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Sökning: WAKA:ref > Inganäs Olle > Andersson M.R.

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1.
  • Aasmundtveit, K.E., et al. (författare)
  • Structural ordering in phenyl-substituted polythiophenes
  • 2000
  • Ingår i: Macromolecules. - 0024-9297. ; 33:15, s. 5481-5489
  • Tidskriftsartikel (refereegranskat)abstract
    • Various substituted poly(phenylthiophene)s have been studied by X-ray diffraction. They are semicrystalline, with very different degrees of crystallinity. Those with para-substituted phenyl groups have a low degree of crystallinity, whereas those with ortho-substituted phenyl groups are more crystalline. The most crystalline materials in this study have two equally long substituents on the phenyl ring, one at the ortho position and the other at the ortho or meta position on the opposite side of the phenyl ring. Poly(3-(2,5-dioctylphenyl)thiophene) (PDOPT) was most thoroughly studied, and a structural model is proposed. The structure of PDOPT is quite different from previously studied substituted polythiophenes in that the octyl side chains are directed normal to the thiophene planes. In this way, the conjugated polymer chains are kept separated from each other. Solution-cast and spin-cast PDOPT films are anisotropic, with the octyl side chains oriented normal to the film surface in both cases. This is contrary to the situation for poly(3-alkylthiophene)s, where solution-cast and spin-cast films orient in different ways.
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2.
  • Andersson, Mattias, et al. (författare)
  • Intrinsic and extrinsic influences on the temperature dependence of mobility in conjugated polymers
  • 2008
  • Ingår i: Organic electronics. - 1566-1199. ; 9:5, s. 569-574
  • Tidskriftsartikel (refereegranskat)abstract
    • The temperature dependence of charge carrier mobility in conjugated polymers and their blends with fullerenes is investigated with different electrical methods, through field effect transistor (FET), space charge limited current (SCLC) and charge extraction (CELIV) measurements. Simple models, such as the Gaussian disorder model (GDM), are shown to accurately predict the temperature behavior, and a good correlation between the different measurement methods is obtained. Inconsistent charge carrier concentrations in the modeling are explained through intrinsic non-equilibrium effects, and are responsible for the limited applicability of existing numerical models. A severe extrinsic influence from water in FETs with a hydrophilic insulator interface is also demonstrated. The presence of water leads to a significant overestimate of the disorder in the materials from measurements close to room temperature and erratic behavior in the 150-350 K range. To circumvent this problem it is shown to be necessary to measure under ultra high vacuum (UHV) conditions. © 2008 Elsevier B.V. All rights reserved.
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3.
  • Andersson, M.R., et al. (författare)
  • The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV
  • 2001
  • Ingår i: Synthetic metals. - 0379-6779. ; 119:1-3, s. 63-64
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the synthesis and characterisation of poly(2-(2',5'-bis(2?-ethylhexyloxy)phenyl)-1, 4-phenylenevinylene) (BEHP-PPV) polymerised under different conditions. The photoluminescence efficiencies (?PL) in the solid state of BEHP-PPV obtained at 144°C and 0°C are 28% and 60%, respectively. Polymerisation temperatures below 0°C decreases the molecular weight without changing the photoluminescence efficiency to any large extent.
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4.
  • Ding, L., et al. (författare)
  • Photovoltaic cells with a conjugated polyelectrolyte
  • 2000
  • Ingår i: Synthetic metals. - 0379-6779. ; 110:2, s. 133-140
  • Tidskriftsartikel (refereegranskat)abstract
    • We describe photovoltaic cells made from a novel conjugated polyelectrolyte, the lithium salt of poly(thiophene-3-acetic acid) (PTAA-Li). The aqueous solubility of this polyelectrolyte allows formation of blend electrodes with a dispersion of the metallic polymer Poly(Ethylene DiOxyThiophene) (PEDOT). The incident monochromatic photon to current conversion efficiency (IPCE) of the cells were improved up to 19% by blending PTAA-Li with PEDOT to modify the ITO electrode, in combination with the low bandgap polymer poly(3-(4-octylphenyl)thiophene) (POPT), and C60 as electron acceptor. We attribute the increase of efficiency to the improved contact area between the conjugated polyelectrolyte and PEDOT.
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5.
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6.
