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Sandström, Andreas
Publications (10 of 16) Show all publications
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 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
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
Asadpoordarvish, A., Sandström, A. & Edman, L. (2016). A Flexible Encapsulation Structure for Ambient-Air Operation of Light-Emitting Electrochemical Cells. Advanced Engineering Materials, 18(1), 105-110
Open this publication in new window or tab >>A Flexible Encapsulation Structure for Ambient-Air Operation of Light-Emitting Electrochemical Cells
2016 (English)In: Advanced Engineering Materials, ISSN 1438-1656, E-ISSN 1527-2648, Vol. 18, no 1, p. 105-110Article in journal (Other academic) Published
Abstract [en]

The emerging field of organic electronics is heralded because it promises low-cost and flexible devices, and it was recently demonstrated that a light-emitting electrochemical cell (LEC) can be fabricated with cost-efficient methods under ambient air. However, the LEC turns sensitive to oxygen and water during light-emission, and it is therefore timely to identify flexible encapsulation structures. Here, we demonstrate that a multilayer film, featuring a water and oxygen barrier property of ≈1 × 10–3 g/m2/day and ≈1 × 10–3 cm3/m2/bar/day respectively, is fit for this task. By sandwiching an LEC between such multilayer barriers, as attached by a UV-curable epoxy, we realize flexible LECs with performance on par with identical glass-encapsulated devices, and which remain functional after one year storage under air.

National Category
Nano Technology
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-102398 (URN)10.1002/adem.201500245 (DOI)000370146000014 ()
Note

Originally included in thesis in manuscript form.

Available from: 2015-04-23 Created: 2015-04-23 Last updated: 2018-06-07Bibliographically approved
Lanz, T., Sandström, A., Tang, S., Chabrecek, P., Sonderegger, U. & Edman, L. (2016). A light–emission textile device: conformal spray-sintering of a woven fabric electrode. Flexible and Printed Electronics, 1(2), Article ID 025004.
Open this publication in new window or tab >>A light–emission textile device: conformal spray-sintering of a woven fabric electrode
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2016 (English)In: Flexible and Printed Electronics, ISSN 2058-8585, Vol. 1, no 2, article id 025004Article in journal (Refereed) Published
Abstract [en]

We report on the realization of an ultra-flexible, light-weight and large-area emissive textile device. The anode and active material of a light-emitting electrochemical cell (LEC) were deposited by conformal spray-coating of a transparent fabric-based electrode, comprising a weave of fine Ag-coated Cu wires and poly(ethylene naphthalene) monofilament fibers embedded in a polyurethane matrix. The yellow-emitting textile featured low turn-on voltage (5 V), high maximum brightness (>4000 cd m−2), good efficiency (3.4 cd A−1), and reasonable lifetime (180 h at >100 cd m−2). Uniform emission to the eye was attained from thin and highly flexible textiles featuring a large emission area of 42 cm2, without resorting to planarization of the partially wavy-shaped (valley-to-peak height = 2.7 μm) fabric electrode. The key enabling factors for the functional emissive textile are the characteristic in situ electrochemical doping of LEC devices, the 'dry' spray-sintering deposition of the active material, and the attractive mechanical, electronic and optical properties of the fabric-based electrode.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
National Category
Textile, Rubber and Polymeric Materials Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:umu:diva-124284 (URN)10.1088/2058-8585/1/2/025004 (DOI)000399176000006 ()
Available from: 2016-08-01 Created: 2016-08-01 Last updated: 2018-06-07Bibliographically approved
Lindh, E. M., Sandström, A., Andersson, M. R. & Edman, L. (2016). Luminescent line art by direct-write patterning. Light: Science & Applications, 5, Article ID e16050.
Open this publication in new window or tab >>Luminescent line art by direct-write patterning
2016 (English)In: Light: Science & Applications, ISSN 2047-7538, Vol. 5, article id e16050Article in journal (Refereed) Published
Abstract [en]

We present a direct-write patterning method for the realization of electroluminescent (EL) line art using a surface-emissive light-emitting electrochemical cell with its electrolyte and EL material separated into a bilayer structure. The line-art emission isachieved through subtractive patterning of the electrolyte layer with a stylus, and the single-step patterning can be either manual for personalization and uniqueness or automated for high throughput and repeatability. We demonstrate that the light emission is effectuated by cation-assisted electron injection in the patterned regions and that the resulting emissive lines can be as narrow as a few micrometers. The versatility of the method is demonstrated through the attainment of a wide range of light-emission patterns and colors using a variety of different materials. We propose that this low-voltage-driven and easy-to-modify luminescent line-art technology could be of interest for emerging applications, such as active packaging and personalized gadgets.

