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  • 1.
    Asadpoordarvish, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Andreas
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    A Flexible Encapsulation Structure for Ambient-Air Operation of Light-Emitting Electrochemical Cells2016Inngår i: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 18, nr 1, s. 105-110Artikkel i tidsskrift (Annet vitenskapelig)
    Abstract [en]

    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.

  • 2.
    Asadpoordarvish, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC, Umeå, Sweden.
    Sandström, Andreas
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Bollström, Roger
    Toivakka, Martti
    Österbacka, Ronald
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Light-Emitting Paper2015Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 25, nr 21, s. 3238-3245Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 3.
    Asadpoordarvish, Amir
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Andreas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tang, Shi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Granström, Jimmy
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Encapsulating light-emitting electrochemical cells for improved performance2012Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, artikkel-id 193508Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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]

  • 4.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hu, Guangzhi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Jia, Xueen
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation2014Inngår i: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, s. 34-40Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 5.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Department of Physics, University of California, Berkeley, California 94720, United States ‡ Department of Physics, Umeå University, SE-901 87 Umeå, Sweden § Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States ∥ Kavli Energy NanoSciences Institute at the University of California, Berkeley and the Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Boulanger, Nicolas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zettl, Alex
    Department of Physics, University of California, Berkeley, California 94720, United States.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Self-assembled PCBM nanosheets: a facile route to electronic layer-on-Layer heterostructures2018Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 2, s. 1442-1447Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 6.
    Barzegar, Hamid Reza
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Solution-Based Phototransformation of C-60 Nanorods: Towards Improved Electronic Devices2013Inngår i: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, nr 8, s. 715-720Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 7. Buga, Sergei G.
    et al.
    Blank, Vladimir D.
    Dubitsky, Gennadii A.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zhu, Xiaomei
    Nyeanchi, Emmanuel B.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Semimetallic and semiconductor properties of some superhard and ultrahard fullerites in the range 300-2 K2000Inngår i: Proceedings of the 5th IUMRS International Conference on Advanced Materials, Beijing 1999, Elsevier B.V. , 2000, s. 1009-1015Konferansepaper (Fagfellevurdert)
    Abstract [en]

    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.

  • 8.
    Bychkov, Vitaly
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Akkerman, Vyacheslav
    Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA.
    Modestov, Mikhail
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Valiev, Damir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brodin, Gert
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Law, Chung K.
    Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, New Jersey 08544-5263, USA.
    Marklund, Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Speedup of doping fronts in organic semiconductors through plasma instability2011Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 107, nr 1, s. 016103-016107Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 9.
    Dahlberg, Tobias
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Stangner, Tim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Hanqing, Zhang
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wiklund, Krister
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lundberg, Petter
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers2018Inngår i: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, nr 1, artikkel-id 3372Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 10.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Facile fabrication of efficient organic CMOS circuits2010Inngår i: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 114, nr 1, s. 135-140Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 11.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Moons, Ellen
    Karlstad universitet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Facile fabrication of organic CMOS circuits: understanding and optimization of the processManuskript (Annet vitenskapelig)
  • 12.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    C60 Field-Effect Transistors: Effects of Polymerization on Electronic Properties and Device Performance.2007Inngår i: Extended abstracts – 9th European Conference on Molecular Electronics, 2007Konferansepaper (Annet vitenskapelig)
  • 13.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    C60 Field-Effect Transistors: Effects of Polymerization on electronic Properties and Device Performance.2007Inngår i: Physical Review B, Vol. 75, nr 7, s. 075203-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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

