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Publications (10 of 35) Show all publications
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
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
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
Ràfols-Ribé, J., Hänisch, C., Larsen, C., Reineke, S. & Edman, L. (2023). In situ determination of the orientation of the emissive dipoles in light-emitting electrochemical cells. Advanced Materials Technologies, 8(13), Article ID 2202120.
Open this publication in new window or tab >>In situ determination of the orientation of the emissive dipoles in light-emitting electrochemical cells
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2023 (English)In: Advanced Materials Technologies, E-ISSN 2365-709X, Vol. 8, no 13, article id 2202120Article in journal (Refereed) Published
Abstract [en]

The orientation of the emissive dipoles in thin-film devices is important since it strongly affects the light outcoupling and thereby the device emission efficiency. The light-emitting electrochemical cell (LEC) is particularly interesting in this context because its emissive dipoles are located in a high electric-field p-n junction, which is formed in situ by redistribution of bulky ions. This implies that the dipole orientation could be distinctly different in the driven LEC compared to the pristine device. This study develops the destructive-interference microcavity method for the accurate in situ determination of the orientation of the emissive dipoles during LEC operation and apply it on a common LEC device comprising an amorphous conjugated polymer termed Super Yellow as the emitter. It is found that ≈95% of the emissive dipoles are oriented in the horizontal direction with respect to the thin-film plane in both the pristine LEC and during steady-state light emission. This finding is attractive since it enables for efficient outcoupling of the generated photons, and interesting because it shows that a horizontal orientation of the emissive dipoles can remain despite the existence of a strong perpendicular electric field and the nearby motion of bulky ions during LEC operation.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
anisotropy, device efficiency, dipole orientation, light-emitting electrochemical cells, Super Yellow
National Category
Atom and Molecular Physics and Optics Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-206790 (URN)10.1002/admt.202202120 (DOI)000963273400001 ()2-s2.0-85151955762 (Scopus ID)
Funder
The Kempe FoundationsSwedish Research CouncilSwedish Energy AgencyOlle Engkvists stiftelseWenner-Gren FoundationsBertil & Britt Svenssons Stiftelse för Belysningsteknik
Available from: 2023-04-24 Created: 2023-04-24 Last updated: 2023-11-03Bibliographically approved
Ràfols-Ribé, J., Zhang, X., Larsen, C., Lundberg, P., Lindh, E. M., Mai, C. T., . . . Edman, L. (2022). Controlling the emission zone by additives for improved light‐emitting electrochemical cells. Advanced Materials, 34(8), Article ID 2107849.
Open this publication in new window or tab >>Controlling the emission zone by additives for improved light‐emitting electrochemical cells
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2022 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 34, no 8, article id 2107849Article in journal (Refereed) Published
Abstract [en]

The position of the emission zone (EZ) in the active material of a light-emitting electrochemical cell (LEC) has a profound influence on its performance because of microcavity effects and doping- and electrode-induced quenching. Previous attempts of EZ control have focused on the two principal constituents in the active material—the organic semiconductor (OSC) and the mobile ions—but this study demonstrates that it is possible to effectively control the EZ position through the inclusion of an appropriate additive into the active material. More specifically, it is shown that a mere modification of the end group on an added neutral compound, which also functions as an ion transporter, results in a shifted EZ from close to the anode to the center of the active material, which translates into a 60% improvement of the power efficiency. This particular finding is rationalized by a lowering of the effective electron mobility of the OSC through specific additive: OSC interactions, but the more important generic conclusion is that it is possible to control the EZ position, and thereby the LEC performance, by the straightforward inclusion of an easily tuned additive in the active material.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2022
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-201531 (URN)10.1002/adma.202107849 (DOI)000742703700001 ()34891219 (PubMedID)2-s2.0-85122826739 (Scopus ID)
Funder
The Kempe FoundationsSwedish Research CouncilSwedish Energy AgencySwedish Foundation for Strategic ResearchOlle Engkvists stiftelseWenner-Gren FoundationsBertil & Britt Svenssons Stiftelse för Belysningsteknik
Available from: 2022-12-07 Created: 2022-12-07 Last updated: 2022-12-07Bibliographically approved
Larsen, C., Lundberg, P., Tang, S., Ràfols-Ribé, J., Sandström, A., Lindh, E. M., . . . Edman, L. (2021). A tool for identifying green solvents for printed electronics. Nature Communications, 12, Article ID 4510.
Open this publication in new window or tab >>A tool for identifying green solvents for printed electronics
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2021 (English)In: Nature Communications, E-ISSN 2041-1723, Vol. 12, article id 4510Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Nature research, 2021
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-170536 (URN)10.1038/s41467-021-24761-x (DOI)000680504900010 ()34301943 (PubMedID)2-s2.0-85111109535 (Scopus ID)
Note

Originally included in thesis in manuscript form.