  • Gadisa, Abay, et al. (författare)
  • Red and near infrared polarized light emission from polyfluorene copolymer based light emitting diodes
  • 2007
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 90:11, s. 113510
  • Tidskriftsartikel (refereegranskat)abstract
    • The authors report polarized red, electroluminescence peak at 705  nm and near infrared, electroluminescence peak at 950  nm, light emission from light emitting diodes based on two polyfluorene copolymers. The copolymers are synthesized from a fluorene monomer combined with donor-acceptor-donor comonomers and designed to have a low band gap and form birefringent liquid crystalline phases. Emission occurs from aligned thin films of polymer layers. The emissive layers are aligned by spin coating on a layer of rubbed conducting polymer poly(3,4-ethylene dioxythiophene)-poly(styrene sulphonate) and thermally converted into glassy nematic liquid crystalline state.
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7.
  • Inganäs, Olle, et al. (författare)
  • Low bandgap alternating polyfluorene copolymers in plastic photodiodes and solar cells
  • 2004
  • Ingår i: Applied Physics A : Materials Science & Processing. - 0947-8396. ; 79:1, s. 31-35
  • Tidskriftsartikel (refereegranskat)abstract
    • We report a comparative study of plastic photodiodes using four different copolymers of fluorene, with a variation of alkyl side chain length and chemical structure. Photodiode materials are formed by blending the polymers with a fullerene derivative and spincoating the blend solution. A photovoltage of 1 V is obtained in devices, where the anode is a doped polymer and the cathode is LiF/Al. Monochromatic quantum efficiencies are better than 40% over most of the absorption range, and under solar light AM 1.5 simulation, we reach energy efficiencies beyond 2%. The high fill factors obtained in some of the devices indicate that these are of interest for more elaborate optimisation. Reasons for the benign electrical transport are discussed. © Springer-Verlag 2004.
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8.
  • Inganäs, Olle, et al. (författare)
  • Recent progress in thin film organic photodiodes
  • 2001
  • Ingår i: Synthetic metals. - 0379-6779. ; 121:1-3, s. 1525-1528
  • Tidskriftsartikel (refereegranskat)abstract
    • We review current developments in organic photodiodes, with special reference to multilayer thin film optics, and modeling of organic donor-acceptor photodiodes. We indicate possibilities to enhance light absorption in devices by nanopatterning as well as by blending, and also discuss materials science issues of nanostructure in blends and in vertically stratified multilayer devices. Our current best devices have external efficiencies of 30-50% in between 400-600 nm, and show fill factors of 0.54 illuminated under weak monochromatic light.
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9.
  • Johansson, D.M., et al. (författare)
  • Convenient synthetic route to poly(p-phenylene-1,2-diphenylvinylenes)
  • 2000
  • Ingår i: Synthetic metals. - 0379-6779. ; 113:3, s. 293-297
  • Tidskriftsartikel (refereegranskat)abstract
    • The synthesis and characterization of two soluble poly(p-phenylenevinylene)s substituted with phenyl groups on the vinylene moiety is reported. The polymers are poly(1,4-phenylene-1,2-diphenylvinylene) (PPV-DP) and poly(1,4-phenylene-1,2-(3'-(2?-ethylhexyloxy))-diphenylvinylene) (PPV-mEHDP). The monomers containing chloromethyl groups were polymerized with excess potassium tert-butoxide in dioxane at room temperature. The polymerization conditions are optimized. The photoluminescence (PL) properties of the polymers showed an increase in the PL efficiency in film from 19% for PPV-DP to 37% for PPV-mEHDP. Both polymers emitted green light with higher intensity in film than in solution.
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10.
  • Johansson, D.M., et al. (författare)
  • Synthesis and characterisation of polyfluorenes with light-emitting segments
  • 2001
  • Ingår i: Synthetic metals. - 0379-6779. ; 121:1-3, s. 1761-1762
  • Tidskriftsartikel (refereegranskat)abstract
    • We present the synthesis and characterisation of two copolymers. They consists of poly(9-hexyl-9-(2'-ethylhexyl)fluorene) (HEH-PF) with a small amount of another polymer with a narrow band-gap. The synthetic route was designed to allow the incorporation of only one low band-gap segment per polymer chain. Photoluminescence measurements showed that energy transfer from the PF-segments to the low band-gap segments, did occur. In the solid state, all emissions were detected from the low band-gap segments with photoluminescence quantum yields up to 68%. One copolymer showed a low threshold for lasing (2 µJ/cm2) in a microcavity device.
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  • Resultat 1-10 av 31
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