  • 14.
    Dzwilewski, Andrzej
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Photo-induced and resist-free imprint patterning of fullerene materials for use in functional electronics2009Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 131, nr 11, s. 4006-4011Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 15.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Bringing Light to Polymer Electrolytes: The Light-Emitting Electrochemical Cell.2004Inngår i: Extended Abstracts – The Ninth International Symposium on Polymer Electrolytes, 2004Konferansepaper (Annet vitenskapelig)
  • 16.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Bringing Light to Solid-State Electrolytes: The Polymer Light-Emitting Electrochemical Cell2005Inngår i: Electrochimica Acta, Vol. 50, s. 3878-3885Artikkel i tidsskrift (Fagfellevurdert)
  • 17.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Conjugated Polymers - Novel Concepts for Functional Electronics.2008Inngår i: Extended abstracts – Nordic Polymer Days, 2008, s. 2-Konferansepaper (Annet vitenskapelig)
  • 18.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Funktionella mönster av organisk elektronik.2009Inngår i: Fysikaktuellt, ISSN 0283-9148, Vol. 4, s. 8-Artikkel, forskningsoversikt (Annet (populærvitenskap, debatt, mm))
  • 19.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Organisk Elektronik – En Flexibel Revolution.2008Inngår i: Thule, Skytteanska samfundets årsskrift, 2008, s. 115-130Kapittel i bok, del av antologi (Annet (populærvitenskap, debatt, mm))
  • 20.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    The Light-Emitting Electrochemical Cell2010Inngår i: Iontronics – Ionic Carriers in Organic Electronic Materials and Devices / [ed] J. Leger, M. Berggren, and S. Carter, Boca Raton, FL (US): CRC Press , 2010, 1, s. 101-118Kapittel i bok, del av antologi (Fagfellevurdert)
  • 21.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    The Light-Emitting Electrochemical Cell: Utilizing Ions for Self Assembly and Improved Device Operation2011Inngår i: Functional Supramolecular Architectures / [ed] Paolo Samori and Franco Cacialli, Weinheim (Germany): WILEY-VCH Verlag , 2011, 1, s. 895-917Kapittel i bok, del av antologi (Fagfellevurdert)
  • 22.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Ferry, Anders
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Orädd, Greger
    Kemi.
    Analysis of diffusion in a solid polymer electrolyte in the context of a phase-separated system2002Inngår i: Physical Review E 65, 042803, nr 4, s. 1-4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 23.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Hérold, A.
    Jacobsson, Per
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Lelaurain, Michelle
    McRae, Edward
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sodium-sodium halide co-intercalated graphite: chemistry, structure and electrical transport1999Inngår i: Journal of Physics and Chemistry of Solids, ISSN 0022-3697, E-ISSN 1879-2553, Vol. 60, nr 4, s. 475-482Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 24.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Liu, B.
    Vehse, M.
    Swensen, J.
    Bazan, G.C.
    Heeger, Alan J.
    Single-Component Light-Emitting Electrochemical Cell Fabricated From Cationic Polyfluorene: Effect of Film Morphology on Device Performance2005Inngår i: Journal of Applied Physics, Vol. 98, nr 4, s. 044502-Artikkel i tidsskrift (Fagfellevurdert)
  • 25.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Liu, Bin
    Pauchard, Marc
    Moses, Daniel
    Bazan, Guillermo C.
    Heeger, Alan J.
    Single-Component Polymer Light-Emitting Electrochemical Cell.2005Inngår i: Extended Abstracts – The 5th International Conference on Electroluminescence of Molecular Materials and Related Phenomena, 2005, s. 119-120Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 26.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Shin, Joon Ho
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Andersson, Mats
    Light-emitting Electrochemical Cells with mm-sized Electrode Gap: Controlling Light at Low Voltage and Identification of Degradation Mechanism.2008Inngår i: SPIE Photonics Europe, 2008Konferansepaper (Annet vitenskapelig)
  • 27.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Pauchard, M.
    Moses, D.
    Heeger, Alan J.
    Planar Polymer Light-Emitting Device with Fast Kinetics at a Low Voltage2004Inngår i: Journal of Applied Physics, Vol. 95, s. 4357-61Artikkel i tidsskrift (Fagfellevurdert)
  • 28.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Shin, Joon Ho
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Andersson, Mats R.
    Robinson, Nathaniel D.
    Direct Optical Probing of Doping Progression and Light Emission in Planar Light-Emitting Electrochemical Cells with mm-Sized Electrode Gaps.2007Inngår i: Extended abstracts – 7th International Conference on Optical Probes of π-Conjugated Polymers and Functional Self Assemblies, 2007Konferansepaper (Annet vitenskapelig)
  • 29.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Shin, Joon Ho
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Robinson, Nathaniel D.
    Berggren, Magnus
    Xiao, Steven
    Light-Emitting Electrochemical Cells: Direct Probing of Doping Progression and Emission2006Inngår i: Extended abstracts – 57th Annual Meeting of the International Society of Electrochemistry, 2006, s. S7-KNKonferansepaper (Annet vitenskapelig)
  • 30.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Summers, M.A.
    Burrato, S.K.
    Heeger, Alan J.
    Polymer Light-Emitting Electrochemical Cells: Doping, Luminescence and Mobility2004Inngår i: Physical Review B, Vol. 70, s. 115212-Artikkel i tidsskrift (Fagfellevurdert)
  • 31.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    McRae, Edward
    C-axis resistivity of single crystal graphite under high pressure1996Inngår i: Extended Abstracts of Carbon´96, European Carbon Conference, Newcastle-upon-Tyne 1996, volume 2, The British Carbon Group , 1996, s. 493-494Konferansepaper (Annet vitenskapelig)
  • 32.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Sundqvist, Bertil
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    McRae, Edward
    Litvin-Staszewska, E.
    Electrical resistivity of single crystal graphite under pressure: an anisotropic 3-D semimetal1998Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 57, nr 11, s. 6227-6230Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 33.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Swensen, J.
    Moses, D.
    Heeger, Alan J.
    Toward Improved and Tunable Polymer Field-Effect Transistors2004Inngår i: Applied Physics Letters, Vol. 84, s. 3744-3746Artikkel i tidsskrift (Fagfellevurdert)
  • 34.
    Edman, Ludvig
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Tang, Shi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    On-demand photochemical stabilization of doping in light-emitting electrochemical cells2011Inngår i: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, nr 28, s. 10473-10478Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    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.

