umu.sePublications
Change search
Refine search result
1 - 22 of 22
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Asadpoordarvish, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC, Umeå, Sweden.
    Sandström, Andreas
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bollström, Roger
    Toivakka, Martti
    Österbacka, Ronald
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Light-Emitting Paper2015In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 25, no 21, p. 3238-3245Article in journal (Refereed)
    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.

  • 2.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hu, Guangzhi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jia, Xueen
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Palladium nanocrystals supported on photo-transformed C-60 nanorods: effect of crystal morphology and electron mobility on the electrocatalytic activity towards ethanol oxidation2014In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 73, p. 34-40Article in journal (Refereed)
    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.

  • 3.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. 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 University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zettl, Alex
    Department of Physics, University of California, Berkeley, California 94720, United States.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Self-assembled PCBM nanosheets: a facile route to electronic layer-on-Layer heterostructures2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 2, p. 1442-1447Article in journal (Refereed)
    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.

  • 4.
    Barzegar, Hamid Reza
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Solution-Based Phototransformation of C-60 Nanorods: Towards Improved Electronic Devices2013In: Particle & particle systems characterization, ISSN 0934-0866, E-ISSN 1521-4117, Vol. 30, no 8, p. 715-720Article in journal (Refereed)
    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.

  • 5.
    Enevold, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zakrisson, Johan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Andersson, Magnus
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Realizing large-area arrays of semiconducting fullerene nanostructures with direct laser interference patterning2018In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 18, no 1, p. 540-545Article in journal (Refereed)
  • 6.
    Iqbal, Javed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry. Department of Chemistry, University of Agriculture, Faisalabad 38040, Pakistan.
    Enevold, Jenny
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Revoju, Srikanth
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Barzegar, Hamid Reza
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bertil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    An arylene-vinylene based donor-acceptor-donor small molecule for the donor compound in high-voltage organic solar cells2016In: Solar Energy Materials and Solar Cells, ISSN 0927-0248, E-ISSN 1879-3398, Vol. 155, p. 348-355Article in journal (Refereed)
    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. 

  • 7.
    Iqbal, Javed
    et al.
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Enevold, Jenny
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Eliasson, Bertil
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    An Arylene-Vinylene Based Donor-Acceptor-Donor Small Molecule for the DonorCompound in High-Voltage Organic Solar CellsArticle in journal (Other academic)
    Abstract [en]

    ne"> 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)acrylonitrile) (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-C61-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.

  • 8.
    Kaihovirta, Nikolai
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Improving the Performance of Light-Emitting Electrochemical Cells by Optical Design2014In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 6, no 4, p. 2947-2954Article in journal (Refereed)
    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.

  • 9. Keshmiri, V.
    et al.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forchheimer, R.
    Tu, D.
    A Current Supply with Single Organic Thin-Film Transistor for Charging Supercapacitors2016In: THIN FILM TRANSISTORS 13 (TFT 13) / [ed] Kuo, Y, ELECTROCHEMICAL SOC INC , 2016, Vol. 75, no 10, p. 217-222Conference paper (Refereed)
    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.

  • 10.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fabricating designed fullerene nanostructures for functional electronic devices2014Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    A long-term goal within the field of organic electronics has been to developflexible and functional devices, which can be processed and patterned withlow-cost and energy-efficient solution-based methods. This thesis presents anumber of functional paths towards the attainment of this goal via thedevelopment and demonstration of novel fabrication and patterningmethods involving the important organic-semiconductor family termedfullerenes.Fullerenes are soccer-shaped small molecules, with two often-employedexamples being the symmetric C60 molecule and its more soluble derivative[6,6]-phenyl-C61-butyric acid methyl ester (PCBM). We show that PCBM canbe photochemically transformed into a dimeric state in a bi-excited reactionprocess, and that the exposed material features a significantly reducedsolubility in common solvents as well as an effectively retained electronmobility. This attractive combination of material properties allows for adirect and resist-free lithographic patterning of electronic PCBM films downto a smallest feature size of 1 µm, using a simple and scalable two-stepprocess constituting light exposure and solution development. In a furtherdevelopment, it was shown that the two-step method was useful also in thearea-selective transformation of fullerene/conjugated-polymer blend films,as demonstrated through the realization of a functional complementary logiccircuit comprising a 5-stage ring oscillator.In another project, we have synthesized highly flexible, single-crystal C60nanorods with a solution-based self-assembly process termed liquid-liquidinterfacial precipitation. The 1-dimensional nanorods can be deposited fromtheir synthesis solution and employed as the active material in field-effecttransistor devices. Here, it was revealed that the as-fabricated nanorods canfeature an impressive electron mobility of 1.0 cm2 V-1 s-1, which is on par withthe performance of a work horse in the transistor field, viz. vacuumdeposited amorphous Si. We further demonstrated that the processability ofthe nanorods can be improved by a tuned light-exposure treatment, duringwhich the nanorod shell is polymerized while the high-mobility interior bulkis left intact. This has the desired consequence that stabile nanoroddispersions can be prepared in a wide range of solvents, and we anticipatethat functional electronic devices based on solution-processable nanorodscan be realized in a near future.

