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Xiong, W., Tang, S., Murto, P., Zhu, W., Edman, L. & Wang, E. (2019). Combining Benzotriazole and Benzodithiophene Host Units in Host-Guest Polymers for Efficient and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells. Advanced Optical Materials, 7(15), Article ID 1900280.
Open this publication in new window or tab >>Combining Benzotriazole and Benzodithiophene Host Units in Host-Guest Polymers for Efficient and Stable Near-Infrared Emission from Light-Emitting Electrochemical Cells
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2019 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 15, article id 1900280Article in journal (Refereed) Published
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.

Keywords
conjugated polymers, host-guest copolymers, near-infrared emission light-emitting electrochemical cells
National Category
Polymer Chemistry
Identifiers
urn:nbn:se:umu:diva-162672 (URN)10.1002/adom.201900280 (DOI)000478735800007 ()
Available from: 2019-08-29 Created: 2019-08-29 Last updated: 2019-08-29Bibliographically approved
Tang, S., Murto, P., Wang, J., Larsen, C., Andersson, M. R., Wang, E. & Edman, L. (2019). 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?. Advanced Optical Materials, 7(18), Article ID 1900451.
Open this publication in new window or tab >>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?
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2019 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 18, article id 1900451Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
John Wiley & Sons, 2019
Keywords
host-guest copolymers, intramolecular energy transfer, light-emitting electrochemical cells, near-infrared emission
National Category
Materials Engineering Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-164065 (URN)10.1002/adom.201900451 (DOI)000487087400020 ()
Available from: 2019-10-15 Created: 2019-10-15 Last updated: 2019-10-15Bibliographically approved
Tang, S., Murto, P., Wang, J., Larsen, C., Andersson, M. R., Wang, E. & Edman, L. (2019). 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?. Advanced Optical Materials, 7(18), Article ID 1900451.
Open this publication in new window or tab >>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?
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2019 (English)In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 7, no 18, article id 1900451Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Wiley-VCH Verlagsgesellschaft, 2019
Keywords
host-guest copolymers, intramolecular energy transfer, light-emitting electrochemical cells, near- infrared emission
National Category
Atom and Molecular Physics and Optics Polymer Chemistry
Identifiers
urn:nbn:se:umu:diva-164143 (URN)10.1002/adom.201900451 (DOI)000487087400020 ()
Available from: 2019-10-17 Created: 2019-10-17 Last updated: 2019-10-17Bibliographically approved
Jin, X., Sandström, A., Lindh, E. M., Yang, W., Tang, S. & Edman, L. (2018). Challenging conventional wisdom: finding high-performance electrodes for light-emitting electrochemical cells. ACS Applied Materials and Interfaces, 10(39), 33380-33389
Open this publication in new window or tab >>Challenging conventional wisdom: finding high-performance electrodes for light-emitting electrochemical cells
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2018 (English)In: ACS Applied Materials and Interfaces, ISSN 1944-8244, E-ISSN 1944-8252, Vol. 10, no 39, p. 33380-33389Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
air-stable electrode, injection barrier, light-emitting electrochemical cell, electrochemical stability, reflectance
National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:umu:diva-152982 (URN)10.1021/acsami.8b13036 (DOI)000446919800049 ()30199215 (PubMedID)
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilSwedish Energy AgencyThe Kempe Foundations
Available from: 2018-11-01 Created: 2018-11-01 Last updated: 2018-11-01Bibliographically approved
Murto, P., Tang, S., Larsen, C., Xu, X., Sandström, A., Pietarinen, J., . . . Edman, L. (2018). Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell. ACS Applied Energy Materials, 1(4), 1753-1761
Open this publication in new window or tab >>Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell
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2018 (English)In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 4, p. 1753-1761Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
near-infrared, NIR, large-area device, light-emitting electrochemical cell, LEC, copolymer, solution processing
Identifiers
urn:nbn:se:umu:diva-157352 (URN)10.1021/acsaem.8b00283 (DOI)000458705400044 ()
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilSwedish Energy AgencySwedish Research Council Formas
Available from: 2019-03-15 Created: 2019-03-15 Last updated: 2019-03-15Bibliographically approved
Murto, P., Tang, S., Larsen, C., Xu, X., Sandström, A., Pietarinen, J., . . . Edman, L. (2018). Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell. ACS Applied Energy Materials, 1(4), 1753-1761
Open this publication in new window or tab >>Incorporation of Designed Donor-Acceptor-Donor Segments in a Host Polymer for Strong Near-Infrared Emission from a Large-Area Light-Emitting Electrochemical Cell
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2018 (English)In: ACS Applied Energy Materials, ISSN 2574-0962, Vol. 1, no 4, p. 1753-1761Article in journal (Refereed) Published
Abstract [en]

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

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2018
Keywords
near-infrared, NIR, large-area device, light-emitting electrochemical cell, LEC, copolymer, solution processing
National Category
Polymer Chemistry Other Chemistry Topics
Identifiers
urn:nbn:se:umu:diva-156904 (URN)10.1021/acsaem.8b00283 (DOI)000458705400044 ()
Available from: 2019-04-16 Created: 2019-04-16 Last updated: 2019-04-16Bibliographically approved
Mindemark, J., Tang, S., Li, H. & Edman, L. (2018). Ion Transport beyond the Polyether Paradigm: Introducing Oligocarbonate Ion Transporters for Efficient Light-Emitting Electrochemical Cells. Advanced Functional Materials, 28(32), Article ID 1801295.
Open this publication in new window or tab >>Ion Transport beyond the Polyether Paradigm: Introducing Oligocarbonate Ion Transporters for Efficient Light-Emitting Electrochemical Cells
2018 (English)In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 32, article id 1801295Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
WILEY-V C H VERLAG GMBH, 2018
Keywords
light emission, organic electronics, phase separation, polycarbonates, polymer electrolytes
National Category
Inorganic Chemistry
Identifiers
urn:nbn:se:umu:diva-151048 (URN)10.1002/adfm.201801295 (DOI)000440810500004 ()
Available from: 2018-09-05 Created: 2018-09-05 Last updated: 2018-09-05Bibliographically 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
Tang, S., Murto, P., Xu, X., Larsen, C., Wang, E. & Edman, L. (2017). 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 Emitter. Chemistry of Materials, 29(18), 7750-7759
Open this publication in new window or tab >>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 Emitter
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2017 (English)In: Chemistry of Materials, ISSN 0897-4756, E-ISSN 1520-5002, Vol. 29, no 18, p. 7750-7759Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
AMER CHEMICAL SOC, 2017
National Category
Other Chemistry Topics
Identifiers
urn:nbn:se:umu:diva-140905 (URN)10.1021/acs.chemmater.7b02049 (DOI)000411918900016 ()
Available from: 2017-11-16 Created: 2017-11-16 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
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ORCID iD: ORCID iD iconorcid.org/0000-0003-1274-5918

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