  • 35. Ekeroth, Sebastian
    et al.
    Münger, E. Peter
    Boyd, Robert
    Ekspong, Joakim
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Brenning, Nils
    Helmersson, Ulf
    Catalytic nanotruss structures realized by magnetic self-assembly in pulsed plasma2018Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 5, s. 3132-3137Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Tunable nanostructures that feature a high surface area are firmly attached to a conducting substrate and can be fabricated efficiently over significant areas, which are of interest for a wide variety of applications in, for instance, energy storage and catalysis. We present a novel approach to fabricate Fe nanoparticles using a pulsed-plasma process and their subsequent guidance and self-organization into well-defined nanostructures on a substrate of choice by the use of an external magnetic field. A systematic analysis and study of the growth procedure demonstrate that nondesired nanoparticle agglomeration in the plasma phase is hindered by electrostatic repulsion, that a polydisperse nanoparticle distribution is a consequence of the magnetic collection, and that the formation of highly networked nanotruss structures is a direct result of the polydisperse nanoparticle distribution. The nanoparticles in the nanotruss are strongly connected, and their outer surfaces are covered with a 2 nm layer of iron oxide. A 10 μm thick nanotruss structure was grown on a lightweight, flexible and conducting carbon-paper substrate, which enabled the efficient production of H2 gas from water splitting at a low overpotential of 210 mV and at a current density of 10 mA/cm2.

  • 36.
    Enevold, Jenny
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Zakrisson, Johan
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Andersson, Magnus
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Realizing large-area arrays of semiconducting fullerene nanostructures with direct laser interference patterning2018Inngår i: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, nr 1, s. 540-545Artikkel i tidsskrift (Fagfellevurdert)
  • 37.
    Fang, Junfeng
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    The design and realization of flexible light-emitting electrochemical cells with record-long lifetime2009Inngår i: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 19, nr 16, s. 2671-2676Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Polymer light-emitting electrochemical cells (LECs) offer an attractive opportunity for low-cost production of functional devices in flexible and large-area configurations, but the critical drawback in comparison to competing light-emission technologies is a limited operational lifetime. Here, it is demonstrated that it is possible to improve the lifetime by straightforward and motivated means from a typical value of a few hours to more than one month of uninterrupted operation at significant brightness (>100 cd m−2) and relatively high power conversion efficiency (2 lm W−1 for orange-red emission). Specifically, by optimizing the composition of the active material and by employing an appropriate operational protocol, a desired doping structure is designed and detrimental chemical and electrochemical side reactions are identified and minimized. Moreover, the first functional flexible LEC with a similar promising device performance is demonstrated.

