Umeå University's logo

umu.sePublications
Change search
Refine search result
1 - 49 of 49
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.
    Adranno, Brando
    et al.
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
    Renier, Olivier
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
    Bousrez, Guillaume
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
    Paterlini, Veronica
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
    Baryshnikov, Glib V.
    Department of Science and Technology, Laboratory of Organic Electronics, Linköping University, SE-60174 Norrköping, Sweden.
    Smetana, Volodymyr
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ågren, Hans
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Metlen, Andreas
    The QUILL Research Centre and School of Chemistry and Chemical Engineering The Queen’s University of Belfast Belfast, Northern Ireland BT9 5AG, UK.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Anja-Verena, Mudring
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Rogers, Robin D.
    Department of Materials and Environmental Chemistry, Stockholm University, Svante Arrhenius väg 16C, SE-10691 Stockholm, Sweden; The QUILL Research Centre and School of Chemistry and Chemical Engineering The Queen’s University of Belfast Belfast, Northern Ireland BT9 5AG, UK.
    The 8-hydroxyquinolinium cation as a lead structure for efficient color-tunable ionic small molecule emitting materials2023In: Advanced Photonics Research, ISSN 2699-9293, Vol. 4, no 3, article id 2200279Article in journal (Refereed)
    Abstract [en]

    Albeit tris(8-hydroxyquinolinato) aluminum (Alq3) and its derivatives are prominent emitter materials for organic lighting devices, and the optical transitions occur among ligand-centered states, the use of metal-free 8-hydroxyquinoline is impractical as it suffers from strong nonradiative quenching, mainly through fast proton transfer. Herein, it is shown that the problem of rapid proton exchange and vibration quenching of light emission can be overcome not only by complexation, but also by organization of the 8-hydroxyquinolinium cations into a solid rigid network with appropriate counter-anions (here bis(trifluoromethanesulfonyl)imide). The resulting structure is stiffened by secondary bonding interactions such as pi-stacking and hydrogen bonds, which efficiently block rapid proton transfer quenching and reduce vibrational deactivation. Additionally, the optical properties are tuned through methyl substitution from deep blue (455 nm) to blue-green (488 nm). Time-dependent density functional theory (TDFT) calculations reveal the emission to occur from which an unexpectedly long-lived S-1 level, unusual for organic fluorophores. All compounds show comparable, even superior photoluminescence compared to Alq3 and related materials, both as solids and thin films with quantum yields (QYs) up to 40-50%. In addition, all compounds show appreciable thermal stability with decomposition temperatures above 310 °C.

    Download full text (pdf)
    fulltext
  • 2.
    Adranno, Brando
    et al.
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Paterlini, Veronica
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Smetana, Volodymyr
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Renier, Olivier
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden.
    Bousrez, Guillaume
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mudring, Anja-Verena
    Physical Materials Chemistry, Department of Materials and Environmental Chemistry, Stockholm University, 10691 Stockholm, Sweden; Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, 8000 Aarhus C, Denmark.
    Broadband white-light-emitting electrochemical cells2023In: Advanced Photonics Research, ISSN 2699-9293, Vol. 4, no 5, article id 2200351Article in journal (Refereed)
    Abstract [en]

    Emerging organic light-emitting devices, such as light-emitting electrochemical cells (LECs), offer a multitude of advantages but currently suffer from that most efficient phosphorescent emitters are based on expensive and rare metals. Herein, it is demonstrated that a rare metal-free salt, bis(benzyltriphenylphosphonium)tetrabromidomanganate(II) ([Ph3PBn]2[MnBr4]), can function as the phosphorescent emitter in an LEC, and that a careful device design results in the fact that such a rare metal-free phosphorescent LEC delivers broadband white emission with a high color rendering index (CRI) of 89. It is further shown that broadband emission is effectuated by an electric-field-driven structural transformation of the original green-light emitter structure into a red-emitting structure.

    Download full text (pdf)
    fulltext
  • 3.
    Asadpoordarvish, Amir
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Granström, Jimmy
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Encapsulating light-emitting electrochemical cells for improved performance2012In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, article id 193508Article in journal (Refereed)
    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.
    dos Santos, John Marques
    et al.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Chan, Chin-Yiu
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka 744, Fukuoka, Nishi-ku, Japan.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hall, David
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom; Laboratory for Computational Modeling of Functional Materials, Namur Institute of Structured Matter, University of Namur, 61 Rue de Bruxelles, Namur, Belgium.
    Matulaitis, Tomas
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Cordes, David B.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Slawin, Alexandra M. Z.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Tsuchiya, Youichi
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka 744, Fukuoka, Nishi-ku, Japan.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Adachi, Chihaya
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka 744, Fukuoka, Nishi-ku, Japan.
    Olivier, Yoann
    Laboratory for Computational Modeling of Functional Materials, Namur Institute of Structured Matter, University of Namur, 61 Rue de Bruxelles, Namur, Belgium.
    Zysman-Colman, Eli
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Color tuning of multi-resonant thermally activated delayed fluorescence emitters based on fully fused polycyclic amine/carbonyl frameworks2023In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 11, no 24, p. 8263-8273Article in journal (Refereed)
    Abstract [en]

    Two novel π-extended amine/carbonyl-based multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters have been designed and synthesized. The two emitters are isomeric, composed of nine fused rings and show green-yellow emission. Sym-DiDiKTa and Asym-DiDiKTa possess tert-butyl groups distributed in a symmetrical and asymmetrical fashion, respectively, which significantly impact the single-crystal packing structure. The two compounds possess similar singlet-triplet energy gaps, ΔEST, of around 0.23 eV, narrowband emission characterized by a full-width at half-maximum, FWHM, of 29 nm and a photoluminescence quantum yield, ΦPL, of 70% and 53% for the symmetric and asymmetric counterparts, respectively, in toluene. Investigation in OLEDs demonstrated that the devices with Sym-DiDiKTa and Asym-DiDiKTa displayed electroluminescence maxima of 543 and 544 nm, and maximum external quantum efficiencies (EQEmax) of 9.8% and 10.5%, respectively. The maximum EQE was further improved to 19.9% by employing a hyperfluorescence strategy. We further present the first example of a neutral MR-TADF emitter incorporated in a LEC device where Sym-DiDiKTa acts as the emitter. The LEC shows a λEL at 551 nm and FWHM of 60 nm with luminance of 300 cd m−2 and a fast turn-on time of less than 2 s to 100 cd m−2

    Download full text (pdf)
    fulltext
  • 5.
    Edman, Ludvig
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On-demand photochemical stabilization of doping in light-emitting electrochemical cells2011In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 56, no 28, p. 10473-10478Article in journal (Refereed)
    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.

    Download full text (pdf)
    fulltext
  • 6.
    Enevold, Jenny
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dahlberg, Tobias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Stangner, Tim
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lindh, E. Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    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.
    Tunable two-dimensional patterning of a semiconducting Nanometer-Thin C60 fullerene film using a spatial light modulator2020In: ACS Applied Nano Materials, ISSN 2574-0970, Vol. 3, no 6, p. 2574-0970Article in journal (Other academic)
    Abstract [en]

    The photochemical coupling of fullerene molecules into covalently connected oligomeric or polymeric structures can result in drastically lowered solubility in common solvents with retained semiconductor properties. Here, we exploit this combination of properties for the utilization of fullerenes as a negative photoresist material with electronic functionality. Specifically, we develop an easily tunable exposure system, essentially comprising a laser and a computer-controlled spatial light modulator (SLM) featuring >8 million independently controlled pixels, for the spatially selective photochemical transformation of nanometer-thin C60 fullerene films. With a carefully designed laser-SLM-exposure/solvent-development cycle, we are able to realize well-resolved two-dimensional hexagonal or square patterns of circular C60 microdots with a center-to-center distance of 1–5 μm and a maximum thickness of 20–35 nm over several square-millimeter-sized areas on a substrate. The functionality of such a hexagonal C60 pattern was demonstrated by its inclusion in between the transparent electrode and the active material in a light-emitting electrochemical cell, which featured an enhanced light output by >50% in comparison to a reference device void of the patterned C60 layer.

