmax) of 9.8% and 10.5%, respectively. The maximum EQE was further improved to 19.9% by employing a hyperfluorescence strategy. We further present the first example of a neutral MR-TADF emitter incorporated in a LEC device where Sym-DiDiKTa acts as the emitter. The LEC shows a λEL at 551 nm and FWHM of 60 nm with luminance of 300 cd m−2 and a fast turn-on time of less than 2 s to 100 cd m−2
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| 22. |
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| 23. |
- Dzwilewski, Andrzej, et al.
(author)
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C60 Field-Effect Transistors: Effects of Polymerization on electronic Properties and Device Performance.
- 2007
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In: Physical Review B. ; 75:7, s. 075203-
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Journal article (peer-reviewed)abstract
- We have investigated thin-film field-effect transistors (TFTs) with C60 as the active material, and we report the effects of photo-induced polymerization of the C60 film. We find that the effects of a complete polymerization for a typical top-contact C60 TFT is as follows: the electron mobility (μn) at room temperature drops slightly from 0.074 to 0.068 cm2/Vs, the activation energy of μn decreases from 0.10 meV to 0.09 meV, and the threshold voltage for TFT operation decreases markedly by ~15 %. The latter observation suggests that the effective number of electron traps in the C60 film decreases following polymerization. Considering that the polymerization was achieved with a low-energy HeNe laser, it is conceivable that the polymerization approach could be of interest for applications, e.g., organic bulk-heterojunction solar cells, where a stabilized C60 morphology attained with benign means is desired
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| 24. |
- Dzwilewski, Andrzej, et al.
(author)
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Facile fabrication of efficient organic CMOS circuits
- 2010
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 114:1, s. 135-140
-
Journal article (peer-reviewed)abstract
- Organic electronic circuits based on a combination of n- and p-type transistors (so-called CMOS circuits) are attractive, since they promise the realization of a manifold of versatile and low-cost electronic devices. Here, we report a novel photoinduced transformation method, which allows for a particularly straightforward fabrication of highly functional organic CMOS circuits. A solution-deposited single-layer film, comprising a mixture of the n-type semiconductor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and the p-type semiconductor poly-3-hexylthiophene (P3HT) in a 3:1 mass ratio, was utilized as the common active material in an array of transistors. Selected film areas were exposed to laser light, with the result that the irradiated PCBM monomers were photochemically transformed into a low-solubility and high-mobility dimeric state. Thereafter, the entire film was developed via immersion into a developer solution, which selectively removed the nonexposed, and monomeric, PCBM component. The end result was that the transistors in the exposed film areas are n-type, as dimeric PCBM is the majority component in the active material, while the transistors in the nonexposed film areas are p-type, as P3HT is the sole remaining material. We demonstrate the merit of the method by utilizing the resulting combination of n-type and p-type transistors for the realization of CMOS inverters with a high gain of ∼35.
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| 25. |
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| 26. |
- Dzwilewski, Andrzej, 1979-, et al.
(author)
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Facile fabrication of organic CMOS circuits via photo-induced imprinting of a single-layer blend
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Other publication (other academic/artistic)abstract
- Organic electronic circuits based on a combination of n- and p-type transistors (so-called CMOS circuits) are attractive, since they promise the realization of a manifold of versatile and low-cost electronic devises. Here, we report a novel photo-induced imprinting method, which allows for a particularly straightforward fabrication of highly functional organic CMOS circuits. A single-layer blend film, comprising a mixture of the n-type semiconductor [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) and the p-type semicondutor poly-3-hexylthiophene (P3HT) in a 3:1 mass ratio, was deposited from solution onto an array of transistor structures on a substrate. By exposing select film areas to laser light, the PCBM monomers were photo-chemically transformed into a low-solubility and high-mobility dimeric state. Thereafter, the entire film was developed by immersing the substrate into a developer solution, which selectively removed the non-exposed, and monomeric, PCBM. The end result was that the transistors in the exposed areas are n-type, as dimeric PCBM is the majority component, while the transistors in the non-exposed areas are p-type, as P3HT is the sole remaining material. We demonstrate the merit of the method by utilizing the combination of n-type and p-type transistors for the realization of CMOS inverters with a high gain of ~35.
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| 27. |
- Dzwilewski, Andrzej, 1979-, et al.