Place, publisher, year, edition, pages
Nature Publishing Group, 2016
Keywords
direct-write patterning, light-emitting electrochemical cell, luminescent line art, organic electronics
National Category
Other Physics Topics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-114168 (URN)10.1038/lsa.2016.50 (DOI)000374463100006 ()
Funder
Knut and Alice Wallenberg FoundationThe Kempe FoundationsÅForsk (Ångpanneföreningen's Foundation for Research and Development)Swedish Energy AgencySwedish Research CouncilSwedish Foundation for Strategic Research
Available from: 2016-01-15 Created: 2016-01-15 Last updated: 2019-02-05Bibliographically approved
Sandström, A. & Edman, L. (2015). Towards High-Throughput Coating and Printing of Light-Emitting Electrochemical Cells: A Review and Cost Analysis of Current and Future Methods. Energy Technology, 3(4), 329-339
Open this publication in new window or tab >>Towards High-Throughput Coating and Printing of Light-Emitting Electrochemical Cells: A Review and Cost Analysis of Current and Future Methods
2015 (English)In: Energy Technology, ISSN 2194-4288, Vol. 3, no 4, p. 329-339Article, review/survey (Refereed) Published
Abstract [en]

A revolution is ongoing in the field of artificial light emission, with two prime examples being the quickly growing application of the energy-efficient light-emitting diode (LED) in illumination and the introduction of the high-contrast organic LED (OLED) display in various handheld appliances. It is anticipated that the next big breakthrough will constitute the emergence of a true low-cost technology, which features novel and attractive form factors such as flexibility, light-weight, and large-area emission. To realize this challenging vision, it is mandatory to identify an emissive technology that can be fabricated in a low-energy and material-conservative manner. In this context, recent demonstrations of a roll-to-roll (R2R) compatible coating and printing of thin-film light-emitting electrochemical cells (LECs) on flexible substrates are highly interesting. Here, we review these achievements, and perform a first analysis of the merits of different LEC fabrication methods with regard to material consumption, capital investment, running cost, and throughput. Among our findings we mention a fault-tolerant, small-volume batch fabrication of LEC devices using spray sintering, which can be executed at a low installment cost of 100000Euro, but where the large-area devices currently carry a fabrication cost tag of 14000Eurom(-2). The true appeal of the technology is, therefore, better visualized in the high-volume R2R-coating scenario, for which the installment cost is 20times higher, but where the projected price tag is much more attractive (11Euro per m(2)). If such flexible and light-weight (and potentially metal-free) sheets are driven at a luminance of 1000cdm(-2), the cost per lumen is a mere 0.0036Eurolm(-1), which is one order of magnitude lower than the projected future costs for LEDs and OLEDs.

Keywords
cost analysis, fabrication, light-emitting electrochemical cell, R2R processing, slot-die coating
National Category
Other Physics Topics
Identifiers
urn:nbn:se:umu:diva-103737 (URN)10.1002/ente.201402201 (DOI)000353561000004 ()
Available from: 2015-06-08 Created: 2015-05-28 Last updated: 2018-06-07Bibliographically approved
Lindh, E. M., Sandström, A. & Edman, L. (2014). Inkjet Printed Bilayer Light-Emitting Electrochemical Cells for Display and Lighting Applications. Small, 10(20), 4148-4153
Open this publication in new window or tab >>Inkjet Printed Bilayer Light-Emitting Electrochemical Cells for Display and Lighting Applications
2014 (English)In: Small, ISSN 1613-6810, E-ISSN 1613-6829, Vol. 10, no 20, p. 4148-4153Article in journal (Refereed) Published
Abstract [en]

A new bilayer light-emitting electrochemical cell (LEC) device, which allows well-defined patterned light emission through an easily adjustable, mask-free, and additive fabrication process, is reported. The bilayer stack comprises an inkjet-printed lattice of micrometer-sized electrolyte droplets, in a filled or patterned lattice configuration. On top of this, a thin layer of light-emitting compound is deposited from solution. The light emission is demonstrated to originate from regions proximate to the interfaces between the inkjetted electrolyte, the light-emitting compound, and one electrode, where bipolar electron/hole injection and electrochemical doping are facilitated by ion motion. By employing KCF3SO3 in poly(ethylene glycol) as the electrolyte, Super Yellow as the light-emitting compound, and two air-stabile electrodes, it is possible to realize filled lattice devices that feature uniform yellow-green light emission to the naked eye, and patterned lattice devices that deliver well-defined and high-contrast static messages with a pixel density of 170 PPI.