    Download full text (pdf)
    fulltext
  • 7.
    Filate, Tadele T.
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden; Department of Chemistry, Addis Ababa University, PO Box 33658, Addis Ababa, Ethiopia.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Genene, Zewdneh
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mammo, Wendimagegn
    Department of Chemistry, Addis Ababa University, PO Box 33658, Addis Ababa, Ethiopia.
    Wang, Ergang
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Hydrophilic conjugated polymers for sustainable fabrication of deep-red light-emitting electrochemical cells2024In: Advanced Materials Technologies, E-ISSN 2365-709X, Vol. 9, no 3, article id 2301696Article in journal (Refereed)
    Abstract [en]

    It is crucial to develop functional electronic materials that can be processed from green solvents to achieve environmentally sustainable and cost-efficient printing fabrication of organic electronic devices. Here, the design and cost-efficient synthesis of two hydrophilic and emissive conjugated polymers, TQ-OEG and TQ2F-OEG, are presented, which are rendered hydrophilic through the grafting of oligo(ethylene glycol) (OEG) solubilizing groups onto the thiophene-quinoxaline conjugated backbone and thereby can be processed from a water:ethanol solvent mixture. It is shown that the introduction of the OEG groups enables for a direct dissolution of salts by the neat polymer for the attainment of solid-state ion mobility. These properties are utilized for the design and development of light-emitting electrochemical cells (LECs), the active materials of which can be solution cast from a water:ethanol-based ink. It is specifically shown that such an LEC device, comprising an optimized blend of the TQ2F-OEG emitter and a Li salt as the active material positioned between two air-stabile electrodes, delivers deep-red emission (peak wavelength = 670 nm) with a radiance of 185 µW m−2 at a low drive voltage of 2.3 V. This study contributes relevant information as to how polymers and LEC devices can be designed and fabricated to combine functionality with sustainability.

    Download full text (pdf)
    fulltext
  • 8.
    Huseynova, Gunel
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Auroux, Etienne
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Huang, Ping
    Department of Chemistry, Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Tang, Shi
    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.
    Chemical doping to control the in-situ formed doping structure in light-emitting electrochemical cells2023In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 11457Article in journal (Refereed)
    Abstract [en]

    The initial operation of a light-emitting electrochemical cell (LEC) constitutes the in-situ formation of a p-n junction doping structure in the active material by electrochemical doping. It has been firmly established that the spatial position of the emissive p-n junction in the interelectrode gap has a profound influence on the LEC performance because of exciton quenching and microcavity effects. Hence, practical strategies for a control of the position of the p-n junction in LEC devices are highly desired. Here, we introduce a "chemical pre-doping" approach for the rational shifting of the p-n junction for improved performance. Specifically, we demonstrate, by combined experiments and simulations, that the addition of a strong chemical reductant termed "reduced benzyl viologen" to a common active-material ink during LEC fabrication results in a filling of deep electron traps and an associated shifting of the emissive p-n junction from the center of the active material towards the positive anode. We finally demonstrate that this chemical pre-doping approach can improve the emission efficiency and stability of a common LEC device.

    Download full text (pdf)
    fulltext
  • 9.
    Jin, Xu
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. 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 University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Linnaeus Vag 24, SE-901 87 Umeå, Sweden.
    Lindh, E. Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yang, Wei
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Linnaeus Vag 24, SE-901 87 Umeå, Sweden.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Linnaeus Vag 24, SE-901 87 Umeå, Sweden.
    Challenging conventional wisdom: finding high-performance electrodes for light-emitting electrochemical cells2018In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 39, p. 33380-33389Article in journal (Refereed)
    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.

  • 10.
    Kotewicz, Krzysztof
    et al.
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Ergang
    Department of Chemistry and Chemical Engineering, Chalmers University of Technology, Göteborg, Sweden.
    Mild and efficient extraction of fluorescent chlorophyll a from spinach leaves for application as the sustainable emitter in light-emitting electrochemical cells2024In: ChemElectroChem, E-ISSN 2196-0216, Vol. 11, no 5, article id e202300629Article in journal (Refereed)
    Abstract [en]

    Natural pigments are sustainable compounds that can be employed as emitters, sensors and sensitisers in optoelectronics. The most abundant pigment, chlorophyll, offers advantages of easily available and plentiful feedstock, biodegradability and non-toxicity. However, strenuous extraction and separation limit its application on larger scale. In this work, a practically mild and scalable extraction and separation method for rapid isolation of chlorophyll a from spinach is presented. Three different stationary phases for column chromatography were evaluated, and a new solvent system was developed for the elution of chlorophyll a on a neutral alumina chromatography column. The purified product was obtained with a yield of 0.98 mg ⋅ g−1 with respect to the dry leaves. A first light-emitting electrochemical cell (LEC) based on chlorophyll a as the emitter is reported, using the extracted chlorophyll a as the guest compound dispersed in a blend-host matrix in a concentration of 2.5 or 5 mass %. The higher-chlorophyll-concentration LEC exhibits emission solely from the chlorophyll emitter, with the main emission peak located at 675 nm. The lower-chlorophyll-concentration LEC features two distinct emission bands, one in the red region that is originating from the chlorophyll guest and one in the blue region (main peak at 430 nm) that stems from the blend host. This combined red:blue emission can be attractive for, e. g., greenhouse applications, since it matches the action spectrum of plant photosynthesis.

    Download full text (pdf)
    fulltext
  • 11.
    Lanz, Thomas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    Chabrecek, Peter
    Sefar AG.
    Sonderegger, Uriel
    Sefar AG.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Tvistevägen 47, PO Box 7970, SE-90719 Umeå, Sweden.
    A light–emission textile device: conformal spray-sintering of a woven fabric electrode2016In: Flexible and Printed Electronics, ISSN 2058-8585, Vol. 1, no 2, article id 025004Article in journal (Refereed)
    Abstract [en]

    We report on the realization of an ultra-flexible, light-weight and large-area emissive textile device. The anode and active material of a light-emitting electrochemical cell (LEC) were deposited by conformal spray-coating of a transparent fabric-based electrode, comprising a weave of fine Ag-coated Cu wires and poly(ethylene naphthalene) monofilament fibers embedded in a polyurethane matrix. The yellow-emitting textile featured low turn-on voltage (5 V), high maximum brightness (>4000 cd m−2), good efficiency (3.4 cd A−1), and reasonable lifetime (180 h at >100 cd m−2). Uniform emission to the eye was attained from thin and highly flexible textiles featuring a large emission area of 42 cm2, without resorting to planarization of the partially wavy-shaped (valley-to-peak height = 2.7 μm) fabric electrode. The key enabling factors for the functional emissive textile are the characteristic in situ electrochemical doping of LEC devices, the 'dry' spray-sintering deposition of the active material, and the attractive mechanical, electronic and optical properties of the fabric-based electrode.