  • 11.
    Larsen, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Barzegar, Hamid Reza
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Nitze, Florian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On the fabrication of crystalline C-60 nanorod transistors from solution2012In: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 23, no 34, p. 344015-Article in journal (Refereed)
    Abstract [en]

    Flexible and high-aspect-ratio C-60 nanorods are synthesized using a liquid-liquid interfacial precipitation process. As-grown nanorods are shown to exhibit a hexagonal close-packed single-crystal structure, with m-dichlorobenzene solvent molecules incorporated into the crystalline structure in a C-60:m-dichlorobenzene ratio of 3.2. An annealing step at 200 degrees C transforms the nanorods into a solvent-free face-centred-cubic polycrystalline structure. The nanorods are deposited onto field-effect transistor structures using two solvent-based techniques: drop-casting and dip-coating. We find that dip-coating deposition results in a preferred alignment of non-bundled nanorods and a satisfying transistor performance. The latter is quantified by the attainment of an electron mobility of 0.08 cm(2) V-1 s(-1) and an on/off ratio of >10(4) for a single-crystal nanorod transistor, fabricated with a solution-based and low-temperature process that is compatible with flexible substrates.

  • 12.
    Larsen, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forchheimer, Robert
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tu, Deyu
    Design, fabrication and application of organic power converters: Driving light-emitting electrochemical cells from the AC mains2017In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 45, p. 57-64Article in journal (Refereed)
    Abstract [en]

    The design, fabrication and operation of a range of functional power converter circuits, based on diode configured organic field-effect transistors as the rectifying unit and capable of transforming a high AC input voltage to a selectable DC voltage, are presented. The converter functionality is demonstrated by selecting and tuning its constituents so that it can effectively drive a low-voltage organic electronic device, a light-emitting electrochemical cell (LEC), when connected to high-voltage AC mains. It is established that the preferred converter circuit for this task comprises an organic full-wave rectifier and a regulation resistor but is void of a smoothing capacitor, and that such a circuit connected to the AC mains (230 V, 50 Hz) successfully can drive an LEC to bright luminance (360 cd m(-2)) and high efficiency (6.4 cd A(-1)).

  • 13.
    Larsen, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Complementary ring oscillator fabricated via direct laser-exposure and solution-processing of a single-layer organic film2012In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 520, no 7, p. 3009-3012Article in journal (Refereed)
    Abstract [en]

    A complementary ring oscillator is realized by exposing a solution-processed single-layer organic film to area-selective laser-light exposure and solution development. The pristine film comprises a blend of two organic semiconductors: p-type poly(3-hexylthiophene-2,5-diyl) (P3HT) and n-type [6,6]-phenyl C-61 butyric acid methyl ester (PCBM). The exposure transforms PCBM into an insoluble form, and the subsequent development selectively removes the non-exposed PCBM while leaving exposed PCBM and P3HT intact. The 5-step ring oscillator exhibits a frequency of 10 mHz, a power delay product of 2.0 mu J, and an energy delay product of 22 mu Js. Opportunities for performance improvements of the scalable fabrication technique are highlighted in an accompanying analysis.

  • 14. Murto, Petri
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, SE-90187 Umeå, Sweden.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, SE-90187 Umeå, Sweden.
    Xu, Xiaofeng
    Sandström, Andreas
    Pietarinen, Juuso
    Bagemihl, Benedikt
    Abdulahi, Birhan A.
    Mammo, Wendimagegn
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, SE-90187 Umeå, Sweden.
    Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell2018In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 4, p. 1753-1761Article in journal (Refereed)
    Abstract [en]