Place, publisher, year, edition, pages
John Wiley & Sons, 2014
Keywords
inkjet printing, light-emitting electrochemical cells, displays, patterning, conjugated polymers
National Category
Physical Sciences
Identifiers
urn:nbn:se:umu:diva-96951 (URN)10.1002/smll.201400840 (DOI)000344452500015 ()
Available from: 2015-02-25 Created: 2014-12-05 Last updated: 2019-02-05Bibliographically approved
Sandström, A., Asadpoordarvish, A., Enevold, J. & Edman, L. (2014). Spraying Light: Ambient-Air Fabrication of Large-Area Emissive Devices on Complex-Shaped Surfaces. Advanced Materials, 26(29), 4975-4980
Open this publication in new window or tab >>Spraying Light: Ambient-Air Fabrication of Large-Area Emissive Devices on Complex-Shaped Surfaces
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.

Keywords
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:nbn:se:umu:diva-93224 (URN)10.1002/adma.201401286 (DOI)000340500700011 ()
Available from: 2014-12-22 Created: 2014-09-15 Last updated: 2019-12-18Bibliographically approved
Sandström, A. (2013). Design and Fabrication of Light-Emitting Electrochemical Cells. (Doctoral dissertation). Umeå: Umeå universitet
Open this publication in new window or tab >>Design and Fabrication of Light-Emitting Electrochemical Cells
2013 (English)Doctoral thesis, comprehensive summary (Other academic)
Alternative title[sv]
Design och tillverkning av ljusemitterande elektrokemiska celler
Abstract [sv]

Glödlampan, en gång symbolen för mänsklig uppfinningsförmåga, är idag på väg att försvinna. Lysdioder och lågenergilampor har istället tagit över då dessa har betydligt längre livstid och högre effektivitet. Den tidigare så hyllade glödlampan anses numera vara en miljöbov, och förbud och restriktioner mot den blir allt vanligare. Trots detta så är de nya alternativen bara att betrakta som provisoriska steg på vägen mot en ideal ljuskälla, som idag tyvärr inte existerar. Lågenergilampor innehåller exempelvis kvicksilver, och utgör därmed ett direkt hot mot en användares hälsa. Både lysdioder och lågenergilampor består även av höga halter av andra tungmetaller, och är väldigt komplicerade att tillverka. Återvinning är därför ett måste, och en fullödig energibesparingsanalys måste ta hänsyn till den betydande energin som går åt vid tillverkningen. Till viss del kan detta lösas genom att göra komponenterna små och ljusstarka, men för att göra en sådan belysning angenäm används istället utrymmeskrävande och ofta energislukande lampskärmar. Lysdioder och lågenergilampor är helt enkelt bra, men långt ifrån perfekta.All elektronisk utrustning är idag beroende av metaller och inorganiska halvledare, vilket gör återvinning viktig och tillverkning komplicerad. Detta är kanske på väg att ändras då även organiska material, t.ex. plast, har visat sig kunna ha elektroniska egenskaper. Idag är organisk elektronik ett hett forskningsområde där material med liknande egenskaper som plast, fast med funktionella elektroniska egenskaper, undersöks och appliceras. Något som gör organiska material extra intressanta är att många kan lösas upp i vätskor, vilket möjliggör för skapandet av bläck. Detta leder i sin tur till möjligheter för användandet av storskaliga trycktekniker, t.ex. tidningspressar och bläckstråleskrivare, vilka leder till en stor kostnadsreduktion och förenklad tillverkning av lysande komponenter. Idag har plast redan ersatt många andra material i en mängd olika tillämpningar. Plastflaskor är vanligare än glasflaskor, och ylletröjor konkurerar idag med kläder gjorda av fleece och andra syntetiska fibrer. Med ljusemitterande plast finns det helt klart en möjlighet att en liknande utveckling kan ske även för lampor.Den här avhandlingen fokuserar på den fortsatta utvecklingen av den ljusemitterande elektrokemiska cellen (LEC), som 1995 uppfanns av Pei et al. LEC-tekniken använder sig av organiska halvledare för att konvertera elektrisk ström till ljus, men även en elektrolyt som möjliggör elektrokemisk dopning. Detta förbättrar den organiska halvledarens elektroniska egenskaper signifikant, vilket leder till mindre resistans och högre effektivitet hos den färdiga lysande komponenten.Visionen för denna och besläktade tekniker har sedan länge varit förverkligandet av en lysande tapet. Den här avhandlingen har försökt närma sig denna vision genom att visa hur en LEC kan uppnå hög effektivitet och lång livslängd, och samtidigt tillverkas i luft med storskaliga produktionsmetoder. Orsaker till en tidigare begränsad livslängd har identifierats och minimerats med hjälp av nya komponentstrukturer och materialformuleringar. En inkapslingsmetod presenteras också, vilken skyddar komponenten från syre och vatten som annars lätt reagerar med det dopade organiska materialet. Detta resulterar i en signifikant förbättring av livslängden.Genom att använda slot-die bestrykning och sprayning, båda kompatibla med rulle-till-rulle tillverkning, har möjligheter för storskalig produktion demonstrerats. Slutligen har en speciell metod för spraymålning av stora lysande ytor utvecklats.