  • 12.
    Larsen, Christian
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Lundberg, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Lindh, E. Mattias
    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. LunaLEC AB, Umeå, Sweden.
    A tool for identifying green solvents for printed electronics2021In: Nature Communications, E-ISSN 2041-1723, Vol. 12, article id 4510Article in journal (Refereed)
    Abstract [en]

    The emerging field of printed electronics uses large amounts of printing and coating solvents during fabrication, which commonly are deposited and evaporated within spaces available to workers. It is in this context unfortunate that many of the currently employed solvents are non-desirable from health, safety, or environmental perspectives. Here, we address this issue through the development of a tool for the straightforward identification of functional and "green" replacement solvents. In short, the tool organizes a large set of solvents according to their Hansen solubility parameters, ink properties, and sustainability descriptors, and through systematic iteration delivers suggestions for green alternative solvents with similar dissolution capacity as the current non-sustainable solvent. We exemplify the merit of the tool in a case study on a multi-solute ink for high-performance light-emitting electrochemical cells, where a non-desired solvent was successfully replaced by two benign alternatives. The green-solvent selection tool is freely available at: www.opeg-umu.se/green-solvent-tool.

    Download full text (pdf)
    fulltext
  • 13.
    Liu, Yong-feng
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fan, Junpeng
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Yang, Jinpeng
    College of Physical Science and Technology, Yangzhou University, Jiangsu 225009, China.
    Liu, Xianjie
    Kera, Satoshi
    Department of Photo-Molecular Science, Institute for Molecular Science, Myodaiji, Okazaki 444-8585, Japan; .
    Fahlman, Mats
    Laboratory for Organic Electronics, ITN, Linköping University, Norrköping SE-60174, Sweden.
    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.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Highly Soluble CsPbBr3 Perovskite Quantum Dots for Solution-Processed Light-Emission Devices2021In: ACS Applied Nano Materials, E-ISSN 2574-0970, p. 1162-1174Article in journal (Refereed)
    Abstract [en]

    We report on the synthesis of CsPbBr3 perovskite quantum dots (PeQDs) with a high solubility of 75 g/L in toluene and a good film-forming property, as enabled by a dense layer of didodecyldimethylammonium bromide and octanoic acid surface ligands. The crystalline and monodisperse PeQDs feature a cubic-like shape, with an edge length of 10.1 nm, and a high photoluminescence quantum yield of greater than 90% in toluene solution and 36% as a thin film. We find that the PeQDs are n-type doped following the synthesis but also that they can be p-type and additionally n-type doped by in situ electrochemistry. These combined properties render the PeQDs interesting for the emitter in solution-processed light-emitting electrochemical cells (LECs), and we report a PeQD-LEC with air-stabile electrodes that emits with a narrow emission spectrum (λpeak = 514 nm, full width at half-maximum = 24 nm) and a luminance of 250 cd/m2 at 4 V and a luminance of 1090 cd/m2 at 6.8 V. To reach this performance, it was critical to include a thin solution-processed layer comprising p-type poly(vinyl carbazole) and a tetrahexylammonium tetrafluoroborate ionic liquid between the PeQD emission layer and the anode in order to compensate for the as-synthesized n-type doping of the PeQDs.

    Download full text (pdf)
    fulltext
  • 14.
    Liu, Yong-feng
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. College of Physical Science and Technology, Yangzhou University, Yangzhou, China; Microelectronics Industry Research Institute, Yangzhou University, Yangzhou, China.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gao, Zhaoju
    College of Physical Science and Technology, Yangzhou University, Yangzhou, China.
    Shao, Xiuwen
    College of Physical Science and Technology, Yangzhou University, Yangzhou, China.
    Zhu, Xiaoling
    College of Physical Science and Technology, Yangzhou University, Yangzhou, China.
    Ràfols-Ribé, Joan
    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.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    The influence of the capping ligands on the optoelectronic performance, morphology, and ion liberation of CsPbBr3 perovskite quantum dots2023In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 16, no 7, p. 10626-10633Article in journal (Refereed)
    Abstract [en]

    Perovskite quantum dots (PeQDs) endowed with capping ligands exhibit impressive optoelectronic properties and enable for cost-efficient solution processing and exciting application opportunities. We synthesize and characterize three different PeQDs with the same cubic CsPbBr3 core, but which are distinguished by the ligand composition and density. PeQD-1 features a binary didodecyldimethylammonium bromide (DDAB) and octanoic acid capping ligand system, with a high surface density of 1.53 nm−2, whereas PeQD-2 and PeQD-3 are coated by solely DDAB at a gradually lower surface density. We show that PeQD-1 endowed with highest ligand density features the highest dispersibility in toluene of 150 g/L, the highest photoluminescence quantum yield of 95% in dilute solution and 59% in a neat film, and the largest core-to-core spacing in neat thin films. We further establish that ions are released from the core of PeQD-1 when it is exposed to an electric field, although it comprises a dense coating of one capping ligand per four surface core atoms. We finally exploit these combined findings to the development of a light-emitting electrochemical cell (LEC), where the active layer is composed solely of solution-processed pure PeQDs, without additional electrolytes. In this device, the ion release is utilized as an advantage for the electrochemical doping process and efficient emissive operation of the LEC.

    Download full text (pdf)
    fulltext
  • 15.
    Liu, Yong-feng
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. College of Physical Science and Technology, Yangzhou University, Yangzhou, China.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Wu, Xiuyu
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Boulanger, Nicolas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    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. LunaLEC AB, Umeå, Sweden.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Carbon nanodots: a metal-free, easy-to-synthesize, and benign emitter for light-emitting electrochemical cells2022In: Nano Reseach, ISSN 1998-0124, E-ISSN 1998-0000, Vol. 15, no 6, p. 5610-5618Article in journal (Refereed)
    Abstract [en]

    Light-emitting electrochemical cells (LECs) can be fabricated with cost-efficient printing and coating methods, but a current drawback is that the LEC emitter is commonly either a rare-metal complex or an expensive-to-synthesize conjugated polymer. Here, we address this issue through the pioneering employment of metal-free and facile-to-synthesize carbon nanodots (CNDs) as the emitter in functional LEC devices. Circular-shaped (average diameter = 4.4 nm) and hydrophilic CNDs, which exhibit narrow cyan photoluminescence (peak = 485 nm, full width at half maximum = 30 nm) with a high quantum yield of 77% in dilute ethanol solution, were synthesized with a catalyst-free, one-step solvothermal process using low-cost and benign phloroglucinol as the sole starting material. The propensity of the planar CNDs to form emission-quenching aggregates in the solid state was inhibited by the inclusion of a compatible 2,7-bis(diphenylphosphoryl)-9,9′-spirobifluorene host compound, and we demonstrate that such pristine host-guest CND-LECs turn on to a peak luminance of 118 cd·m−2 within 5 s during constant current-density driving at 77 mA·cm−2.

  • 16.
    Lundberg, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Lindh, Mattias
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Applied Physics and Electronics.
    Toward Efficient and Metal-Free Emissive Devices: A Solution Processed Host Guest Light-Emitting Electrochemical Cell Featuring Thermally Activated Delayed Fluorescence2017In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 34, p. 28810-28816Article in journal (Refereed)
    Abstract [en]

    The next generation of emissive devices should preferably be efficient, low-cost, and environmentally sustainable, and as such utilize all electrically generated excitons (both singlets and triplets) for the light emission, while being free from rare metals such as iridium. Here, we report on a step toward this vision through the design, fabrication, and operation of a host guest light-emitting electrochemical cell (LEC) featuring an organic thermally activated delayed fluorescence (TADF) guest that harvests both singlet and triplet excitons for the emission. The rare-metal-free active material also consists of a polymeric electrolyte and a polymeric compatibilizer for the facilitation of a cost-efficient and scalable solution-based fabrication, and for the use of air-stable electrodes. We report that such TADF-LEC devices can deliver uniform green light emission with a maximum luminance of 228 cd m(-2) when driven by a constant-current density of 770 A m(-2), and 760 cd m(-2) during a voltage ramp, which represents a one-order-of-magnitude improvement in comparison to previous TADF-emitting LECs.

