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  • 1.
    Anselmo, Ana Sofia
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Dzwilewski, Andrzej
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Rysz, Jakub
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Budkowski, Andrzej
    M. Smoluchowski Insitute of Physics, Jagiellonian University, Reymonta 4, Krakow 30–059, Poland.
    Svensson, Krister
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    van Stam, Jan
    Karlstad University, Faculty of Technology and Science, Department of Chemistry and Biomedical Sciences.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Polymer solar cells: Visualizing vertical phase separation in solution-processed films of polymer fullerene blends2012In: Proceedings of the 5th International Symposium Technologies for Polymer Electronics - TPE 12 / [ed] Hans-Klaus Roth, Klaus Heinemann, Ilmenau, Germany: Universitätsverlag Ilmenau , 2012, p. 125-128Conference paper (Refereed)
  • 2.
    Ekhagen, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Stability of electron acceptor materials for organic solar cells: a work function study of C60/C70 derivatives and N22002019Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Thin films of the fullerenes PC60BM and PC70BM and the non-fullerene N2200, three popular electron acceptor materials in organic photovoltaics, have been studied, using both the Kelvin probe method as well as ultraviolet photoelectron spectroscopy. With these methods the work function was measured, as well as the highest occupied molecular orbital (HOMO) onset. Additionally band bending effects were studied by illuminating the samples while measuring the work function with the Kelvin probe so called surface photovoltage. Sample of each material was exposed to either air and simulated sunlight or N2 and simulated sunlight, for different length of time, to observe how the materials work function evolves after exposure to the different conditions. It was observed that, as expected from previous studies, that PC60BM was less photo-stable than PC70BM. Additionally, the work function of PC60BM changed significantly by storage in N2. Each material after exposure for 24h to air and light, was annealed and measured with the Kelvin probe. A restoring effect was observed,  for the non-fullerene material N2200. All three materials developed an increasing surface photovoltage, which suggest increased band bending, when exposed to air and light, indicating that due phot-oxidization, charges are redistributed at the surface of the film. The fullerenes showed a larger surface photovoltage effect than the non-fullerene materials. A difference between the work function values obtained from the Kelvin probe method and the ultraviolet photoelectron spectroscopy could be seen, however the exact reason for this couldn't be isolated within this thesis, but was discussed.

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    Ekhagen_Thesis
  • 3.
    Müller, Christian
    et al.
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Bergqvist, Jonas
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Vandewal, Koen
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Tvingstedt, Kristoffer
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Anselmo, Ana Sofia
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Magnusson, Roger
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Alonso, M. Isabel
    Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, ES-08193 Bellaterra, Spain.
    Moons, Ellen
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering. Karlstad University, Faculty of Technology and Science, Materials Science.
    Arwin, Hans
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Campoy-Quiles, Mariano
    Institut de Ciencia de Materials de Barcelona (ICMAB-CSIC), Esfera UAB, ES-08193 Bellaterra, Spain.
    Inganäs, Olle
    Department of Physics, Chemistry and Biology, Linköpings universitet, Sweden.
    Phase behaviour of liquid-crystalline polymer/fullerene organic photovoltaic blends: thermal stability and miscibility2011In: Journal of Materials Chemistry, ISSN 0959-9428, E-ISSN 1364-5501, Vol. 21, p. 10676-10684Article in journal (Refereed)
    Abstract [en]

    The thermal behaviour of an organic photovoltaic (OPV) binary system comprised of a liquidcrystalline fluorene-based polymer and a fullerene derivative is investigated. We employ variabletemperature ellipsometry complemented by photo- and electroluminescence spectroscopy as well as optical microscopy and scanning force nanoscopy to explore phase transitions of blend thin films. The high glass transition temperature correlates with the good thermal stability of solar cells based on these materials. Furthermore, we observe partial miscibility of the donor and acceptor together with the tendency of excess fullerene derivative to segregate into exceedingly large domains. Thus, for charge generation less adequate bulk-heterojunction nanostructures are poised to develop if this mixture is exposed to more elevated temperatures. Gratifyingly, the solubility of the fullerene derivative in the polymer phase is found to decrease if a higher molecular-weight polymer fraction is employed, which offers routes towards improving the photovoltaic performance of non-crystalline OPV blends.