Abstract [en]

The incandescent light bulb, once the very symbol for human ingenuity, is now being replaced by the next generation of lighting technologies such as the compact fluorescent lamp (CFL) and the light emitting diode (LED). The higher efficiencies and longer operational lifetimes of these new sources of illumination have led to the demise of the classic traditional bulb. However, it should be pointed out that the light sources that are taking over are better, but not perfect. The complex high-voltage electronic circuits and health hazardous materials required for their operation make them far from a sustainable eco-friendly option. Their fabrication is also complex, making the final product expensive. A new path forward might be through the use of plastics or other organic materials. Though not traditionally seen as electronically active, some organic materials do behave like inorganic semiconductors and substantial conductivity can be achieved by doping. Since plastics can be easily molded into complex shapes, or made into an ink using a solvent, it is expected that organic materials could revolutionize how we fabricate electronic devices in the future, and possibly replace inorganic crystals in the same way as plastics have replaced glass and wool for food storage and clothes. This thesis has focused on the light-emitting electrochemical cell (LEC), which was invented by Pei et al. in 1995. It employs organic semiconductors that can convert electricity to light, but also an electrolyte that further enhances the electronic properties of the semiconductor by allowing it to be electrochemically doped. This allows light-emitting films to be driven by a low-voltage source at a high efficiency. Unfortunately, the electrolyte has been shown to facilitate rapid degradation of the device under operation, which has historically severely limited the operational lifetime. Realizing the predicted high efficiency has also proven difficult. The purpose of this thesis is to bridge the gap between the LEC and the CFL. This is done by demonstrating efficient devices and improved operational lifetimes. Possible degradation mechanisms are identified and minimized using novel device architectures and optimized active layer compositions. An encapsulation method is presented, and shown to increase the LEC stability significantly by protecting it from ambient oxygen and water. The thesis further focuses on up-scaled fabrication under ambient air conditions, proving that light-emitting devices are compatible with solution-based and cost-efficient printing. This is achieved by a roll-to-roll compatible slot-die coating and a novel spray-depositing technique that alleviates problems stemming from dust particles and phase separation. A practical ambient air fabrication and a subsequent operation of light-emitting electrochemical cells with high efficiency are thus shown possible.

 

Place, publisher, year, edition, pages
Umeå: Umeå universitet, 2013. p. 61
Keywords
Light-emitting electrochemical cell, fabrication, organic semiconductors, organic electronics, ambient fabrication, roll-to-roll
National Category
Atom and Molecular Physics and Optics
Research subject
Physics
Identifiers
urn:nbn:se:umu:diva-79544 (URN)978-91-7459-691-5 (ISBN)
Public defence
2013-09-13, N300, Umeå universitet, Umeå, 09:47 (English)
Opponent
Supervisors
Available from: 2013-08-23 Created: 2013-08-22 Last updated: 2018-06-08Bibliographically approved
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