  • 17.
    Lundberg, Petter
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tsuchiya, Youichi
    Lindh, E. Mattias
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Adachi, Chihaya
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Thermally activated delayed fluorescence with 7% external quantum efficiency from a light-emitting electrochemical cell2019In: Nature Communications, E-ISSN 2041-1723, Vol. 10, article id 5307Article in journal (Refereed)
    Abstract [en]

    We report on light-emitting electrochemical cells, comprising a solution-processed single-layer active material and air-stabile electrodes, that exhibit efficient and bright thermally activated delayed fluorescence. Our optimized devices delivers a luminance of 120 cd m−2 at an external quantum efficiency of 7.0%. As such, it outperforms the combined luminance/efficiency state-of-the art for thermally activated delayed fluorescence light-emitting electrochemical cells by one order of magnitude. For this end, we employed a polymeric blend host for balanced electrochemical doping and electronic transport as well as uniform film formation, an optimized concentration (<1 mass%) of guest for complete host-to-guest energy transfer at minimized aggregation and efficient emission, and an appropriate concentration of an electrochemically stabile electrolyte for desired doping effects. The generic nature of our approach is manifested in the attainment of bright and efficient thermally activated delayed fluorescence emission from three different light-emitting electrochemical cells with invariant host:guest:electrolyte number ratio.

    Download full text (pdf)
    fulltext
  • 18.
    Mindemark, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Chemistry, Ångström Laboratory, Uppsala University.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Li, Hu
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ion Transport beyond the Polyether Paradigm: Introducing Oligocarbonate Ion Transporters for Efficient Light-Emitting Electrochemical Cells2018In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 32, article id 1801295Article in journal (Refereed)
    Abstract [en]

    The light-emitting electrochemical cell (LEC) is fundamentally dependent on mobile ions for its operation. In polymer LECs, the mobile ions are commonly provided by dissolving a salt in an ion transporter, with the latter almost invariably being an ether-based compound. Here, the synthesis, characterization, and application of a new class of carbonate-based ion transporters are reported. A polymer LEC, comprising a star-branched oligocarbonate endowed with aliphatic side groups as the ion transporter, features a current efficacy of 13.8 cd A(-1) at a luminance of 1060 cd m(-2), which is a record-high efficiency/luminance combination for a singlet-emitting LEC. It is further established that the design principles of a high-performance carbonate ion transporter constitute the selection of an oligomeric structure over a corresponding polymeric structure and the endowment of the oligomer with functional side chains to render it compatible with the polymeric emitter.

  • 19.
    Mindemark, Jonas
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Kaihovirta, Nikolai
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brandell, Daniel
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    High-Performance Light-Emitting Electrochemical Cells by Electrolyte Design2016In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 28, no 8, p. 2618-2623Article in journal (Refereed)
    Abstract [en]

    Polymer light-emitting electrochemical cells (LECs) are inherently dependent on a suitable electrolyte for proper function. Here, we design and synthesize a series of alkyl carbonate-capped star-branched oligoether-based electrolytes with large electrochemical stability windows, facile ion release, and high compatibility with common light-emitting materials. LECs based on such designed electrolytes feature fast turn-on, a long operational lifetime of 1400 h at >100 cd m(-2) and a record-high power conversion efficiency of 18.1 lm W-1, when equipped with an external outcoupling film.

  • 20. Mone, Mariza
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Genene, Zewdneh
    Murto, Petri
    Jevric, Martyn
    Zou, Xianshao
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Abdulahi, Birhan A.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mammo, Wendimagegn
    Andersson, Mats R.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Ergang
    Near-Infrared Emission by Tuned Aggregation of a Porphyrin Compound in a Host-Guest Light-Emitting Electrochemical Cell2021In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 9, no 6, article id 2001701Article in journal (Refereed)
    Abstract [en]

    The synthesis of 5,10,15,20-tetrakis((5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridin-2-yl)ethynyl)porphyrin zinc(II) (Por4NT), a near-infrared (NIR) emitting compound, comprising a zinc porphyrin core linked with triple bonds through its meso positions to four 5,10-bis((2-hexyldecyl)oxy)dithieno[3,2-c:3′,2′-h][1,5]naphthyridine (NT) arms is reported. Por4NT featured high solubility in common non-polar solvents, which is ideal for easy processing through solution techniques, and high photoluminescence (PL) efficiency of ≈30% in dilute toluene solution. It also exhibited a strong tendency for aggregation because of its flat conformation, and this aggregation resulted in a strong redshifted emission and a drop in PL efficiency. A well-matched PBDTSi-BDD-Py "host" terpolymer is therefore designed, which is capable of mitigating the aggregation of the Por4NT "guest". An optimized blend of the host, guest, and an ionic-liquid electrolyte is utilized as the active material in a light-emitting electrochemical cell (LEC), which delivered strong NIR radiance of 134 µW cm-2 with a long wavelength maximum at 810 nm at a low drive voltage of 5.0 V. The attainment of the strong NIR emission from the host–guest LEC is attributed to a tuned aggregation of the Por4NT emitter, which resulted in the desired aggregation-induced redshift of the emission at a reasonably retained efficiency.

    Download full text (pdf)
    fulltext
  • 21. Mone, Mariza
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Murto, Petri
    Abdulahi, Birhan A.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mammo, Wendimagegn
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Ergang
    Star-Shaped Diketopyrrolopyrrole-Zinc Porphyrin that Delivers 900 nm Emission in Light-Emitting Electrochemical Cells2019In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 31, no 23, p. 9721-9728Article in journal (Refereed)
    Abstract [en]

    The development and application of a deep near-infrared (NIR) emitting star-shaped diketopyrrolopyrrole–Zn-porphyrin compound, ZnP(TDPP)4, is reported. The structure, conjugation, and planarity of the porphyrin compound were carefully tuned by molecular design, which resulted in a low-energy photoluminescence peak at 872 nm. The ZnP(TDPP)4 compound was employed as the emissive guest in light-emitting electrochemical cells (LECs), which also comprised the conjugated polymer poly[1,3-bis(2-ethylhexyl)-5-(5-(6-methyl-4,8-bis(5-(tributylsilyl)thiophen-2-yl)benzo[1,2-b:4,5-b′]dithiophen-2-yl)thiophen-2-yl)-7-(5-methylthiophen-2-yl)-4H,8H-benzo[1,2-c:4,5-c′]dithiophene-4,8-dione] (PBDTSi-BDD) as the majority host, an ionic liquid as the electrolyte, and two air-stabile electrodes. These systematically optimized host–guest LECs featured a peak electroluminescence at 900 nm, which was delivered at a significant radiance of 36 μW/cm2 and at a low drive voltage of 3.8 V. It is notable that this is the most redshifted NIR emission attained from an LEC device to date, and as such, this work introduces Zn porphyrins as a sustainable and tunable option for emerging emissive NIR applications.

  • 22.
    Munar, Antoni
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Shedding light on the operation of polymer light-emitting electrochemical cells using impedance spectroscopy2012In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 22, no 7, p. 1511-1517Article in journal (Refereed)
    Abstract [en]

    A combination of impedance spectroscopy, device characterization, and modeling is used to pinpoint key processes in the operation of polymer light-emitting electrochemical cells (LECs). At low applied voltage, electric double layers with a thickness of similar to 23 nm are shown to exist at the electrode interfaces. At voltages exceeding the bandgap potential of the conjugated polymer (V = 2.5 V for superyellow), a light-emitting pn junction forms in situ, with a steady-state structure that is found to depend strongly on the applied voltage. This is exemplified by that the effective pn junction thickness (dpn) for a device with an interelectrode gap of 90 nm decreases from similar to 23 nm at 2.5 V to similar to 6 nm at 3.9 V. The current increases with decreasing dpn in a concerted manner, while the brightness reaches its peak at V = 3.4 V when dpn similar to 10 nm. The existence of an optimum dpn for high brightness in LECs is attributed to an offset between an increase in the exciton formation rate with decreasing dpn, due to an increasing current, and a simultaneous decrease in the exciton radiative decay rate, when an increasing fraction of excitons diffuses away from the pn junction into the surrounding non-radiative doping regions.