    Cost-efficient thin-film devices that emit in the near-infrared (NIR) range promise a wide range of important applications. Here, the synthesis and NIR application of a series of copolymers comprising poly[indacenodithieno[3,2-b]thiophene-2,8-diyl] (PIDTT) as the host and different donor–acceptor–donor (DAD) segments as the guest are reported. We find that a key design criterion for efficient solid-state host-to-guest energy transfer is that the DAD conformation is compatible with the conformation of the host. Such host–guest copolymers are evaluated as the emitter in light-emitting electrochemical cells (LECs) and organic light-emitting diodes, and the best performance is invariably attained from the LEC devices because of the observed balanced electrochemical doping that alleviates issues with a noncentered emission zone. An LEC device comprising a host–guest copolymer with 4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b′]dithiophene as the donor and benzo[c][1,2,5]thiadiazole as the acceptor delivers an impressive near-infrared (NIR) performance in the form of a high radiance of 1458 μW/cm2 at a peak wavelength of 725 nm when driven by a current density of 500 mA/cm2, a second-fast turn-on, and a good stress stability as manifested in a constant radiance output during 3 days of uninterrupted operation. The high-molecular-weight copolymer features excellent processability, and the potential for low-cost and scalable NIR applications is verified through a spray-coating fabrication of a >40 cm2 large-area device, which emits intense and uniform NIR light at a low drive voltage of 4.5 V.

  • 15. Murto, Petri
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, Umeå, Sweden.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, Umeå, Sweden.
    Xu, Xiaofeng
    Sandström, Andreas
    LunaLEC AB, Umeå University, Umeå, Sweden.
    Pietarinen, Juuso
    Bagemihl, Benedikt
    Abdulahi, Birhan A.
    Mammo, Wendimagegn
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå University, Umeå, Sweden.
    Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell2018In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 4, p. 1753-1761Article in journal (Refereed)
    Abstract [en]

    Cost-efficient thin-film devices that emit in the near infrared (NIR) range promise a wide range of important applications. Here, the synthesis and NIR application of a series of copolymers comprising poly[indacenodithieno[3,2-b]thiophene-2,8-diyl] (PIDTT) as the host and different donor acceptor donor (DAD) segments as the guest are reported. We find that a key design criterion for efficient solid-state host-to-guest energy transfer is that the DAD conformation is compatible with the conformation of the host. Such host guest copolymers are evaluated as the emitter in light-emitting electrochemical cells (LECs) and organic light-emitting diodes, and the best performance is invariably attained from the LEC devices because of the observed balanced electrochemical doping that alleviates issues with a noncentered emission zone. An LEC device comprising a host guest copolymer with 4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b']dithiophene as the donor and benzo[c][1,2,5]thiadiazole as the acceptor delivers an impressive near-infrared (NIR) performance in the form of a high radiance of 1458 mu W/cm(2) at a peak wavelength of 725 nm when driven by a current density of 500 mA/cm(2), a second-fast turn-on, and a good stress stability as manifested in a constant radiance output during 3 days of uninterrupted operation. The high-molecular-weight copolymer features excellent processability, and the potential for low-cost and scalable NIR applications is verified through a spray-coating fabrication of a >40 cm(2) large-area device, which emits intense and uniform NIR light at a low drive voltage of 4.5 V.

  • 16.
    Sharifi, Tiva
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kwong, Wai Ling
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Berends, Hans-Martin
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Maghemite nanorods anchored on a 3D nitrogen-doped carbon nanotubes substrate as scalable direct electrode for water oxidation2016In: International journal of hydrogen energy, ISSN 0360-3199, E-ISSN 1879-3487, Vol. 41, no 1, p. 69-78Article in journal (Refereed)
    Abstract [en]

    A hybrid catalyst 3D electrode for electrochemical water oxidation to molecular oxygen is presented. The electrode comprises needle shaped maghemite nanorods firmly anchored to nitrogen doped carbon nanotubes, which in turn are grown on a conducting carbon paper that acts as efficient current collector. In 0.1 M KOH this hybrid electrode reaches a current density of 1 mA/cm(2) (geometric surface) at an overpotential of 362 mV performing high chronoamperometric stability. The electrochemical attributes point toward efficient catalytic processes at the surface of the maghemite nanorods, and demonstrate a very high surface area of the 3D electrode, as well as a firm anchoring of each active component enabling an efficient charge transport from the surface of the maghemite rods to the carbon paper current collector. The latter property also explains the good stability of our hybrid electrode compared to transition metal oxides deposited on conducting support such as fluorine doped tin oxide. These results introduce maghemite as efficient, stable and earth abundant oxygen evolution reaction catalyst, and provide insight into key issues for obtaining practical electrodes for oxygen evolution reaction, which are compatible with large scale production processes. 