(author)
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Photo-induced and resist-free imprint patterning of fullerene materials for use in functional electronics
- 2009
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In: Journal of the American Chemical Society. - Washington, DC, USA : American Chemical Society. - 0002-7863 .- 1520-5126. ; 131:11, s. 4006-4011
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Journal article (peer-reviewed)abstract
- We report a novel and potentially generic method for the efficient patterning of films of organic semiconductors and demonstrate the merit of the method on the high-solubility fullerene [6,6]-phenyl C61- butyric acid methyl ester (PCBM). The patterning technique is notably straightforward as it requires no photoresist material and encompasses only two steps: (i) exposure of select film areas to visible laser light during which the PCBM mononer is photochemically converted into a dimeric state, and (ii) development via solvent washing after which the nonexposed portions of the PCBM film are selectively removed. Importantly, the method is highly benign in that it leaves the electronic properties of the remaining patterned material intact, which is directly evidenced by the fact that we fabricate fully functional arrays of micrometersized field-effect transistors with patterned PCBM as the active material.
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| 28. |
- Dzwilewski, Andrzej, 1979-
(author)
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Photo-polymerization as a tool for engineering the active material in organic field-effect transistors
- 2009
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Doctoral thesis (other academic/artistic)abstract
- The emergence of organic semiconductors is exciting since it promises to open up for straightforward and low-cost fabrication of a wide range of efficient and novel electronic devices. However, in order for this promise to become reality it is critical that new and functional fabrication techniques are developed. This thesis demonstrates the conceptualization, development, realization and implementation of a particularly straightforward and scalable fabrication process: the photo-induced and resist-free imprint patterning technique.Initial experiments revealed that some members of a group of carbon-cage molecular semiconductors – termed fullerenes – can be photochemically modified into dimeric or polymeric structures during exposure to laser light, and, importantly, that the exposed fullerene material retains its good electron-transport property while its solubility in common organic solvents is drastically lowered. With this information at hand, it was possible to design and create well-defined patterns in a solution-deposited fullerene film by exposing selected film areas to laser light and then developing the entire film in a tuned developer solution. An electronically active fullerene pattern emerges at the locations defined by the incident laser beam, and the patterning technique was successfully utilized for the fabrication of arrays of efficient field-effect transistors.In a later stage, the capacity of the photo-induced and resist-free imprint technique was demonstrated to encompass the fabrication of ubiquitous and useful CMOS circuits. These are based on a combination of p-type and n-type transistors, and a blend between a p-type organic semiconductor and an n-type fullerene compound was designed so that the latter dominated. By solution-depositing the blend film on an array of transistor structures, exposing selected transistors to laser light, and then developing the entire transistor array in a developer solution, it was possible to establish a desired combination of (non-exposed) p-type transistors and (exposed) n-type transistors. We finally utilized this combination of transistors for the fabrication of a CMOS circuit in the form of well a-functional organic inverter stage.
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| 29. |
- Edman, Ludvig, et al.
(author)
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Analysis of diffusion in a solid polymer electrolyte in the context of a phase-separated system
- 2002
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In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics. - : American Physical Society. - 1539-3755 .- 1550-2376. ; 65:4, s. 042803-1-042803-4
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Journal article (peer-reviewed)abstract
- The salt and ionic diffusion coefficients of the salt LiN(CF3SO2)2 (LiTFSI) dissolved in high-molecular-weight poly(ethylene oxide) [PEO] have been measured over a broad concentration range, and the interrelationship of the measured values is demonstrated to be in good agreement with basic electrochemical theory. In the light of recently published structural findings, we propose a biphasic model for the conducting amorphous state, consisting of a stoichiometric P(EO)6LiTFSI phase dispersed into a salt-containing disordered phase, and analyze the ionic diffusion data within the framework of the Bruggeman-Landauer theory. The agreement between experimental and fitted data is shown to be excellent. We conclude by pointing out and discussing potential weaknesses of our analysis.
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| 30. |
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| 31. |
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| 32. |
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| 33. |
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| 34. |
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| 35. |
- Edman, Ludvig, 1967-, et al.