  • 23. 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, E-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.

  • 24.
    Ràfols-Ribé, Joan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gracia-Espino, Eduardo
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Jenatsch, Sandra
    Lundberg, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    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.
    Elucidating Deviating Temperature Behavior of Organic Light-Emitting Diodes and Light-Emitting Electrochemical Cells2021In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 9, no 1, article id 2001405Article in journal (Refereed)
    Abstract [en]

    Organic light-emitting diodes (OLEDs) and light-emitting electrochemical cells (LECs) exhibit different operational modes that render them attractive for complementary applications, but their dependency on the device temperature has not been systematically compared. Here, the effects of a carefully controlled device temperature on the performance of OLEDs and LECs based on two common emissive organic semiconductors are investigated. It is found that the peak luminance and current efficacy of the two OLEDs are relatively temperature independent, whereas, the corresponding LECs exhibit a significant increase by approximate to 85% when the temperature is changed from 20 to 80 degrees C. A combination of simulations and measurements reveal that this deviating behavior is consistent with a shift of the emission zone from closer to the transparent anode toward the center of the active material for both the OLEDs and the LECs, which in turn can be induced by a stronger positive temperature dependence of the mobility of the holes than the electrons.

    Download full text (pdf)
    fulltext
  • 25.
    Ràfols-Ribé, Joan
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Robinson, Nathaniel D.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Top, Michiel
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Self-Heating in Light-Emitting Electrochemical Cells2020In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 30, no 33, article id 1908649Article, review/survey (Refereed)
    Abstract [en]

    Electroluminescent devices become warm during operation, and their performance can, therefore, be severely limited at high drive current density. Herein, the effects of this self‐heating on the operation of a light‐emitting electrochemical cell (LEC) are systematically studied. A drive current density of 50 mA cm−2 can result in a local device temperature for a free‐standing LEC that exceeds 50 °C within a short period of operation, which in turn induces premature device degradation as manifested in the rapidly decreasing luminance and increasing voltage. Furthermore, this undesired self‐heating for a free‐standing thin‐film LEC can be suppressed by the employment of a device architecture featuring high thermal conductance and a small emission‐area fill factor, since the corresponding improved heat conduction to the nonemissive regions facilitates more efficient heat transfer to the ambient surroundings. In addition, the reported differences in performance between small‐area and large‐area LECs as well as between flexible‐plastic and rigid‐glass LECs are rationalized, culminating in insights that can be useful for the rational design of LEC devices with suppressed self‐heating and high performance.

    Download full text (pdf)
    fulltext
  • 26. Shafikov, Marsel Z.
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Bodensteiner, Michael
    Kozhevnikov, Valery N.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    An efficient heterodinuclear Ir(III)/Pt(II) complex: synthesis, photophysics and application in light-emitting electrochemical cells2019In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 7, no 34, p. 10672-10682Article in journal (Refereed)
    Abstract [en]

    We report on the design, synthesis, characterization and successful application of a heterodinuclear Ir(III)/Pt(II) complex endowed with two 4,6-diphenylpyrimidine ligands and two acetylacetonate ligands, with one of the former being the rigid bridging unit between the two metal centers. The heterodinuclear complex exhibits red phosphorescence with a high quantum yield of Phi(PL) = 85% and a short room-temperature decay time of tau = 640 ns in degassed toluene solution. The high efficiency of the spin-forbidden T-1 -> S-0 transition is demonstrated to originate in a strong spin-orbit coupling of the T-1 state with a manifold of excited singlet states, which contributes to the record-breaking zero-field splitting of the T-1 state of 240 cm(-1). The high-solubility and non-ionic hetero-dinuclear complex was employed as the emissive guest compound in host-guest light-emitting electrochemical cells, and such optimized devices delivered vibrant red emission (lambda(peak) = 615 nm) with a second-fast turn-on and a high external quantum efficiency of 2.7% at a luminance of 265 cd m(-2).

  • 27.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå.
    Buchholz, Herwig A.
    Merck KGaA, Darmstadt, Germany .
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    On the selection of a host compound for efficient host-guest light-emitting electrochemical cells2015In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 3, no 31, p. 8114-8120Article in journal (Refereed)
    Abstract [en]

    A light-emitting electrochemical cell (LEC) is characterized by its electrochemical doping operation that facilitates advantages as regards device fabrication and functionality, but it currently suffers from the drawback that the efficiency at significant luminance is not very high. A viable solution to this setback could be the implementation of a host-guest active material, where the majority host transports the electronic charge and the guest is a triplet emitter that features an appropriate energy structure for facile exciton transfer and trapping as well as for efficient light emission. Here, we demonstrate that an additional critical property of a functional host-guest LEC is that the host can be electrochemically p- and n-type doped, as can be deduced from screening studies on open planar devices and by cyclic voltammetry. LEC devices based on hosts that do not fulfill this fundamental criterion are shown to suffer from low luminance and poor efficiency, whereas host-guest LECs, based on a host material capable of electrochemical doping, exhibit a much improved luminance and efficiency, with the efficiency being well retained at high luminance values also.

  • 28.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Buchholz, Herwig A
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    White Light from a Light-Emitting Electrochemical Cell: Controlling the Energy-Transfer in a Conjugated Polymer/Triplet-Emitter Blend2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 46, p. 25955-25960Article in journal (Refereed)
    Abstract [en]

    We report on the attainment of broadband white light emission from a hostguest light-emitting electrochemical cell, comprising a blue-emitting conjugated polymer as the majority host and a red-emitting small-molecule triplet emitter as the minority guest. An analysis of the energy structure reveals that host-to-guest energy transfer can be effectuated by both Forster and Dexter processes, and through a careful optimization of the active material composition partial energy transfer and white emission is accomplished at a low guest concentration of 0.5%. By adding a small amount of a yellow-emitting conjugated polymer to the active material, white light emission with a high color rendering index of 79, and an efficiency of 4.3 cd/A at significant luminance (>200 cd/m2), is realized.

  • 29.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    dos Santos, John Marques
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zysman-Colman, Eli
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, St Andrews, United Kingdom.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Introducing MR-TADF emitters into light-emitting electrochemical cells for narrowband and efficient emission2023In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 33, article id 2306170Article in journal (Refereed)
    Abstract [en]

    Organic semiconductors that emit by the process of multi-resonance thermally activated delayed fluorescence (MR-TADF) can deliver narrowband and efficient electroluminescence while being processable from solvents and metal-free. This renders them attractive for use as the emitter in sustainable light-emitting electrochemical cells (LECs), but so far reports of narrowband and efficient MR-TADF emission from LEC devices are absent. Here, this issue is addressed through careful and systematic material selection and device development. Specifically, the authors show that the detrimental aggregation tendency of an archetypal rigid and planar carbazole-based MR-TADF emitter can be inhibited by its dispersion into a compatible carbazole-based blend host and an ionic-liquid electrolyte, and it is further demonstrated that the tuning of this active material results in a desired balanced p- and n-type electrochemical doping, a high solid-state photoluminescence quantum yield of 91%, and singlet and triplet trapping on the MR-TADF guest emitter. The introduction of this designed metal-free active MR-TADF material into a LEC, employing air-stabile electrodes, results in bright blue electroluminescence of 500 cd m−2, which is delivered at a high external quantum efficiency of 3.8% and shows a narrow emission profile with a full-width-at-half-maximum of 31 nm.