  • 17.
    Sharifi, Tiva
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kwong, Wai Ling
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mercier, Guillaume
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Messinger, Johannes
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Toward a Low-Cost Artificial Leaf: Driving Carbon-Based and Bifunctional Catalyst Electrodes with Solution-Processed Perovskite Photovoltaics2016In: Advanced Energy Materials, ISSN 1614-6832, Vol. 6, no 20, p. 1-10, article id 1600738Article in journal (Refereed)
    Abstract [en]

    Molecular hydrogen can be generated renewably by water splitting with an artificial-leaf device, which essentially comprises two electrocatalyst electrodes immersed in water and powered by photovoltaics. Ideally, this device should operate efficiently and be fabricated with cost-efficient means using earth-abundant materials. Here, a lightweight electrocatalyst electrode, comprising large surface-area NiCo2O4 nanorods that are firmly anchored onto a carbon-paper current collector via a dense network of nitrogen-doped carbon nanotubes is presented. This electrocatalyst electrode is bifunctional in that it can efficiently operate as both anode and cathode in the same alkaline solution, as quantified by a delivered current density of 10 mA cm(-2) at an overpotential of 400 mV for each of the oxygen and hydrogen evolution reactions. By driving two such identical electrodes with a solution-processed thin-film perovskite photovoltaic assembly, a wired artificial-leaf device is obtained that features a Faradaic H-2 evolution efficiency of 100%, and a solar-to-hydrogen conversion efficiency of 6.2%. A detailed cost analysis is presented, which implies that the material-payback time of this device is of the order of 100 days.

  • 18.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Murto, Petri
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    On the Design of Host-Guest Light-Emitting Electrochemical Cells: Should the Guest be Physically Blended or Chemically Incorporated into the Host for Efficient Emission?2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 18, article id 1900451Article in journal (Refereed)
    Abstract [en]

    It has recently been demonstrated that light‐emitting electrochemical cells (LECs) can be designed to deliver strong emission with high efficiency when the charge transport is effectuated by a majority host and the emission is executed by a minority guest. A relevant question is then: should the guest be physically blended with or chemically incorporated into the host? A systematic study is presented that establishes that for near‐infrared‐(NIR‐) emitting LECs based on poly(indacenodithieno[3,2‐b]thiophene) (PIDTT) as the host and 4,7‐bis(4,4‐bis(2‐ethylhexyl)‐4H‐silolo[3,2‐b:4,5‐b′]dithiophen‐2‐yl)benzo[c][1,2,5]‐thiadiazole (SBS) as the guest the chemical‐incorporation approach is preferable. The host‐to‐guest energy transfer in LEC devices is highly efficient at a low guest concentration of 0.5%, whereas guest aggregation and ion redistribution during device operation severly inhibits this transfer in the physical‐blend devices. The chemical‐incorporation approach also results in a redshifted emission with a somewhat lowered photoluminescence quantum yield, but the LEC performance is nevertheless very good. Specifically, an NIR‐LEC device comprising a guest‐dilute (0.5 molar%) PIDTT‐SBS copolymer delivers highly stabile operation at a high radiance of 263 µW cm−2 (peak wavelength = 725 nm) and with an external quantum efficiency of 0.214%, which is close to the theoretical limit for this particular emitter and device geometry.

  • 19.
    Tang, Shi
    et al.
    The Organic Photonics and Electronics Group, Umeå University: LunaLEC AB, Umeå University, Umeå, Sweden Umeå, Sweden Umeå, Sweden.
    Murto, Petri
    Wang, Jia
    The Organic Photonics and Electronics Group, Umeå University, Umeå, Sweden.
    Larsen, Christian
    The Organic Photonics and Electronics Group, Umeå University; LunaLEC AB, Umeå University, Umeå, Sweden Umeå, Sweden Umeå, Sweden.
    Andersson, Mats R.
    Wang, Ergang
    Edman, Ludvig
    The Organic Photonics and Electronics Group, Umeå University; LunaLEC AB, Umeå University, Umeå, Sweden Umeå, Sweden.
    On the Design of Host-Guest Light-Emitting Electrochemical Cells: Should the Guest be Physically Blended or Chemically Incorporated into the Host for Efficient Emission?2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 18, article id 1900451Article in journal (Refereed)
    Abstract [en]