  • 38.
    Fang, Junfeng
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Matyba, Piotr
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Robinson, Nathaniel D.
    Department of Science and Technology, Linköping University, SE-601 74 Norrköping, Sweden.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Identifying and alleviating electrochemical side-reactions in light-emitting electrochemical cells.2008Inngår i: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 130, s. 4562-4568Artikkel i tidsskrift (Fagfellevurdert)
  • 39.
    Fang, Junfeng
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Yang, Yali
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Understanding the Operation of Light-Emitting Electrochemical Cells.2008Inngår i: Applied Physics Letters, Vol. 93, s. 063503-Artikkel i tidsskrift (Fagfellevurdert)
  • 40. Gerz, Isabelle
    et al.
    Lindh, E. Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Thordarson, Pall
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Kullgren, Jolla
    Mindemark, Jonas
    Oligomer Electrolytes for Light-Emitting Electrochemical Cells: Influence of the End Groups on Ion Coordination, Ion Binding, and Turn-on Kinetics2019Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 11, nr 43, s. 40372-40381Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The electrolyte is an essential constituent of the light-emitting electrochemical cell (LEC), since its operating mechanism is dependent on the redistribution of mobile ions in the active layer. Recent developments of new ion transporters have yielded high-performance devices, but knowledge about the interactions between the ionic species and the ion transporters and the influence of these interactions on the LEC performance is lacking. We therefore present a combined computational and experimental effort that demonstrates that the selection of the end group in a star-branched oligomeric ion transporter based on trimethylolpropane ethoxylate has a paramount influence on the ionic interactions in the electrolyte and thereby also on the performance of the corresponding LECs. With hydroxyl end groups, the the salt is strongly coordinated to the ion transporter, which leads to suppression of ion pairing, but the penalty is a hindered ion release and a slow turn-on for the LEC devices. With methoxy end groups, an intermediate coordination strength is seen together with the formation of contact ion pairs, but the LEC performance is very good with fast turn-on. Using a series of ion transporters with alkyl carbonate end groups, the ion transporter:cation coordination strength is lowered further, but the turn-on kinetics are slower than what is seen for devices comprising the methoxy end-capped ion transporter.

  • 41. Heeger, Alan J
    et al.
    Pauchard-Strebel, Marc
    Vehse, Martin
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Moses, Daniel
    Injection lasers fabricated from semiconducting polymers2004Patent (Annet (populærvitenskap, debatt, mm))
    Abstract [en]

    A solid state lasing structure comprising a field effect transistor in which source and drain electrodes are disposed on a semiconducting light emitting organic polymer forming an active layer on a gate whereby current between the source and drain electrodes defines and flows along a channel in the active layer to define a recombination and emission zone

  • 42.
    Iqbal, Javed
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen. Department of Chemistry, University of Agriculture, Faisalabad 38040, Pakistan.
    Enevold, Jenny
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wang, Jia
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Revoju, Srikanth
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Barzegar, Hamid Reza
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Wågberg, Thomas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Eliasson, Bertil
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Kemiska institutionen.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    An arylene-vinylene based donor-acceptor-donor small molecule for the donor compound in high-voltage organic solar cells2016Inngår i: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 155, s. 348-355Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A donor-acceptor-donor (D-A-D) molecule has been designed and synthesized for use as the electron donating material in solution-processed small-molecule organic solar cells (OSCs). The D-A-D molecule comprises a central electron-accepting (2Z,2'Z)-2,2'-(2,5-bis(octyloxy)-1,4-phenylene)bis(3-(thiophen-2-yl)acry lonitrile) (ZOPTAN) core, which is chemically connected to two peripheral and electron-donating triphenylamine (TPA) units. The ZOPTAN-TPA molecule features a low HOMO level of -5.2 eV and an optical energy gap of 2.1 eV. Champion OSCs based on a solution-processed and non-annealed active material blend of [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM) and ZOPTAN-TPA in a mass ratio of 2:1 exhibits a power conversion efficiency of 1.9% and a high open-circuit voltage of 1.0 V. 

  • 43.
    Iwasiewicz, Agniezka
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Shin, Joon Ho
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Variable Force Tapping AFM Phase Imaging as a Tool in the Characterization of Organic Devices.2006Inngår i: Extended abstracts - Scanning Probe Microscopy, Sensors and Nanostructures, 2006Konferansepaper (Annet (populærvitenskap, debatt, mm))
  • 44.
    Iwasiewicz, Agniezka
    et al.
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Shin, Joon Ho
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Xiao, Steven
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskaplig fakultet, Fysik.
    Variable Force Tapping Atomic Force Microscopy as a Tool in the Characterization of Organic Devices2007Inngår i: Ultramicroscopy, Vol. 107, s. 1078-1085Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    A common method for characterizing the phase separation of materials in mixtures is tapping mode atomic force microscopy (AFM). However, AFM results are influenced by surface-energy effects and the employed tapping force, and it might therefore be difficult to attain correct information regarding the bulk with such a surface imaging technique. In this work, we present a way of imaging material phase separation in an improved manner by recording a series of AFM images at different tapping force. More specifically, we have employed the variable-force AFM method on organic mixtures, comprising a conjugated polymer (MEH-PPV) and an ion-conducting polymer electrolyte (PEO-XCF3SO3, X = Li, K, Rb), and we demonstrate that it is capable of reversibly sampling such materials not only on the surface, but also (indirectly) in the topmost part of the bulk. The analysis of the evolution of AFM phase images allows us to (indirectly) gain information about the bulk phase separation of materials. We find that the variable-force AFM results correlate well with the device performance of light-emitting electrochemical cells employing such organic mixtures as the active material.