    Download full text (pdf)
    fulltext
  • 30.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC, Umeå, Sweden.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC, Umeå, Sweden.
    Light-Emitting Electrochemical Cells: A Review on Recent Progress2016In: Topics in Current Chemistry, ISSN 2365-0869, Vol. 374, no 4, article id 40Article, review/survey (Refereed)
    Abstract [en]

    The light-emitting electrochemical cell (LEC) is an area-emitting device, which features a complex turn-on process that ends with the formation of a p-n junction doping structure within the active material. This in-situ doping transformation is attractive in that it promises to pave the way for an unprecedented low-cost fabrication of thin and light-weight devices that present efficient light emission at low applied voltage. In this review, we present recent insights regarding the operational mechanism, breakthroughs in the development of scalable and adaptable solution-based methods for cost-efficient fabrication, and successful efforts toward the realization of LEC devices with improved efficiency and stability.

  • 31.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Quest for an Appropriate Electrolyte for High-Performance Light-Emitting Electrochemical Cells2010In: Journal of physical chemistry letters, Vol. 1, no 18, p. 2727-2732Article in journal (Refereed)
    Abstract [en]

    The electrolyte plays a critical role in the operation of light-emitting electrochemical cells (LECs), and the LEC operational stability and efficiency can be severely limited by electrolyte-induced side reactions. Here we employ a trimethylolpropane-LiCF3SO3 electrolyte with a particularly wide electrochemical stability window and for-the-purpose appropriate transport properties to minimize cathodic side reactions and to keep the emission zone free from electrolyte species during steady-state operation. We utilize an optimized blend of this electrolyte and the conjugated polymer superyellow as the active material sandwiched between air-stable electrodes, and we demonstrate that such LEC devices can exhibit a notably respectable operational lifetime (57 days of uninterrupted operation at a brightness of >100 cd/m2) and a high efficiency (>10 lm/W at >100 cd/m2).

  • 32.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Irgum, Knut
    Umeå University, Faculty of Science and Technology, Department of Chemistry.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Chemical stabilization of doping in conjugated polymers2010In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 11, no 6, p. 1079-1087Article in journal (Refereed)
    Abstract [en]

    Conjugated polymers can be electrochemically doped to high-conductivity states under applied voltage, but such in situ formed doping structures are dynamic and dissipate when the formation voltage is removed. For some applications it is highly desirable to permanently stabilize the doping after its formation. Here, we report and compare results on four different approaches to chemical stabilization of an emissive and rectifying p–n junction doping structure in a light-emitting electrochemical cell (LEC) application: (i) polymerization of the dopant counter-ions, (ii) polymerization of the counter-ions utilizing a radical-initiator compound, (iii) polymerization of the ion-transport material, and (iv) polymerization of both the counter-ions and the ion-transport material utilizing a radical-initiator compound. We found that approach (i) resulted in LEC devices with poor stability, current rectification and light-emission, and that approach (ii) solely yielded a notable improvement in the light-emission. Approach (iii) resulted in good current rectification and stability, but the overall best results were clearly attained with approach (iv) as such stabilized LEC devices exhibited a respectable current rectification ratio of 2000, as well as a decent light-emission efficiency and long-term stability under idle conditions.

  • 33.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Larsen, Christian
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Ràfols-Ribé, Joan
    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. LunaLEC AB, Umeå, Sweden.
    An Amorphous Spirobifluorene-Phosphine-Oxide Compound as the Balanced n-Type Host in Bright and Efficient Light-Emitting Electrochemical Cells with Improved Stability2021In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 9, no 7, article id 2002105Article in journal (Refereed)
    Abstract [en]

    A rational host–guest concept design for the attainment of high efficiency at strong luminance from light‐emitting electrochemical cells (LECs) by suppression of exciton‐polaron quenching [Tang et al., Nature Communications 20178, 1190] has been reported. However, a practical drawback with the presented host–guest LEC devices was that the operational stability is insufficient for many applications. Here, a systematic study is performed, revealing that a major culprit for the limited operational stability is that the employed n‐type host, 1,3‐bis[2‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazo‐5‐yl]benzene (OXD‐7), has a strong propensity for crystallization and that this crystallization results in a detrimental phase separation of the constituents in the active material during device operation. The authors, therefore, identify an alternative class of concept‐functional n‐type hosts in the form of spirobifluorene‐phosphine‐oxide compounds, and report that the replacement of OXD‐7 with amorphous 2,7‐bis(diphenylphosphoryl)‐9,9′‐spirobifluorene results in a much improved operational lifetime of 700 h at >100 cd m−2 during constant‐bias driving at an essentially retained high current efficacy of 37.9 cd A−1 and a strong luminance of 2940 cd m−2.

    Download full text (pdf)
    fulltext
  • 34.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Liu, Yong-feng
    Umeå University, Faculty of Science and Technology, Department of Physics. College of Physical Science and Technology, Yangzhou University, Yangzhou, China.
    Opoku, Henry
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gregorsson, Märta
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Zhang, Peijuan
    School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Material Chemistry, Xi'an Jiao Tong University, Xi'an, China.
    Auroux, Etienne
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Dang, Dongfeng
    School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Material Chemistry, Xi'an Jiao Tong University, Xi'an, China.
    Mudring, Anja-Verena
    Intelligent Advanced Materials (iAM), Department of Biological and Chemical Engineering and iNANO, Aarhus University, Aarhus C, Denmark.
    Wågberg, Thomas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fluorescent carbon dots from birch leaves for sustainable electroluminescent devices2023In: Green Chemistry, ISSN 1463-9262, E-ISSN 1463-9270, Vol. 25, no 23, p. 9884-9895Article in journal (Refereed)
    Abstract [en]

    The shift from depleting petroleum compounds to regenerating biomass as the raw material for organic semiconductors is a prerequisite if organic electronics is to become truly sustainable. Here, we report on a one-pot solvothermal synthesis of a biomass-based carbon dot (bio-CD) fluorescent semiconductor, using birch leaves as the sole raw material. These bio-CDs are highly soluble in ethanol (45 g L-1), and deliver deep-red and narrowband emission (peak wavelength = 675 nm, full width at half maximum, FWHM = 28 nm) at a high photoluminescence quantum yield of 26% in ethanol solution. Systematic structural characterization shows that molecular pheophytin a is the single fluorophore, and that this fluorophore is localized in the bulk of the bio-CD away from its polar surface. The functionality of the birch-leaf-derived bio-CDs in sustainable organic electronics is demonstrated by its employment as the printable emitter in a light-emitting electrochemical cell, which delivers narrowband deep-red luminance of 110 cd m-2, with a FWHM of 29 nm, at an external quantum efficiency of 0.29%. This study thus reveals a promising avenue for the functional benign synthesis and the practical solution-based implementation of narrowband bio-CDs in sustainable optoelectronic technologies.