Available from: 2020-05-07 Created: 2020-05-07 Last updated: 2023-03-28Bibliographically approved
Tang, S., Larsen, C., Ràfols-Ribé, J., Wang, J. & Edman, L. (2021). An Amorphous Spirobifluorene-Phosphine-Oxide Compound as the Balanced n-Type Host in Bright and Efficient Light-Emitting Electrochemical Cells with Improved Stability. Advanced Optical Materials, 9(7), Article ID 2002105.
Open this publication in new window or tab >>An Amorphous Spirobifluorene-Phosphine-Oxide Compound as the Balanced n-Type Host in Bright and Efficient Light-Emitting Electrochemical Cells with Improved Stability
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2021 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 9, no 7, article id 2002105Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2021
Keywords
high efficiency, improved lifetime, light-emitting electrochemical cells, strong luminance, thermal properties
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-180652 (URN)10.1002/adom.202002105 (DOI)000611087100001 ()2-s2.0-85099749514 (Scopus ID)
Available from: 2021-02-24 Created: 2021-02-24 Last updated: 2023-03-24Bibliographically approved
Ràfols-Ribé, J., Gracia-Espino, E., Jenatsch, S., Lundberg, P., Sandström, A., Tang, S., . . . Edman, L. (2021). Elucidating Deviating Temperature Behavior of Organic Light-Emitting Diodes and Light-Emitting Electrochemical Cells. Advanced Optical Materials, 9(1), Article ID 2001405.
Open this publication in new window or tab >>Elucidating Deviating Temperature Behavior of Organic Light-Emitting Diodes and Light-Emitting Electrochemical Cells
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2021 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 9, no 1, article id 2001405Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2021
Keywords
doping effects, emission zone position, light-emitting electrochemical cells, optical simulation, organic light-emitting diodes, Super Yellow, temperature dependence
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-177163 (URN)10.1002/adom.202001405 (DOI)000588678900001 ()2-s2.0-85096640158 (Scopus ID)
Available from: 2020-12-08 Created: 2020-12-08 Last updated: 2023-03-24Bibliographically approved
Auroux, E., Sandström, A., Larsen, C., Zäll, E., Lundberg, P., Wågberg, T. & Edman, L. (2021). Evidence and Effects of Ion Transfer at Active-Material/Electrode Interfaces in Solution-Fabricated Light-Emitting Electrochemical Cells. Advanced Electronic Materials, 7(8), Article ID 2100253.
Open this publication in new window or tab >>Evidence and Effects of Ion Transfer at Active-Material/Electrode Interfaces in Solution-Fabricated Light-Emitting Electrochemical Cells
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2021 (English)In: Advanced Electronic Materials, E-ISSN 2199-160X, Vol. 7, no 8, article id 2100253Article in journal (Refereed) Published
Abstract [en]

The light-emitting electrochemical cell (LEC) allows for energy- and cost-efficient printing and coating fabrication of its entire device structure, including both electrodes and the single-layer active material. This attractive fabrication opportunity is enabled by the electrochemical action of mobile ions in the active material. However, a related and up to now overlooked issue is that such solution-fabricated LECs commonly comprise electrode/active-material interfaces that are open for transfer of the mobile ions, and it is herein demonstrated that a majority of the mobile anions in a common spray-coated active material can transfer into a spray-coated poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) positive electrode during LEC operation. Since it is well established that the mobile ion concentration in the active material has a profound influence on the LEC performance, this significant ion transfer is an important factor that should be considered in the design of low-cost LEC devices that deliver high performance.

Place, publisher, year, edition, pages
Wiley-Blackwell Publishing Inc., 2021
Keywords
active-material design, electrode electrochemistry, ion transfer, light-emitting electrochemical cell, PEDOT:PSS, solution fabrication
National Category
Materials Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-185329 (URN)10.1002/aelm.202100253 (DOI)000662108100001 ()2-s2.0-85108074845 (Scopus ID)
Funder
Carl Tryggers foundation The Kempe FoundationsOlle Engkvists stiftelseInterreg NordBertil & Britt Svenssons Stiftelse för BelysningsteknikSwedish Research CouncilSwedish Energy AgencyRegion Västerbotten
Available from: 2021-06-28 Created: 2021-06-28 Last updated: 2023-03-31Bibliographically approved
Liu, Y.-f., Tang, S., Fan, J., Gracia-Espino, E., Yang, J., Liu, X., . . . Wang, J. (2021). Highly Soluble CsPbBr3 Perovskite Quantum Dots for Solution-Processed Light-Emission Devices. ACS Applied Nano Materials, 1162-1174
Open this publication in new window or tab >>Highly Soluble CsPbBr3 Perovskite Quantum Dots for Solution-Processed Light-Emission Devices
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2021 (English)In: ACS Applied Nano Materials, E-ISSN 2574-0970, p. 1162-1174Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2021
Keywords
perovskite quantum dots, surface ligands, high solubility, good film forming capacity, light-emitting electrochemical cell, ion migration
National Category
Natural Sciences
Research subject
Materials Science
Identifiers
urn:nbn:se:umu:diva-179020 (URN)10.1021/acsanm.0c02797 (DOI)000624546800025 ()2-s2.0-85100019584 (Scopus ID)
Funder
Swedish Energy Agency, 45419-1Swedish Energy Agency, 46523-1Swedish Energy Agency, 50779-1The Kempe FoundationsSwedish Research Council, 2017-04380Swedish Research Council, 2017-04862Swedish Research Council, 2018-03937Swedish Research Council, 2019-02345Swedish Foundation for Strategic Research Stiftelsen Olle Engkvist Byggmästare, 186-0637Stiftelsen Olle Engkvist Byggmästare, 193-0578
Available from: 2021-01-22 Created: 2021-01-22 Last updated: 2021-07-02Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0002-2480-3786

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