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Publications (10 of 156) Show all publications
Hultman, L., Mazur, S., Ankarcrona, C., Palmqvist, A., Abrahamsson, M., Antti, M.-L., . . . Berggren, M. (2024). Advanced materials provide solutions towards a sustainable world [Letter to the editor]. Nature Materials, 23(2), 160-161
Open this publication in new window or tab >>Advanced materials provide solutions towards a sustainable world
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2024 (English)In: Nature Materials, ISSN 1476-1122, E-ISSN 1476-4660, Vol. 23, no 2, p. 160-161Article in journal, Letter (Other academic) Published
Place, publisher, year, edition, pages
Nature Publishing Group, 2024
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-220887 (URN)10.1038/s41563-023-01778-9 (DOI)38307974 (PubMedID)2-s2.0-85183827413 (Scopus ID)
Available from: 2024-02-14 Created: 2024-02-14 Last updated: 2024-02-14Bibliographically approved
Zhang, X., Ràfols-Ribé, J., Mindemark, J., Tang, S., Lindh, M., Gracia-Espino, E., . . . Edman, L. (2024). Efficiency roll-off in light-emitting electrochemical cells. Advanced Materials
Open this publication in new window or tab >>Efficiency roll-off in light-emitting electrochemical cells
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2024 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2024
Keywords
efficiency roll-off, light-emitting electrochemical cell, p-n junction position, singlet-polaron quenching, singlet-singlet quenching
National Category
Atom and Molecular Physics and Optics Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-220016 (URN)10.1002/adma.202310156 (DOI)001143796900001 ()38211953 (PubMedID)2-s2.0-85182424168 (Scopus ID)
Funder
Swedish Research Council, 2019-02345Swedish Research Council, 2021-04778Swedish Energy Agency, 50779-1Swedish Energy Agency, P2021-00032Bertil & Britt Svenssons Stiftelse för BelysningsteknikThe Kempe FoundationsKnut and Alice Wallenberg Foundation, KAW 2022.0381Knut and Alice Wallenberg Foundation, WISE-AP01-D02EU, European Research Council, 101096650
Available from: 2024-01-30 Created: 2024-01-30 Last updated: 2024-01-30
Wang, J., Hafeez, H., Tang, S., Matulaitis, T., Edman, L., Samuel, I. D. W. & Zysman-Colman, E. (2024). Highly efficient organic light-emitting diodes and light-emitting electrochemical cells employing multiresonant thermally activated delayed fluorescent emitters with bulky donor or acceptor peripheral groups. Aggregate
Open this publication in new window or tab >>Highly efficient organic light-emitting diodes and light-emitting electrochemical cells employing multiresonant thermally activated delayed fluorescent emitters with bulky donor or acceptor peripheral groups
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2024 (English)In: Aggregate, ISSN 2766-8541Article in journal (Refereed) Epub ahead of print
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2024
Keywords
aggregation-caused quenching, electroluminescence, long-range charge transfer, OLED, organic semiconductor, short-range charge transfer, TADF
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-224248 (URN)10.1002/agt2.571 (DOI)2-s2.0-85192166923 (Scopus ID)
Funder
Swedish Research Council, 2019-02345Swedish Research Council, 2021–04778Swedish Energy Agency, 50779-1Swedish Energy Agency, P2021-00032Knut and Alice Wallenberg FoundationEU, European Research Council, 101096650
Available from: 2024-05-15 Created: 2024-05-15 Last updated: 2024-05-15Bibliographically approved
Filate, T. T., Tang, S., Genene, Z., Edman, L., Mammo, W. & Wang, E. (2024). Hydrophilic conjugated polymers for sustainable fabrication of deep-red light-emitting electrochemical cells. Advanced Materials Technologies, 9(3), Article ID 2301696.
Open this publication in new window or tab >>Hydrophilic conjugated polymers for sustainable fabrication of deep-red light-emitting electrochemical cells
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2024 (English)In: Advanced Materials Technologies, E-ISSN 2365-709X, Vol. 9, no 3, article id 2301696Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2024
Keywords
aqueous-processable polymers, conjugated polymers, Hansen solubility parameters, light-emitting electrochemical cells, oligo(ethylene glycol)
National Category
Other Physics Topics Polymer Chemistry
Identifiers
urn:nbn:se:umu:diva-218034 (URN)10.1002/admt.202301696 (DOI)001115795000001 ()2-s2.0-85178893470 (Scopus ID)
Funder
Bertil & Britt Svenssons Stiftelse för Belysningsteknik, 2022 höst‐31Knut and Alice Wallenberg Foundation, WISE‐AP01‐D02Swedish Research Council, 02345Swedish Research Council, 2018–07072Swedish Research Council, 2021‐04778Swedish Energy Agency, 50779‐1Swedish Energy Agency, P2021‐00032Uppsala University
Available from: 2023-12-14 Created: 2023-12-14 Last updated: 2024-04-30Bibliographically approved
Kotewicz, K., Tang, S., Edman, L. & Wang, E. (2024). Mild and efficient extraction of fluorescent chlorophyll a from spinach leaves for application as the sustainable emitter in light-emitting electrochemical cells. ChemElectroChem, 11(5), Article ID e202300629.