    Download full text (pdf)
    fulltext
  • 35.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Lundberg, Petter
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tsuchiya, Youichi
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka, Nishi-ku, Fukuoka, Japan.
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Liu, Yong-feng
    Umeå University, Faculty of Science and Technology, Department of Physics. College of Physical Science and Technology & Microelectronics Industry Research Institute, Yangzhou University, Yangzhou, China.
    Wang, Jia
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Adachi, Chihaya
    Center for Organic Photonics and Electronics Research (OPERA), Kyushu University, Motooka, Nishi-ku, Fukuoka, Japan.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Efficient and bright blue thermally activated delayed fluorescence from light-emitting electrochemical cells2022In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, no 44, article id 2205967Article in journal (Refereed)
    Abstract [en]

    Light-emitting electrochemical cells (LECs) comprising metal-free molecules that emit by the process of thermally activated delayed fluorescence (TADF) can be both sustainable and low cost. However, the blue emission performance of current TADF-LECs is unfortunately poor, which effectively prohibits their utilization in important applications, such as illumination and full-color displays. Here, this drawback is addressed through the development of a TADF-LEC, which delivers blue light emission (peak wavelength = 475 nm) with a high external quantum efficiency of 5.0%, corresponding to a current efficacy of 9.6 cd A-1. It is notable that this high efficiency is attained at bright luminance of 740 cd m-2, and that the device turn-on is very fast. It is demonstrated that this accomplishment is enabled by the blending of a carbazole-based 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-methylphenyl)-3,6-dimethyl-9H-carbazole guest emitter with a compatible carbazole-based tris(4-carbazoyl-9-ylphenyl)amine:2,6-bis(3-(carbazol-9-yl)phenyl)pyridine blend-host for the attainment of bipolar electrochemical doping, balanced electron/hole transport, and exciplex-effectuated host-to-guest energy transfer.

    Download full text (pdf)
    fulltext
  • 36.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mindemark, Jonas
    Department of Chemistry − Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Araujo, Carlos Moyses Graca
    Materials Theory Division, Department of Physics and Astronomy, Uppsala University, Uppsala, Sweden.
    Brandell, Daniel
    Department of Chemistry − Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. ludvig.edman@physics.umu.se.
    Identifying Key Properties of Electrolytes for Light-Emitting Electrochemical Cells2014In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 26, no 17, p. 5083-5088Article in journal (Refereed)
    Abstract [en]

    The electrolyte is a key component in light-emitting electrochemical cells (LECs), as it facilitates in situ electrochemical doping and associated attractive device features. LiCF3SO3 dissolved in hydroxyl-capped trimethylolpropane ethoxylate (TMPE-OH) constitutes an electrolyte with which we have attained high stability and efficiency for polymer LECs, but the turn-on time of such devices is unfortunately slow. By replacing hydroxyl with methoxy as the TMPE end-group, we produced LECs with a desired combination of high efficiency, good stability, and fast turn-on time. Specifically, we showed that the turn-on time to high luminance (300 cd/m(2)) at a current density of 7.7 mA/cm(2) is lowered from 1740 to 16 s, that the efficiency is improved by similar to 20%, and that the other device properties are either maintained or improved. In a parallel modeling and experimental effort, we demonstrated that the faster kinetics following the shift in the TMPE end-group is attributed to a marked decrease in the level of both inter- and intramolecular interactions of the electrolyte, as manifested in a lowered electrolyte viscosity, faster ion transport, and more facile ion release during doping.

  • 37.
    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.

  • 38.
    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.

  • 39.
    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.

  • 40.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pan, Junyou
    Buchholz, Herwig A.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    White Light from a Single-Emitter Light-Emitting Electrochemical Cell2013In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 135, no 9, p. 3647-3652Article in journal (Refereed)
    Abstract [en]

    We report a novel and generic approach for attaining white light from a single-emitter light-emitting electrochemical cell (LEC). With an active-layer comprising a multifluorophoric conjugated copolymer (MCP) and an electrolyte designed to inhibit MCP energy-transfer interactions during LEC operation, we are able to demonstrate LECs that emit broad-band white light with a color rendering index of 82, a correlated-color temperature of 4000 K, and a current conversion efficacy of 3.8 cd/A. It is notable that this single-emitter LEC configuration eliminates color-drift problems stemming from phase separation, which are commonly observed in conventional blended multiemitter devices. Moreover, the key role of the electrolyte in limiting undesired energy-transfer reactions is highlighted by the observation that an electrolyte-free organic light-emitting diode comprising the same MCP emits red light.

  • 41.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pan, Junyou
    Merck KGaA.
    Buchholz, Herwig
    Merck KGgA.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    White light-emitting electrochemical cell2011In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 3, no 9, p. 3384-3388Article in journal (Refereed)
    Abstract [en]

    We report a light-emitting electrochemical cell (LEC) with air-stable electrodes and a solution-processed single-layer active material that emits warm-white light (CIE coordinates = (0.39, 0.43); color rendering index =83) with significant brightness (B) at a low voltage. The carefully tuned trichromatic device exhibits a short turn-on time (5 s to B > 100 cd/m2), high efficiency (3.1 cd/A at B = 240 cd/m2) and good operational stability (17 h at B > 100 cd/m2). We also report a blue LEC with a highly respectable set of device properties in the form of a turn-on time of 5 s, an efficiency of 3.6 lm/W and 5.6 cd/A, and an uninterrupted operational lifetime of 25 h. Finally, by analyzing data from trichromatic and monochromatic devices as well as from the constituent fluorescent CPs, we are able to point out a viable path toward further improvements in the performance of the white-emitting LEC.

  • 42.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Sandström, Andreas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Fang, Junfeng
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    A Solution-Processed Trilayer Electrochemical Device: Localizing the Light Emission for Optimized Performance2012In: Journal of the American Chemical Society, ISSN 0002-7863, E-ISSN 1520-5126, Vol. 134, no 34, p. 14050-14055Article in journal (Refereed)
    Abstract [en]

    We present a solution-processed trilayer light-emitting device architecture, comprising two hydrophobic and mobile-ion-containing "transport layers" sandwiching a hydrophilic and ion-free "intermediate layer", which allows for lowered self-absorption, minimized electrode quenching, and tunable light emission. Our results reveal that the transport layers can be doped in situ when a voltage is applied, that the intermediate layer as desired can contribute significantly to the light emission, and that the key to a successful operation is the employment of a porous and (similar to 5-10 nm) thin intermediate layer allowing for facile ion transport. We report that such a solution-processed device, comprising a thick trilayer material (similar to 250 nm) and air-stable electrodes, emits blue light (lambda(peak) = 450, 484 nm) with high efficiency (5.3 cd/A) at a low drive voltage of 5 V.

  • 43.
    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, 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.

    Download full text (pdf)
    fulltext
  • 44.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tan, Wan-Yi
    Zhu, Xu-Hui
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Small-molecule light-emitting electrochemical cells: evidence for in situ electrochemical doping and functional operation2013In: Chemical Communications, ISSN 1359-7345, E-ISSN 1364-548X, Vol. 49, no 43, p. 4926-4928Article in journal (Refereed)
    Abstract [en]

    We demonstrate that non-ionic small molecules (SMs) can function as the doping and emissive compound in light-emitting electrochemical cells (LECs), and that high brightness and decent efficiency can be attained for such devices. It is plausible that the expansion of the LEC library, to include easy-to-purify and tunable non-ionic SM compounds, could represent a viable path towards improved LEC devices.

  • 45.
    Tang, Shi
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Wang, Zhi
    School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Material Chemistry, Xi'an Jiao Tong University, Xi'an, China.
    Xu, Yanzi
    School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Material Chemistry, Xi'an Jiao Tong University, Xi'an, China.
    Ma, Huili
    Key Laboratory of Flexible Electronics (KLOFE) & Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing, China.
    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, Umeå, Sweden.
    Dang, Dongfeng
    School of Chemistry, Xi'an Key Laboratory of Sustainable Energy Material Chemistry, Xi'an Jiao Tong University, Xi'an, China.
    Wang, Ergang
    Department of Chemistry and Chemical Engineering/Applied Chemistry, Chalmers University of Technology, Gothenburg, Sweden.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, Umeå, Sweden.
    Aggregation-induced emission by molecular design: a route to high-performance light-emitting electrochemical cells2023In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 62, no 23, article id e202302874Article in journal (Refereed)
    Abstract [en]

    The emission efficiency of organic semiconductors (OSCs) often suffers from aggregation caused quenching (ACQ). An elegant solution is aggregation-induced emission (AIE), which constitutes the design of the OSC so that its morphology inhibits quenching π–π interactions and non-radiative motional deactivation. The light-emitting electrochemical cell (LEC) can be sustainably fabricated, but its function depends on motion of bulky ions in proximity of the OSC. It is therefore questionable whether the AIE morphology can be retained during LEC operation. Here, we synthesize two structurally similar OSCs, which are distinguished by that 1 features ACQ while 2 delivers AIE. Interestingly, we find that the AIE-LEC significantly outperforms the ACQ-LEC. We rationalize our finding by showing that the AIE morphology remains intact during LEC operation, and that it can feature appropriately sized free-volume voids for facile ion transport and suppressed non-radiative excitonic deactivation.