(author)
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Effect of C60 as a Filler on the Morphology of Polymer−Salt Complexes Based on Poly(ethylene oxide) and LiCF3SO3
- 1999
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In: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 32:12, s. 4130-4133
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Journal article (peer-reviewed)abstract
- The inclusion of C60 as a filler in complexes of paly(ethylene oxide) (PEO) and LiCF3SO3 salt reduces the degree of crystallinity of the material at ambient temperature. The observed effects are manifested as changes in characteristic vibrational modes of the crystalline polymer in FT-Raman spectra over a range of temperatures. The introduction of relatively small amounts of C60 also stabilizes ionic substructures present in these systems. Interestingly, no internal modes of the C60 molecule are affected by dissolution in PEO or by the presence of varying amounts of LiCF3SO3 salt in the matrix. From the absence of a shift in the C60:s charge-transfer-sensitive Ag(2) mode, in particular, it appears as though C60 essentially acts as an inert filler in these complexes.
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| 36. |
- Edman, Ludvig, et al.
(author)
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Electrical resistivity of single crystal graphite under pressure: an anisotropic 3-D semimetal
- 1998
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In: Physical Review B. Condensed Matter and Materials Physics. - : American Physical Society. - 1098-0121 .- 1550-235X. ; 57:11, s. 6227-6230
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Journal article (peer-reviewed)abstract
- The in-plane (ρa) and c-axis (ρc) resistivities of natural single-crystal graphite have been measured from 4 to 450 K at zero pressure and from 77 to 450 K under pressures up to 500 MPa. Data for ρc differ strongly from earlier results obtained on synthetic graphite in showing a strong T dependence of the pressure coefficient, while data for ρa agree well with those from previous studies. Our results can be analyzed quantitatively in a simple free-electron model, and we conclude that in contrast to quasi-two-dimensional synthetic graphite, natural single-crystal graphite is an anisotropic three-dimensional semimetal.
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| 37. |
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| 38. |
- Edman, Ludvig, 1967-, et al.
(author)
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Influence of the anion on the kinetics and stability of a light-emitting electrochemical cell
- 2003
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In: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 138:3, s. 441-446
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Journal article (peer-reviewed)abstract
- The selection of the anion is shown to be crucial for the response time and the lifetime of light-emitting electrochemical cells (LECs) fabricated with [co-block phenyl-substituted poly(para phenylene vinylene)]-PEO-LiX (X = Tf, TFSI, Tf-TFSI). With a mixed-anion (X = Tf-TFSI) salt. the LEC turned on in less than 0.4 s at ΔU = 4.0 V, with X = TFS1 it turned on in a few seconds, while X = Tf produced devices with significantly larger response times with a strong dependence on the film thickness. We attribute this significant variation in the response to the morphology of the PEO-LiX phase at room temperature: PEO-LiTf is largely crystalline with a correspondingly limited ionic mobility: PEO-LiTf-TFSI is amorphous with a relatively high mobility; and heat-treated PEO-LiTFSI is typically partially amorphous. For lifetimes. we focused on 3.0 ≤ ΔU ≤ 4.0 V since this range coincided with a crossover in performance for the X = Tf devices. At ΔU = 3.0 V, these lasted the entire measurement cycle (=55 h) with constant efficiency and only a small decrease in light output. At ΔU ≥ 3.25 V. the same devices exhibited a limited lifetime with a linear dependence on the salt concentration and a decrease in the efficiency with time. For X = TFSI. Tf-TFSI short lifetimes and a decrease in efficiency with time were obtained independent of the applied voltage. Considering recently published data on electrochemical stability, we propose that an irreversible overreduction of the anion is a significant side reaction that limits the lifetime of LEC systems.
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| 39. |
- Edman, Ludvig, 1967-
(author)
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Ion Association and Ion Solvation Effects at the Crystalline−Amorphous Phase Transition in PEO−LiTFSI
- 2000
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In: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 104:31, s. 7254-7258
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Journal article (peer-reviewed)abstract
- From band shape analyses of the strong 740 cm-1 Raman mode of the TFSI anion, we deduce that the crystalline state of the P(EO)nLiTFSI system contains a very small amount of ion pairs (approximate to 7%), most probably belonging to the minor amorphous phase, for the n greater than or equal to 6 range. For all-amorphous samples, we found a small amount of ion pairs for n greater than or equal to 8, but a significant amount (approximate to 24%) for n = 6. This increase in ion pair formation coincides with a decrease in the relative solvation of lithium cations by polymeric ether oxygens, as detected from a careful study of the 863 cm-1 polymer-cation "breathing mode". We therefore propose that the local ionic structure is preserved during the melting of n greater than or equal to 8 compositions, but that there is a changeover from a predominately ether oxygen lithium coordination to a combined ether oxygen and anionic coordination of the lithium cations for more concentrated samples upon melting.