    It has recently been demonstrated that light-emitting electrochemical cells (LECs) can be designed to deliver strong emission with high efficiency when the charge transport is effectuated by a majority host and the emission is executed by a minority guest. A relevant question is then: should the guest be physically blended with or chemically incorporated into the host? A systematic study is presented that establishes that for near-infrared-(NIR-) emitting LECs based on poly(indacenodithieno[3,2-b]thiophene) (PIDTT) as the host and 4,7-bis(4,4-bis(2-ethylhexyl)-4H-silolo[3,2-b:4,5-b ']dithiophen-2-yl)benzo[c][1,2,5]-thiadiazole (SBS) as the guest the chemical-incorporation approach is preferable. The host-to-guest energy transfer in LEC devices is highly efficient at a low guest concentration of 0.5%, whereas guest aggregation and ion redistribution during device operation severly inhibits this transfer in the physical-blend devices. The chemical-incorporation approach also results in a redshifted emission with a somewhat lowered photoluminescence quantum yield, but the LEC performance is nevertheless very good. Specifically, an NIR-LEC device comprising a guest-dilute (0.5 molar%) PIDTT-SBS copolymer delivers highly stabile operation at a high radiance of 263 mu W cm(-2) (peak wavelength = 725 nm) and with an external quantum efficiency of 0.214%, which is close to the theoretical limit for this particular emitter and device geometry.

  • 20.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Murto, Petri
    Xu, Xiaofeng
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Wang, Ergang
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevagen 47, SE-90719 Umea, Sweden.
    Intense and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells Comprising a Metal-Free Indacenodithieno[3,2-b]thiophene-Based Copolymer as the Single Emitter2017In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 18, p. 7750-7759Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis, characterization, and application of a series of metal-free near-infrared (NIR) emitting alternating donor/acceptor copolymers based on indacenodithieno[3,2-b]thiophene (IDTT) as the donor unit. A light-emitting electrochemical cell (LEC), comprising a blend of the copolymer poly[indacenodithieno[3,2-b]thiophene-2,8-diyl-alt-2,3-diphenyl-5,8-di(thiophen-2-y1)- quinoxaline-5,5'-diy1] and an ionic liquid as the single-layer active material sandwiched between two air-stable electrodes, delivered NIR emission (lambda(peak) = 705 nm) with a high radiance of 129 mu W/cm(2) when driven by a low voltage of 3.4 V. The NIR-LEC also featured good stress stability, as manifested in that the peak NIR output from a nonencapsulated device after 24 h of continuous operation only had dropped by 3% under N-2 atmosphere and by 27% under ambient air. This work accordingly introduces IDTT-based donor/acceptor copolymers as functional metal-free electroluminescent materials in NIR-emitting devices and also provides guidelines for how future NIR emitters should be designed for further improved performance.

  • 21.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Lundberg, Petter
    Lanz, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    LunaLEC AB.
    van Reenen, Stephan
    Kemerink, Martijn
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB.
    Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency2017In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 1190Article in journal (Refereed)
    Abstract [en]

    The light-emitting electrochemical cell promises cost-efficient, large-area emissive applications, as its characteristic in-situ doping enables use of air-stabile electrodes and a solution-processed single-layer active material. However, mutual exclusion of high efficiency and high brightness has proven a seemingly fundamental problem. Here we present a generic approach that overcomes this critical issue, and report on devices equipped with air-stabile electrodes and outcoupling structure that deliver a record-high efficiency of 99.2 cd A(-1) at a bright luminance of 1910 cd m(-2). This device significantly outperforms the corresponding optimized organic light-emitting diode despite the latter employing calcium as the cathode. The key to this achievement is the design of the host-guest active material, in which tailored traps suppress exciton diffusion and quenching in the central recombination zone, allowing efficient triplet emission. Simultaneously, the traps do not significantly hamper electron and hole transport, as essentially all traps in the transport regions are filled by doping.

  • 22.
    Wang, Jia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Direct UV patterning of electronically active fullerene films2011In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 21, no 19, p. 3723-3728Article in journal (Refereed)
    Abstract [en]

    We utilize UV light for the attainment of high-resolution, electronically active patterns in [6,6]-phenyl C61-butyric acid methyl ester (PCBM) films. The patterns are created by directly exposing selected parts of a solution-cast PCBM film to UV light, and thereafter developing the film by immersing it in a tuned developer solution. We demonstrate that it is possible to attain complex, large-area PCBM structures with a smallest demonstrated-feature size of 1 μm by this method, and that the patterned PCBM material exhibits a high average electron mobility (1.2 × 10−2 cm2 V−1 s−1) in transistor experiments. The employment of UV light for direct patterning of PCBM for electronic applications is attractive, because PCBM exhibits high absorption in the UV range, and no sacrificial photoresist is needed. The patterning is achieved through the transformation by UV light of the soluble PCBM monomers into insoluble dimers with retained attractive electronic properties.

1 - 22 of 22
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf