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Spraying Light: Ambient-Air Fabrication of Large-Area Emissive Devices on Complex-Shaped Surfaces
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
Umeå University, Faculty of Science and Technology, Department of Physics.
2014 (English)In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 29, p. 4975-4980Article in journal (Refereed) Published
Abstract [en]

Light-emitting electrochemical cells, featuring uniform and efficient light emission over areas of 200 cm(2), are fabricated under ambient air with a for-the-purpose developed "spray-sintering" process. This fault-tolerant fabrication technique can also produce multicolored emission patterns via sequential deposition of different inks based on identical solvents. Significantly, additive spray-sintering using a mobile airbrush allows a straightforward addition of emissive function onto a wide variety of complex-shaped surfaces, as exemplified by the realization of a light-emitting kitchenware fork.

Place, publisher, year, edition, pages
2014. Vol. 26, no 29, p. 4975-4980
Keywords [en]
large-area light emission, complex surfaces, solution-based processing, ambient fabrication, light-emitting electrochemical cell
National Category
Atom and Molecular Physics and Optics
Identifiers
URN: urn:nbn:se:umu:diva-93224DOI: 10.1002/adma.201401286ISI: 000340500700011OAI: oai:DiVA.org:umu-93224DiVA, id: diva2:774279
Part of project
Large-area light-emission on the roll, Swedish Foundation for Strategic Research Available from: 2014-12-22 Created: 2014-09-15 Last updated: 2019-12-18Bibliographically approved
In thesis
1. Functional and Flexible Light-Emitting Electrochemical Cells
Open this publication in new window or tab >>Functional and Flexible Light-Emitting Electrochemical Cells
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The introduction of artificial illumination has brought extensive benefits to mankind, and during the last years we have seen a tremendous progress in this field with the introduction of the energy-efficient light-emitting diode (LED) and the high-contrast organic LED display. These high-end technologies are, however, produced using costly and complex processes, and it is anticipated that the next big thing in the field will be the advent of a low-cost and “green” illumination technology, which can be fabricated in a cost- and material-efficient manner using non-toxic and abundant raw materials, and which features attractive form factors such as flexibility, robustness and light-weight. The light-emitting electrochemical cell (LEC) is a newly invented illumination technology, and in this thesis we present results that imply that it can turn the above vision into reality.

The thin-film LEC comprises an active material sandwiched between a cathode and an anode as its key constituent parts. With the aid of a handheld air-brush, we show that functional large-area LECs can be fabricated by simply spraying three layers of solution -- forming the anode, active material, and cathode -- on top of a substrate. We also demonstrate that such “spray-sintered” LECs can feature multicolored emission patterns, and be fabricated directly on complex-shaped surfaces, with one notable example being the realization of a light-emission fork!

Almost all LECs up-to-date have been fabricated on glass substrates, but for a flexible and light-weight emissive device, it is obviously relevant to identify more appropriate substrate materials. For this end, we show that it is possible to spray-coat the entire LEC directly on conventional copy paper, and that such paper-LECs feature uniform light-emission even under heavy bending and flexing.

We have further looked into the fundamental aspects of the LEC operation and demonstrated that the in-situ doping formation, which is a characteristic and heralded feature of LECs, can bring problems in the form of doping-induced self-absorption. By quantitatively analyzing this phenomenon, we provided straightforward guidelines on how future efficiency-optimized LEC devices should be designed.

