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Lindh, E. M., Lundberg, P., Lanz, T. & Edman, L. (2019). Optical analysis of light-emitting electrochemical cells. Scientific Reports, 9, Article ID 10433.
Open this publication in new window or tab >>Optical analysis of light-emitting electrochemical cells
2019 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 9, article id 10433Article in journal (Refereed) Published
Abstract [en]

The light-emitting electrochemical cell (LEC) is a contender for emerging applications of light, primarily because it offers low-cost solution fabrication of easily functionalized device architectures. The attractive properties originate in the in-situ formation of electrochemically doped transport regions that enclose an emissive intrinsic region, but the understanding of how this intricate doping structure affects the optical performance of the LEC is largely lacking. We combine angle- and doping-dependent measurements and simulations, and demonstrate that the emission zone in our high-performance LEC is centered at ~30% of the active-layer thickness (dal) from the anode. We further find that the emission intensity and efficiency are undulating with dal, and establish that the first emission maximum at dal ~ 100 nm is largely limited by the lossy coupling of excitons to the doping regions, whereas the most prominent loss channel at the second maximum at dal ~ 300 nm is wave-guided modes.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Nano Technology Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-156092 (URN)10.1038/s41598-019-46860-y (DOI)000475845400037 ()31320711 (PubMedID)2-s2.0-85069470003 (Scopus ID)
Note

Originally included in thesis in manuscript form.

Available from: 2019-02-05 Created: 2019-02-05 Last updated: 2019-08-08Bibliographically approved
Lundberg, P., Tsuchiya, Y., Lindh, E. M., Tang, S., Adachi, C. & Edman, L. (2019). Thermally activated delayed fluorescence with 7% external quantum efficiency from a light-emitting electrochemical cell. Nature Communications, 10, Article ID 5307.
Open this publication in new window or tab >>Thermally activated delayed fluorescence with 7% external quantum efficiency from a light-emitting electrochemical cell
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 5307Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-166389 (URN)10.1038/s41467-019-13289-w (DOI)000498195100005 ()31757959 (PubMedID)2-s2.0-85075497295 (Scopus ID)
Available from: 2019-12-17 Created: 2019-12-17 Last updated: 2020-04-03Bibliographically approved
Dahlberg, T., Stangner, T., Hanqing, Z., Wiklund, K., Lundberg, P., Edman, L. & Andersson, M. (2018). 3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers. Scientific Reports, 8(1), Article ID 3372.
Open this publication in new window or tab >>3D printed water-soluble scaffolds for rapid production of PDMS micro-fluidic flow chambers
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, no 1, article id 3372Article in journal (Refereed) Published
Abstract [en]

We report a novel method for fabrication of three-dimensional (3D) biocompatible micro-fluidic flow chambers in polydimethylsiloxane (PDMS) by 3D-printing water-soluble polyvinyl alcohol (PVA) filaments as master scaffolds. The scaffolds are first embedded in the PDMS and later residue-free dissolved in water leaving an inscription of the scaffolds in the hardened PDMS. We demonstrate the strength of our method using a regular, cheap 3D printer, and evaluate the inscription process and the channels micro-fluidic properties using image analysis and digital holographic microscopy. Furthermore, we provide a protocol that allows for direct printing on coverslips and we show that flow chambers with a channel cross section down to 40 x 300 μm can be realized within 60 min. These flow channels are perfectly transparent, biocompatible and can be used for microscopic applications without further treatment. Our proposed protocols facilitate an easy, fast and adaptable production of micro-fluidic channel designs that are cost-effective, do not require specialized training and can be used for a variety of cell and bacterial assays. To help readers reproduce our micro-fluidic devices, we provide: full preparation protocols, 3D-printing CAD files for channel scaffolds and our custom-made molding device, 3D printer build-plate leveling instructions, and G-code.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Other Materials Engineering Other Engineering and Technologies not elsewhere specified Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-144631 (URN)10.1038/s41598-018-21638-w (DOI)000425500300044 ()
Funder
Swedish Research Council, 2013-5379The Kempe Foundations, JCK-1622
Available from: 2018-02-08 Created: 2018-02-08 Last updated: 2018-08-16Bibliographically approved
Lindh, E. M., Lundberg, P., Lanz, T., Mindemark, J. & Edman, L. (2018). The Weak Microcavity as an Enabler for Bright and Fault-tolerant Light-emitting Electrochemical Cells. Scientific Reports, 8, Article ID 6970.
Open this publication in new window or tab >>The Weak Microcavity as an Enabler for Bright and Fault-tolerant Light-emitting Electrochemical Cells
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2018 (English)In: Scientific Reports, ISSN 2045-2322, E-ISSN 2045-2322, Vol. 8, article id 6970Article in journal (Refereed) Published
Abstract [en]