Open this publication in new window or tab >>Mild and efficient extraction of fluorescent chlorophyll a from spinach leaves for application as the sustainable emitter in light-emitting electrochemical cells
2024 (English)In: ChemElectroChem, E-ISSN 2196-0216, Vol. 11, no 5, article id e202300629Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2024
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-220305 (URN)10.1002/celc.202300629 (DOI)001150555100001 ()2-s2.0-85183039063 (Scopus ID)
Funder
Swedish Research Council, 2021-04778Swedish Research Council, 2019- 02345Swedish Research Council, 2018-07072Swedish Energy Agency, P2021-00032Swedish Energy Agency, 50779-1The Swedish Foundation for International Cooperation in Research and Higher Education (STINT)Bertil & Britt Svenssons Stiftelse för Belysningsteknik, 2021höst-14Bertil & Britt Svenssons Stiftelse för Belysningsteknik, 2022höst-31Knut and Alice Wallenberg Foundation, 2022.0192
Available from: 2024-02-13 Created: 2024-02-13 Last updated: 2024-05-07Bibliographically approved
Auroux, E., Huseynova, G., Ràfols-Ribé, J., Miranda la Hera, V. & Edman, L. (2023). A metal-free and transparent light-emitting device by sequential spray-coating fabrication of all layers including PEDOT:PSS for both electrodes. RSC Advances, 13(25), 16943-16951
Open this publication in new window or tab >>A metal-free and transparent light-emitting device by sequential spray-coating fabrication of all layers including PEDOT:PSS for both electrodes
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2023 (English)In: RSC Advances, E-ISSN 2046-2069, Vol. 13, no 25, p. 16943-16951Article in journal (Refereed) Published
Abstract [en]

The concept of a metal-free and all-organic electroluminescent device is appealing from both sustainability and cost perspectives. Herein, we report the design and fabrication of such a light-emitting electrochemical cell (LEC), comprising a blend of an emissive semiconducting polymer and an ionic liquid as the active material sandwiched between two poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) conducting-polymer electrodes. In the off-state, this all-organic LEC is highly transparent, and in the on-state, it delivers uniform and fast to turn-on bright surface emission. It is notable that all three device layers were fabricated by material- and cost-efficient spray-coating under ambient air. For the electrodes, we systematically investigated and developed a large number of PEDOT:PSS formulations. We call particular attention to one such p-type doped PEDOT:PSS formulation that was demonstrated to function as the negative cathode, as well as future attempts towards all-organic LECs to carefully consider the effects of electrochemical doping of the electrode in order to achieve optimum device performance.

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2023
National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-211794 (URN)10.1039/d3ra02520a (DOI)001000925700001 ()37288374 (PubMedID)2-s2.0-85162809423 (Scopus ID)
Funder
Swedish Research Council, 2021-04778Swedish Research Council, 2019- 02345Swedish Energy Agency, 50779-1Bertil & Britt Svenssons Stiftelse för Belysningsteknik, 2022 höst-31The Kempe Foundations, SMK-1956Carl Tryggers foundation , CTS 19:86
Available from: 2023-07-12 Created: 2023-07-12 Last updated: 2023-07-12Bibliographically approved
Tang, S., Wang, Z., Xu, Y., Ma, H., Wang, J., Larsen, C., . . . Edman, L. (2023). Aggregation-induced emission by molecular design: a route to high-performance light-emitting electrochemical cells. Angewandte Chemie International Edition, 62(23), Article ID e202302874.