  • 45.
    Jin, Xu
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China; School of Mechanical Engineering, Dongguan University of Technology, Dongguan 523808, China.
    Sandström, Andreas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Linnaeus Vag 24, SE-901 87 Umeå, Sweden.
    Lindh, E. Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Yang, Wei
    Tang, Shi
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Linnaeus Vag 24, SE-901 87 Umeå, Sweden.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik. LunaLEC AB, Linnaeus Vag 24, SE-901 87 Umeå, Sweden.
    Challenging conventional wisdom: finding high-performance electrodes for light-emitting electrochemical cells2018Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, nr 39, s. 33380-33389Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The light-emitting electrochemical cell (LEC) exhibits capacity for efficient charge injection from two air stable electrodes into a single-layer active material, which is commonly interpreted as implying that the LEC operation is independent of the electrode selection. Here, we demonstrate that this is far from the truth and that the electrode selection instead has a strong influence on the LEC performance. We systematically investigate 13 different materials for the positive anode and negative cathode in a common LEC configuration with the conjugated polymer Super Yellow as the electroactive emitter and find that Ca, Mn, Ag, Al, Cu, indium tin oxide (ITO), and Au function as the LEC cathode, whereas ITO and Ni can operate as the LEC anode. Importantly, we demonstrate that the electrochemical stability of the electrode is paramount and that particularly electrochemical oxidation of the anode can prohibit the functional LEC operation. We finally report that it appears preferable to design the device so that the heights of the injection barriers at the two electrode/active material interfaces are balanced in order to mitigate electrode-induced quenching of the light emission. As such, this study has expanded the set of air-stable electrode materials available for functional LEC operation and also established a procedure for the evaluation and design of future efficient electrode materials.

  • 46.
    Kaihovirta, Nikolai
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Asadpoordarvish, Amir
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Sandström, Andreas
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Doping-Induced Self-Absorption in Light-Emitting Electrochemical Cells2014Inngår i: ACS Photonics, E-ISSN 2330-4022, Vol. 1, nr 3, s. 182-189Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the quantitative effects of doping-induced self-absorption in light-emitting electrochemical cells (LECs) as a function of active material (AM) thickness and doping concentration. For state-of-the-art polymer LECs with optimized doping concentration and comprising Super Yellow as the electroluminescent (EL) polymer and poly(ethylene oxide)-KCF3SO3 as the electrolyte, we find that the self-absorption loss at the EL peak wavelength is similar to 10% for a 100 nm thin AM and >70% for a 1 mu m thick AM. This implies that the utilization of micrometer-thick AMs fit for fault-tolerant large-scale fabrication can be concomitant with a notable penalty in device performance, and that spatial variations in AM thickness will be manifested in a corresponding spatial light-intensity variation. Moreover, we find that inclusion of a poly(ethylene oxide)-KCF3SO3 electrolyte can inhibit the out-coupling of light and suggest that the culprit is light scattering from dispersed crystalline-electrolyte domains. Finally, we demonstrate evidence for that the selected initial salt concentration in an LEC device dictates the maximum doping concentration that can be attained at steady-state operation.