The in-situ doping formation process brings the important advantage that LECs can be fabricated from solely air-stabile materials, but during light emission the device needs to be protected from the ambient air. We have therefore developed a functional glass/epoxy encapsulation procedure for the attainment of LEC devices that feature a record-long ambient-air operational lifetime of 5600 h. For the light-emission device of the future, it is however critical that the encapsulation is flexible, and in our last study, we show that the use of multi-layer barrier can result in high-performance flexible LECs.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2015. p. 57
Keywords
all-ambient fabrication, ambient-air lifetime, encapsulation, flexible, light-emitting electrochemical cells, light-emitting paper
National Category
Nano Technology Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-102400 (URN)978-91-7601-257-4 (ISBN)
Public defence
2015-05-22, N300, Naturvetarhuset, Umeå University, Umeå, 10:00 (English)
Opponent
Supervisors
Available from: 2015-04-30 Created: 2015-04-23 Last updated: 2018-06-07Bibliographically approved
2. Structure and morphology control of organic semiconductors for functional optoelectronic applications
Open this publication in new window or tab >>Structure and morphology control of organic semiconductors for functional optoelectronic applications
2019 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The functionality and application of organic semiconductors are largely dependent on their constituent structure and morphology. This thesis presents a number of functional and novel approaches for the control and tuning of structural and morphological features of a variety of organic semiconductor materials, and also demonstrates that these approaches can be utilized for improved device operation of field-effect transistors, organic solar cells and light-emitting electrochemical cells.

The fullerene family is a particular group of closed-cage organic semiconductors, which can be photochemically coupled into larger dimeric or polymeric structures through the excitation of the fullerene molecules by light emission. In Paper I, we perform a detailed experimental and analytical investigation, which demonstrates that this photochemical monomer-to-dimer transformation requires that both constituent fullerene molecules are photoexcited. The direct consequence is that the initial probability for the photochemical transformation is dependent on the square of the light-emission intensity.

The photochemical coupling of fullerene molecules commonly results in a distinctly lowered solubility in common hydrophobic solvents, which can be utilized for the direct patterning of fullerene films by resist-free lithography. In Paper II, we utilize this patterning opportunity for the fabrication of one-dimensional fullerene nano-stripes using two-beam laser interference lithography. A desired high contrast between the patterned and non-patterned fullerene regions is facilitated by the non-linear response of the photochemical transformation process, as predicted by the findings in Paper I. The patterned fullerene nano-stripes were utilized as the active material in field-effect transistors, which featured high electron mobility and large on-off ratio.

This patterning was in Paper III extended into easy tunable two-dimensional fullerene structures by the design and development of an exposure setup, essentially comprising a laser and a spatial light modulator featuring >8 millions of independently controlled mirrors. With this approach, we could fabricate well-defined fullerene microdots over a several square-millimeter sized area, which was utilized as an internal out-coupling layer in a light-emitting electrochemical cell with significantly enhanced light output.

Paper IV reports on the development of a new “spray-sintering” method for the cost-efficient solution-based deposition of the active material in light-emitting electrochemical cells. This carefully designed approach effectively resolves the issue with phase separation between the hydrophobic organic semiconductor and the hydrophilic electrolyte that results in a sub-par LEC performance, and also allows for the direct fabrication of LEC devices onto complex surfaces, including a stainless-steel fork.

Paper V finally reports on the design and synthesis of a soluble small molecule, featuring a donor-acceptor-donor configuration. It acts as the donor when combined with a soluble fullerene acceptor in the active material of organic solar cells, and such devices with optimized donor/acceptor nanomorphology feature a high open-circuit voltage of ~1.0 V during solar illumination.

Place, publisher, year, edition, pages
Umeå: Umeå University, 2019. p. 65
Keywords
Organic electronics, organic photonics, patterning, fullerene, polymerization, dimerization, spray-deposition, morphology, small molecule donor, high open-circuit voltage
National Category
Polymer Technologies Nano Technology Other Physics Topics Condensed Matter Physics
Identifiers
urn:nbn:se:umu:diva-166407 (URN)978-91-7855-170-5 (ISBN)978-91-7855-169-9 (ISBN)
Public defence
2020-01-09, Bio.A.206, Biologihuset, Umeå, 09:00 (English)
Opponent
Supervisors
Available from: 2019-12-19 Created: 2019-12-16 Last updated: 2019-12-17Bibliographically approved

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Sandström, AndreasAsadpoordarvish, AmirEnevold, JennyEdman, Ludvig

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