Open this publication in new window or tab >>Aggregation-induced emission by molecular design: a route to high-performance light-emitting electrochemical cells
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2023 (English)In: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773, Vol. 62, no 23, article id e202302874Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
Aggregation Caused Quenching, Aggregation-Induced Emission, Electrochemical Doping, Light-Emitting Electrochemical Cell, Organic Semiconductor
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-208091 (URN)10.1002/anie.202302874 (DOI)000976807100001 ()36995360 (PubMedID)2-s2.0-85153338644 (Scopus ID)
Funder
The Kempe FoundationsSwedish Research CouncilSwedish Energy AgencySwedish Foundation for Strategic ResearchWenner-Gren FoundationsBertil & Britt Svenssons Stiftelse för BelysningsteknikKnut and Alice Wallenberg Foundation
Available from: 2023-05-09 Created: 2023-05-09 Last updated: 2023-06-19Bibliographically approved
Adranno, B., Tang, S., Paterlini, V., Smetana, V., Renier, O., Bousrez, G., . . . Mudring, A.-V. (2023). Broadband white-light-emitting electrochemical cells. Advanced Photonics Research, 4(5), Article ID 2200351.
Open this publication in new window or tab >>Broadband white-light-emitting electrochemical cells
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2023 (English)In: Advanced Photonics Research, ISSN 2699-9293, Vol. 4, no 5, article id 2200351Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
emitter materials, light sources, light-emitting electrochemical cells, white light generation
National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-218963 (URN)10.1002/adpr.202200351 (DOI)000942778700001 ()
Funder
The Royal Swedish Academy of SciencesSwedish Energy Agency, 46676-1Swedish Energy Agency, 50779-1Swedish Research Council, 2021-04778Swedish Foundation for Strategic Research, EM16-0013
Available from: 2024-01-04 Created: 2024-01-04 Last updated: 2024-01-04Bibliographically approved
Huseynova, G., Ràfols-Ribé, J., Auroux, E., Huang, P., Tang, S., Larsen, C. & Edman, L. (2023). Chemical doping to control the in-situ formed doping structure in light-emitting electrochemical cells. Scientific Reports, 13(1), Article ID 11457.
Open this publication in new window or tab >>Chemical doping to control the in-situ formed doping structure in light-emitting electrochemical cells
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2023 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 13, no 1, article id 11457Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-212310 (URN)10.1038/s41598-023-38006-y (DOI)37454107 (PubMedID)2-s2.0-85164758513 (Scopus ID)
Funder
Carl Tryggers foundation The Kempe FoundationsSwedish Research CouncilSwedish Energy AgencyOlle Engkvists stiftelseBertil & Britt Svenssons Stiftelse för BelysningsteknikKnut and Alice Wallenberg Foundation
Available from: 2023-07-25 Created: 2023-07-25 Last updated: 2023-07-25Bibliographically approved
dos Santos, J. M., Chan, C.-Y., Tang, S., Hall, D., Matulaitis, T., Cordes, D. B., . . . Zysman-Colman, E. (2023). Color tuning of multi-resonant thermally activated delayed fluorescence emitters based on fully fused polycyclic amine/carbonyl frameworks. Journal of Materials Chemistry C, 11(24), 8263-8273
Open this publication in new window or tab >>Color tuning of multi-resonant thermally activated delayed fluorescence emitters based on fully fused polycyclic amine/carbonyl frameworks
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2023 (English)In: Journal of Materials Chemistry C, ISSN 2050-7526, E-ISSN 2050-7534, Vol. 11, no 24, p. 8263-8273Article in journal (Refereed) Published
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

Place, publisher, year, edition, pages
Royal Society of Chemistry, 2023
National Category
Materials Chemistry
Identifiers
urn:nbn:se:umu:diva-209301 (URN)10.1039/d3tc00641g (DOI)000986659900001 ()2-s2.0-85159346152 (Scopus ID)
Funder
Swedish Research CouncilSwedish Energy AgencyBertil & Britt Svenssons Stiftelse för Belysningsteknik
Available from: 2023-06-08 Created: 2023-06-08 Last updated: 2023-09-20Bibliographically approved
Projects
Light-emitting electrochemical cells for low-cost and ´green´ lighting and displays [2011-00584_Vinnova]; Umeå UniversityOrganisk elektronik - nanodesign för funktionella applikationer [P34145-2_Energi]; Umeå University; Publications
Enevold, J., Larsen, C., Zakrisson, J., Andersson, M. & Edman, L. (2018). Realizing large-area arrays of semiconducting fullerene nanostructures with direct laser interference patterning. Nano letters (Print), 18(1), 540-545
The light-emitting electrochemical cell: Developing rational design principles for efficient, bright and green operation [2017-04380_VR]; Umeå University; Publications
Enevold, J., Dahlberg, T., Stangner, T., Tang, S., Lindh, E. M., Gracia-Espino, E., . . . Edman, L. (2020). Tunable two-dimensional patterning of a semiconducting Nanometer-Thin C60 fullerene film using a spatial light modulator. ACS Applied Nano Materials, 3(6), 2574-0970
Sustainable and efficient light patches for future illumination [P46523-1_Energi]; Umeå University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-2495-7037

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