  • 47.
    Kaihovirta, Nikolai
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Improving the Performance of Light-Emitting Electrochemical Cells by Optical Design2014Inngår i: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, nr 4, s. 2947-2954Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The organic light-emitting electrochemical cell (LEG) has emerged as an enabling technology for a wide range of novel and low-cost emissive applications, but its efficiency is still relatively modest. The focus in the field has so far almost exclusively been directed toward limiting internal loss mechanisms, whereas external losses resulting from poor light-outcoupling have been overlooked. Here, we report a straightforward procedure for improving the efficiency and emission quality of LECs. We find that our high-performance glass-encapsulated LECs exhibit a near-ideal Lambertian emission profile but that total internal reflection at the glass/air interface and a concomitant edge emission and self-absorption represent a significant loss factor. We demonstrate a 60% improvement in the outcoupled luminance in the forward direction by laminating a light-outcoupling film, featuring a hexagonal array of hemispherical microlenses as the surface structure, onto the front side of the device and a large-area metallic reflector onto the back side. With this scalable approach, yellow-emitting LEC devices with a power conversion efficiency of more than 15 lm W-1 at a luminance of 100 cd m(-2) were realized. Importantly, we find that the same procedure also can mitigate problems with spatial variation in the light-emission intensity, which is a common and undesired feature of large-area LECs.

  • 48.
    Kaihovirta, Nikolai
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Longo, Giulia
    Gil-Escrig, Lidon
    Bolink, Henk J.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Self-absorption in a light-emitting electrochemical cell based on an ionic transition metal complex2015Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 106, nr 10, artikkel-id 103502Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the quantitative and qualitative effects of self-absorption in light-emitting electrochemical cells (LECs) based on ionic transition metal complexes (iTMCs), as measured in-situ during electric driving. A yellow-emitting iTMC-LEC comprising an active material thickness of 95 nm suffers a 4% loss of the emission intensity to self-absorption, whereas the same type of device but with a larger active-material thickness of 1 mu m will lose a significant 40% of the light intensity. We also find that the LEC-specific effect of doping-induced self-absorption can result in a drift of the emission spectrum with time for iTMC-LECs, but note that the overall magnitude of doping-induced self-absorption is much smaller than for conjugated-polymer LECs.

  • 49. Keshmiri, V.
    et al.
    Larsen, Christian
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Forchheimer, R.
    Tu, D.
    A Current Supply with Single Organic Thin-Film Transistor for Charging Supercapacitors2016Inngår i: THIN FILM TRANSISTORS 13 (TFT 13) / [ed] Kuo, Y, ELECTROCHEMICAL SOC INC , 2016, Vol. 75, nr 10, s. 217-222Konferansepaper (Fagfellevurdert)
    Abstract [en]

    We present a current supply, comprising a single organic thin-film transistor (OTFT), for the charging of supercapacitors. The current supply takes power from the electric grid (115 V AC, US standard), converts the AC voltage to a quasi-constant DC current (similar to 0.1 mA) regardless of the impedance of the load, and charges the supercapacitor. Solution-processed OTFTs based on the popular polymeric semiconductor poly(3-hexylthiophene- 2,5-diyl) have been developed to rectify the 115 V AC voltage. A diodeconfigured OTFT was used as a half-wave rectifier. The single OTFT current supply was demonstrated to charge a 220 mF supercapacitor to 1 V directly using 115 V AC voltage as the input. This work paves the road towards all-printable supercapacitor energy-storage systems with integrated chargers, which enable direct charging from a power outlet.

  • 50.
    Lanz, Thomas
    et al.
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Lindh, E. Mattias
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    Edman, Ludvig
    Umeå universitet, Teknisk-naturvetenskapliga fakulteten, Institutionen för fysik.
    On the asymmetric evolution of the optical properties of a conjugated polymer during electrochemical p- and n-type doping2017Inngår i: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 5, nr 19, s. 4706-4715Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    We report on the in situ measured evolution of the spectral complex refractive index of a prototypical conjugated polymer, a phenyl-substituted poly (para-phenylenevinylene) copolymer (Ph-PPV, “Super Yellow”), during electrochemical p- and n-type doping. We find that the real part of the refractive index is lowered in a significant and continuous fashion over essentially the entire visible range with doping, as exemplified by a drop in the peak value at ∼480 nm from 2.1 for pristine Ph-PPV to 1.8 at a p-type doping concentration of 0.2 dopants per repeat unit and an n-type doping concentration of 0.6 dopants per repeat unit. The imaginary part features a concomitant distinct bleaching of the high-energy π–π* transition and the emergence of a low-energy polaron band. Interestingly, we observe that the optical response of Ph-PPV to p-type and n-type doping is highly asymmetric, with the former resulting in much stronger changes and a distinct blue-shift of all optical transitions. We tentatively attribute this difference in response to larger effective size of the p-type polaron compared to the n-type polaron. We anticipate that the presented results should be of value for the rational design of emerging optical devices that utilize the doping capacity of conjugated polymers.

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