  • 4.
    Nilsson, Rickard
    Karlstad University, Faculty of Health, Science and Technology (starting 2013).
    Optimization of pneumatic activity sensor: Development of a low friction seal2019Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis, the development of a new type of seal is presented along with the steps taken to attain the conclusive design. The results are presented in this paper as a cross-sectioned CAD-model along with the selection of materials and suggestions for future work. The project was commissioned by the multi-discipline engineering consultancy company Projektengagemang AB in Karlstad, Sweden, and carried out as a master’s thesis at Karlstad University. The commission was due to a demand for a new type of sealing solution, as friction is a problem within the field of micro-pneumatics. The work done consists of a study of different low-friction materials where a 30/70 PTFE/PEEK compound was selected as it displayed promising friction and wear properties. The material was then implemented into a design concluded by employing a product development process. The result rendered a prototype for a new kind of low-friction seal which uses the fluid pressure to achieve a sealing contact load between a piston/rod and the seal, which also was the goal set to achieve at the start of the project. Additionally, a design of experiments study was conducted to settle what design parameters were significant with respect to the contact load. For proceeding, making the concept a product ready for production, additional work is needed in the form of experimental material testing, development of a leakage model to optimize the contact load, determination of temperature and creep behaviour, as well as sufficient field testing. Lastly, a die tool must be designed for manufacturing with injection moulding as well as determining if any further processing is required.

    Download full text (pdf)
    Arkivfil
  • 5.
    Nyflött, Åsa
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Chemical Sciences (from 2013).
    Structure-Performance Relations of Oxygen Barriers for Food Packaging2017Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Food packaging should ensure the safety and quality of food, minimize spoilage and provide an easy way of storing and handling it. Barrier coatings are generally used to meet the demands placed on fibre-based food packages, as these have the ability to regulate the amount of gases that can enter them. Some gases are detrimental to food quality: oxygen, for example, initiates lipid oxidation in fatty foods. Using both experimental data and computer modelling, this thesis explains some aspects of how the structure of barrier coatings influences the mass transport of oxygen with the aim of obtaining essential knowledge that can be used to optimize the performance of barriers.

    Barrier coatings are produced from polyvinyl alcohol and kaolin blends that are coated onto a polymeric support. The chemical and physical structures of these barriers were characterized according to their influence on permeability in various climates. At a low concentration of kaolin, the crystallinity of polyvinyl alcohol decreased; in the thinner films, the kaolin particles were orientated in the basal plane of the barrier coating. The experimental results indicated a complex interplay between the polymer and the filler with respect to permeability.

    A computer model for permeability incorporating theories for the filled polymeric layer to include the polymer crystallinity, addition of filler, filler aspect ratio and surrounding moisture was developed. The model shows that mass transport was affected by the aspect ratio of the clay in combination with the clay concentration, as well as the polymer crystallinity. The combined model agreed with the experiments, showing that it is possible to combine different theories into one model that can be used to predict the mass transport.

    Four barrier coatings: polyethylene, ethylene vinyl alcohol + kaolin, latex + kaolin and starch were evaluated using the parameters of greenhouse gas emissions and product costs. After the production of the barrier material, the coating process and the end-of-life handling scenarios were analysed, it emerged that starch had the lowest environmental impact and latex + kaolin had the highest.

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  • 6.
    Pavlopoulou, E.
    et al.
    University Bordeaux, France.
    Fleury, G.
    University Bordeaux, France.
    Deribew, Dargie
    University Bordeaux, France.
    Cousin, F.
    CEA Saclay, France.
    Geoghegan, M.
    University Sheffield, England.
    Hadziioannou, G.
    University Bordeaux, France.
    Phase separation-driven stratification in conventional and inverted P3HT:PCBM organic solar cells2013In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 14, no 5, p. 1249-1254Article in journal (Refereed)
    Abstract [en]

    We have used neutron reflectivity to investigate the stratification of poly(3-hexylthiophene) (P3HT) and phenyl-C-61-butyric acid methyl ester (PCBM) blend films. Films were spun-cast on poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS) and titanium oxide (TiOx) layers to mimic the procedures followed for the fabrication of conventional and inverted organic photovoltaics respectively. The resultant scattering length density profiles reveal a PCBM-rich layer is formed in the vicinity of PEDOT: PSS or TiOx, while PCBM is depleted at the free surface of the film. PCBM segregation close to the substrate is further enhanced by annealing. This stratification is considered to be favorable only for inverted devices. (C) 2013 Elsevier B. V. All rights reserved.

  • 7.
    Renaud, Cedric
    et al.
    University Bordeaux, France.
    Mougnier, Sebastien-Jun
    University Bordeaux, France.
    Pavlopoulou, Eleni
    University Bordeaux, France.
    Brochon, Cyril
    University Bordeaux, France.
    Fleury, Guillaume
    University Bordeaux, France.
    Deribew, Dargie
    University Bordeaux, France.
    Portale, Giuseppe
    University Bordeaux, France.
    Cloutet, Eric
    University Bordeaux, France.
    Chambon, Sylvain
    University Bordeaux, France.
    Vignau, Laurence
    University Bordeaux, France.
    Hadziioannou, Georges
    University Bordeaux, France.
    Block Copolymer as a Nanostructuring Agent for High-Efficiency and Annealing-Free Bulk Heterojunction Organic Solar Cells2012In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 24, no 16, p. 2196-2201Article in journal (Refereed)
1 - 7 of 7
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