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Physics of materials in organic electronics
Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
2004 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The research included in this thesis is regarding materials physics in organic electronics. The thesis consists of two projects: one applied and one basic science in nature. The applied project concerns modification of charge injection properties in organic electronics. The choice of the materials used as anodes and cathodes in polymer light emitting devices, PLEDs, plays a crucial role in device performance. The electrodes, often multi-component/layer systems, need to be chosen in such a way that that they fit the properties of the active material. Here, the electronic, chemical and physical properties of materials for so-called hole transporting layers (HTL) were studied and used to explain and improve the performance of polymer-based light emitting diodes (PLED). The study focused on the properties most important for devices, e.g. film morphology, work function and chemical composition, and the results were compared to PLED 1-V characteristics and luminescence efficiency. The second project aimed to provide basic understanding of issues concerning charge confinement (and charge injection) in small molecules. The n-doping of an component of an organic-based magnetic semiconductor was studied as a first step towards understanding the electronic and magnetic properties of the actual magnetic material.

Place, publisher, year, edition, pages
Norrköping, Sweden: Linköpings universitet , 2004. , 43 p.
Series
Linköping Studies in Science and Technology. Thesis, ISSN 0280-7971 ; 1086
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-22732ISRN: LiU-TEK-LIC-2004:15Local ID: 2037ISBN: 91-7373-932-4 (print)OAI: oai:DiVA.org:liu-22732DiVA: diva2:243045
Available from: 2009-10-07 Created: 2009-10-07 Last updated: 2013-10-31
List of papers
1. Study and comparison of conducting polymer hole injection layers in light emitting devices
Open this publication in new window or tab >>Study and comparison of conducting polymer hole injection layers in light emitting devices
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2005 (English)In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 6, no 1, 21-33 p.Article in journal (Refereed) Published
Abstract [en]

A set of polyaniline- and poly(3,4-ethylene dioxythiophene)-based materials were studied as hole injection layers in polymer light emitting devices. The choice of polymeric counterion/dopant poly(styrenesulfonic acid), and poly(acrylamido-2-methyl-1-propanesulfonic acid), and poly(acrylamide) blended with polyaniline/poly(acrylamido-2-methyl-1-propanesulfonic acid) was found to influence both work function and film morphology, which in turn affects device performance. The work functions of the polymer films spanned the range of over 1 eV and the surface region of the films were found to be low in conducting polymer content compared to the bulk. This was particularly the case of the polyaniline/poly(acrylamido-2-methyl-1-propanesulfonic acid) blended with poly(acrylamide) which showed device efficiency equal to that of the poly(3,4-ethylene dioxythiophene)–poly(styrenesulfonic acid) reference. The turn on voltage, however, was significantly larger, likely due to the insulating poly(acrylamide)-rich surface region of the polyaniline/poly(acrylamido-2-methyl-1-propanesulfonic acid)/poly(acrylamide) film. The polymer blend of polyaniline/poly(styrenesulfonic acid) yielded the highest work function (5.5 ± 0.1 eV).

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-32255 (URN)10.1016/j.orgel.2005.02.001 (DOI)18135 (Local ID)18135 (Archive number)18135 (OAI)
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2017-12-13
2. Poly(3.4-ethylene dioxythiophene)- and polyaniliane-Poly(perfluoroethylenesulfonic acid) as hole injecting layers in polymer light emitting devices
Open this publication in new window or tab >>Poly(3.4-ethylene dioxythiophene)- and polyaniliane-Poly(perfluoroethylenesulfonic acid) as hole injecting layers in polymer light emitting devices
(English)Manuscript (preprint) (Other academic)
Abstract [en]

We present a study of poly(3,4-ethylene dioxythiophene), PEDOT, and polyaniline, where poly(perfluoroethylenesulfonic acid), PFESA has been used as counter ion and dopant respectively. The study was done in order to establish how the material petfonns as hole injecting layers in polymer light emitting devices. A total of 19 different PEDOT-PFESA samples and three different PAni-PFESA systems were studied, each with a different acidity, ranging between pH 1.6 to pH 7.7. The highest work function obtained was 6.0 eV and work function and acidity correlate such that significantly higher work functions are obtained for higher acidities. Photoelectron spectroscopy and Atomic Force Microscopy data suggest that the resulting fihns have grain structured morphology where the PAni-PFESA and PEDOT-PFESA systems form inverse micelles, i.e. PEDOT or PAni together with counter ions as an inner core surrounded by mainly the PFESA backbone.

National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-85555 (URN)
Available from: 2012-11-23 Created: 2012-11-23 Last updated: 2013-10-31
3. Coulomb interactions in rubidium-doped tetracyanoethylene: a model system for organometallic magnets
Open this publication in new window or tab >>Coulomb interactions in rubidium-doped tetracyanoethylene: a model system for organometallic magnets
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2004 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 69, no 16, 165208- p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of tetracyanoethylene (TCNE) has been studied both in its pristine state and upon stepwise rubidium intercalation, by UV and x-ray photoelectron spectroscopy as well as with theoretical calculations. The intercalated system may serve as a model for TCNE-based organometallic magnets, of which the electronic structure remains largely unknown. Rubidium is found to n-dope the TCNE molecules forming Rb+TCNE- with almost complete charge transfer. Calculations show a spin splitting of the former highest occupied molecular orbital level upon Rb doping. We see no evidence for the formation of doubly charged TCNE molecules. A gap opens up at the Fermi energy for Rb+TCNE- due to on-site Coulomb interactions. We estimate the on-site Coulomb interaction of amorphous TCNE doped with Rb to be ∼2 eV.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-13871 (URN)10.1103/PhysRevB.69.165208 (DOI)
Available from: 2006-06-28 Created: 2006-06-28 Last updated: 2017-12-13

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