The light-emitting electrochemical cell (LEC) is functional at substantial active-layer thickness, and is as such heralded for being fit for low-cost and fault-tolerant solution-based fabrication. We report here that this statement should be moderated, and that in order to obtain a strong luminous output, it is fundamentally important to fabricate LEC devices with a designed thickness of the active layer. By systematic experimentation and simulation, we demonstrate that weak optical microcavity effects are prominent in a common LEC system, and that the luminance and efficiency, as well as the emission color and the angular intensity, vary in a periodic manner with the active-layer thickness. Importantly, we demonstrate that high-performance light-emission can be attained from LEC devices with a significant active-layer thickness of 300 nm, which implies that low-cost solution-processed LECs are indeed a realistic option, provided that the device structure has been appropriately designed from an optical perspective.

Place, publisher, year, edition, pages
Nature Publishing Group, 2018
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-147802 (URN)10.1038/s41598-018-25287-x (DOI)000431291500022 ()29725061 (PubMedID)
Note

Publisher Correction: M. Lindh, P. Lundberg, T. Lanz, J. Mindemark, L. Edman. The Weak Microcavity as an Enabler for Bright and Fault-tolerant Light-emitting Electrochemical Cells. Scientific Reports. 2018;8 DOI: 10.1038/s41598-018-26760-3

Available from: 2018-05-22 Created: 2018-05-22 Last updated: 2019-02-05Bibliographically approved
Tang, S., Sandström, A., Lundberg, P., Lanz, T., Larsen, C., van Reenen, S., . . . Edman, L. (2017). Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency. Nature Communications, 8, Article ID 1190.
Open this publication in new window or tab >>Design rules for light-emitting electrochemical cells delivering bright luminance at 27.5 percent external quantum efficiency
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2017 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 8, article id 1190Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Nature Publishing Group, 2017
National Category
Other Physics Topics Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-141807 (URN)10.1038/s41467-017-01339-0 (DOI)000413894100012 ()29085078 (PubMedID)
Available from: 2017-11-27 Created: 2017-11-27 Last updated: 2018-06-09Bibliographically approved
Lundberg, P., Lindh, M., Tang, S. & Edman, L. (2017). Toward Efficient and Metal-Free Emissive Devices: A Solution Processed Host Guest Light-Emitting Electrochemical Cell Featuring Thermally Activated Delayed Fluorescence. ACS Applied Materials and Interfaces, 9(34), 28810-28816
Open this publication in new window or tab >>Toward Efficient and Metal-Free Emissive Devices: A Solution Processed Host Guest Light-Emitting Electrochemical Cell Featuring Thermally Activated Delayed Fluorescence
2017 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 9, no 34, p. 28810-28816Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
Keywords
light-emitting electrochemical cell, thermally activated delayed fluorescence, low-cost solution ocessing. efficient and metal-free emitter, sustainable illumination technology, XTER DL, 1953, JOURNAL OF CHEMICAL PHYSICS, V21, P836 erster Theodor, 2012, JOURNAL OF BIOMEDICAL OPTICS, V17, leur B., 2013, Molecular Fluorescence, iend RH, 1999, NATURE, V397, P121 tyba Piotr, 2011, ACS NANO, V5, P574 ng Zhehan, 2015, ECONOMIC GEOLOGY, V110, P1925
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-140478 (URN)10.1021/acsami.7b07826 (DOI)000409395500075 ()28762717 (PubMedID)
Available from: 2017-10-23 Created: 2017-10-23 Last updated: 2018-06-09Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0003-3481-5163

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