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| 40. |
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| 41. |
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| 42. |
- Edman, Ludvig, et al.
(author)
-
On-demand photochemical stabilization of doping in light-emitting electrochemical cells
- 2011
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In: Electrochimica Acta. - : Elsevier. - 0013-4686 .- 1873-3859. ; 56:28, s. 10473-10478
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Journal article (peer-reviewed)abstract
- A highly functional p-n junction doping structure can be realized within a light-emitting electrochemical cell under applied voltage via ion redistribution and electrochemical doping. This doping structure will however dissipate when the formation voltage is removed due to the mobility of the dopant counter-ions. A number of concepts aimed at a spatial immobilization of the ions and the related stabilization of the doping structure have been presented, but they all suffer from long and poorly controlled stabilization periods and/or unpractical operational conditions. Here, we ntroduce a markedly fast and easy-to-control stabilization procedure involving the inclusion of a UV-sensitive photo-initiator compound into a carefully tuned active material in an light-emitting electrochemical cell device, and demonstrate that it is possible to cross-link the ions and stabilize the p-n junction doping via a short UV exposure step executed at room temperature. 1.
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| 43. |
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| 44. |
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| 45. |
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| 46. |
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| 47. |
- Edman, Ludvig, 1967-, et al.
(author)
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Single-component light-emitting electrochemical cell with improved stability
- 2003
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In: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 82:22, s. 3961-3963
-
Journal article (peer-reviewed)abstract
- We report a single-component polymeric light-emitting electrochemical cell with poly[9,9'-bis[6"-(N, N, N-trimethylammonium)hexyl]fluorene-alt-co-phenylene]bromide (PFN+Br-) as the active material. Indium tin oxide/PFN+Br-/aluminum sandwich structures demonstrate a low and thickness-independent turn-on voltage (2.9 V) for blue light emission. Thermophysical characterization shows that PFN+Br- is in a metastable amorphous phase after spin casting, but that crystallization takes place at elevated temperatures. With this information at hand, we allowed devices to turn-on via ionic redistribution (and the formation of a p-i-n junction) in the amorphous phase, and then stabilized this desired configuration through crystallization. We find significantly improved lifetimes and relatively fast turn-on times for these single-component devices operating at room temperature.
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| 48. |
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| 49. |
- Edman, Ludvig, 1967-, et al.
(author)
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Slow recrystallization in the polymer electrolyte system poly(ethylene oxide)n–LiN(CF3SO2)2
- 2000
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In: Journal of Materials Research. - : Materials Research Society. - 0884-2914 .- 2044-5326. ; 15:9, s. 1950-1954
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Journal article (peer-reviewed)abstract
- Thermal and ion-transport properties of the salt-in-polymer system poly(ethylene oxide)n-LiN(CF3SO2)2 [P(EO)nLiTFSI] were investigated for compositions ranging from n =5 to n = 50. Particular attention was paid to the region n = 8 to 10 where a crystallinity gap previously had been reported. We concluded that the absence of distinct melting transitions for salt-rich compositions (n = 5 to 12) was attributable to the extremely slow kinetics of recrystallization of this system following a heat treatment. The results further indicated that it was primarily the nucleation process that was inhibited by the [(bis)trifluoromethanesulfonate imide] (TFSI) anion. As a corollary, the ionic conductivity was strongly dependent on the thermal history of samples, and an enhancement of up to 300% was observed in the ambient temperature ionic conductivity for pre-heated salt-rich samples.
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| 50. |
- Edman, Ludvig, et al.
(author)
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Sodium-sodium halide co-intercalated graphite: chemistry, structure and electrical transport
- 1999
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In: Journal of Physics and Chemistry of Solids. - : Elsevier B.V.. - 0022-3697 .- 1879-2553. ; 60:4, s. 475-482
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Journal article (peer-reviewed)abstract
- This study deals with the second to fourth stage compounds resulting from the co-intercalation of sodium and sodium halides into graphite. The charge transfer was determined through chemical analyses and X-ray diffraction and the results are compatible with Raman spectroscopy data. We present detailed results on c axis conduction between 4.2 K and 295 K and for hydrostatic pressures as high as 1.6 GPa. Possible mechanisms explaining the c axis conduction are discussed.
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