    Download full text (pdf)
    fulltext
  • 46.
    Wang, Jia
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, SE-90719 Umea, Sweden.
    Sandström, Andreas
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics. LunaLEC AB, SE-90719 Umea, Sweden.
    Combining an Ionic Transition Metal Complex with a Conjugated Polymer for Wide-Range Voltage-Controlled Light-Emission Color2015In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 7, no 4, p. 2784-2789Article in journal (Refereed)
    Abstract [en]

    We report on voltage-controlled electroluminescence (EL) over a broad range of colors from a two-luminophor (2L) light-emitting electrochemical cell (LEC), comprising a blend of a majority blue-emitting conjugated polymer (blue-CP), a minority red-emitting ionic transition metal complex (red-iTMC), and an ion-transporting compound as the active layer. The EL color is reversibly shifted from red, over orange, pink, and white, to blue by simply changing the applied voltage from 3 to 7 V. An analysis of our results suggests that the low concentration of immobile cations intrinsic to this particular device configuration controls the electron injection and thereby the EL color: at low voltage, electrons are selectively injected into the low-barrier minority red-iTMC, but with increasing voltage the injection into the high-barrier majority blue-CP is gradually improved.

  • 47.
    Wang, Jingxiang
    et al.
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, Fife, St Andrews, United Kingdom.
    Hafeez, Hassan
    Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, United Kingdom.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Matulaitis, Tomas
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, Fife, St Andrews, United Kingdom.
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Samuel, Ifor D. W.
    Organic Semiconductor Centre, SUPA School of Physics and Astronomy, University of St Andrews, St Andrews, United Kingdom.
    Zysman-Colman, Eli
    Organic Semiconductor Centre, EaStCHEM School of Chemistry, University of St Andrews, Fife, St Andrews, United Kingdom.
    Highly efficient organic light-emitting diodes and light-emitting electrochemical cells employing multiresonant thermally activated delayed fluorescent emitters with bulky donor or acceptor peripheral groups2024In: Aggregate, ISSN 2766-8541Article in journal (Refereed)
    Abstract [en]

    Multiresonant thermally activated delayed fluorescence (MR-TADF) emitters have been the focus of extensive design efforts as they are recognized to show bright, narrowband emission, which makes them very appealing for display applications. However, the planar geometry and relatively large singlet–triplet energy gap lead to, respectively, severe aggregation-caused quenching (ACQ) and slow reverse intersystem crossing (RISC). Here, a design strategy is proposed to address both issues. Two MR-TADF emitters triphenylphosphine oxide (TPPO)-tBu-DiKTa and triphenylamine (TPA)-tBu-DiKTa have been synthesized. Twisted ortho-substituted groups help increase the intermolecular distance and largely suppress the ACQ. In addition, the contributions from intermolecular charge transfer states in the case of TPA-tBu-DiKTa help to accelerate RISC. The organic light-emitting diodes (OLEDs) with TPPO-tBu-DiKTa and TPA-tBu-DiKTa exhibit high maximum external quantum efficiencies (EQEmax) of 24.4% and 31.0%, respectively. Notably, the device with 25 wt% TPA-tBu-DiKTa showed both high EQEmax of 28.0% and reduced efficiency roll-off (19.9% EQE at 1000 cd m−2) compared to the device with 5 wt% emitter (31.0% EQEmax and 11.0% EQE at 1000 cd m−2). The new emitters were also introduced into single-layer light-emitting electrochemical cells (LECs), equipped with air-stable electrodes. The LEC containing TPA-tBu-DiKTa dispersed at 0.5 wt% in a matrix comprising a mobility-balanced blend-host and an ionic liquid electrolyte delivered blue luminance with an EQEmax of 2.6% at 425 cd m−2. The high efficiencies of the OLEDs and LECs with TPA-tBu-DiKTa illustrate the potential for improving device performance when the DiKTa core is decorated with twisted bulky donors.

    Download full text (pdf)
    fulltext
  • 48. Xiong, Wenjing
    et al.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Murto, Petri
    Zhu, Weiguo
    Edman, Ludvig
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wang, Ergang
    Combining Benzotriazole and Benzodithiophene Host Units in Host-Guest Polymers for Efficient and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells2019In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 15, article id 1900280Article in journal (Refereed)
    Abstract [en]

    A set of host-guest copolymers with alternating benzodithiophene and benzotriazole (BTz) derivatives as host units and 4,7-bis(5-bromothiophen-2-yl)-benzo[c][1,2,5]thiadiazole as the minority guest are synthesized, characterized, and evaluated for applications. A light-emitting electrochemical cell (LEC) comprising such a host-guest copolymer delivers fast-response near-infrared (NIR) emission peaked at 723 nm with a high radiance of 169 mu W cm(-2) at a low drive voltage of 3.6 V. The NIR-LEC also features good stability, as the peak NIR output only drops by 8% after 350 h of continuous operation. It is, however, found that the LEC performance is highly sensitive to the detailed chemical structure of the host backbone, and that the addition of electron-donating thiophene bridging units onto the BTz unit is highly positive while the inclusion of fluorine atoms results in a drastically lowered performance, presumably because of the emergence of hydrogen bonding within the active material.

  • 49.
    Zhang, Xiaoying
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ràfols-Ribé, Joan
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Mindemark, Jonas
    Department of Chemistry − Ångström Laboratory, Uppsala University, Uppsala, Sweden.
    Tang, Shi
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lindh, Mattias
    Sustainable Resource Conversion unit, Biorefinery and Energy department, RISE Research Institutes of Sweden AB, Storgatan 65, Umeå, Sweden.
    Gracia-Espino, Eduardo
    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.
    Efficiency roll-off in light-emitting electrochemical cells2024In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095Article in journal (Refereed)
    Abstract [en]

    Understanding “efficiency roll-off” (i.e., the drop in emission efficiency with increasing current) is critical if efficient and bright emissive technologies are to be rationally designed. Emerging light-emitting electrochemical cells (LECs) can be cost- and energy-efficiently fabricated by ambient-air printing by virtue of the in situ formation of a p-n junction doping structure. However, this in situ doping transformation renders a meaningful efficiency analysis challenging. Herein, a method for separation and quantification of major LEC loss factors, notably the outcoupling efficiency and exciton quenching, is presented. Specifically, the position of the emissive p-n junction in common singlet-exciton emitting LECs is measured to shift markedly with increasing current, and the influence of this shift on the outcoupling efficiency is quantified. It is further verified that the LEC-characteristic high electrochemical-doping concentration renders singlet-polaron quenching (SPQ) significant already at low drive current density, but also that SPQ increases super-linearly with increasing current, because of increasing polaron density in the p-n junction region. This results in that SPQ dominates singlet-singlet quenching for relevant current densities, and significantly contributes to the efficiency roll-off. This method for deciphering the LEC efficiency roll-off can contribute to a rational realization of all-printed LEC devices that are efficient at highluminance.

    Download full text (pdf)
    fulltext
1 - 49 of 49
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