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  • 1.
    Aasmundtveit, K.E.
    et al.
    Institutt for Fysikk, Norges Tekn.-Naturvitenskapelige U., Trondheim, Norway.
    Samuelsen, E.J.
    Institutt for Fysikk, Norges Tekn.-Naturvitenskapelige U., Trondheim, Norway.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Pettersson, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Johansson, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Ferrer, S.
    Europ. Synchrt. Radiat. Facil. (E., F-38043, Grenoble, France.
    Structural aspects of electrochemical doping and dedoping of poly(3,4-ethylenedioxythiophene)2000In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 113, no 1, p. 93-97Article in journal (Refereed)
    Abstract [en]

    Electrochemical dedoping and redoping of p-toluene sulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT) has been studied with in situ grazing incidence diffraction with water used as an electrolyte. The diffraction peak positions and integrated intensities do not change significantly during doping and dedoping, while the peak widths increase upon dedoping and decrease upon doping. This implies that the lattice parameters and the relative positions of the polymer chains and the p-toluene sulfonate ions remain unchanged, the redox processes being carried out by the motion of smaller ions between the polymer and the electrolyte, and that the structural order decreases upon dedoping and increases upon doping in a reversible manner.

  • 2.
    Admassie, Shimelis
    et al.
    Addis Ababa University.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Mammo, Wendimagegn
    Chalmers university of Technology.
    Perzon, Erik
    Chalmers university of Technology.
    Andersson, Mats R
    Chalmers university of Technology.
    Electrochemical and optical studies of the band gaps of alternating polyfluorene copolymers2006In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 156, no 7-8, p. 614-623Article in journal (Refereed)
    Abstract [en]

    The electrochemical and optical properties of a series of alternating polyfluorene copolymers with low band gaps were determined. These polymers incorporated fluorene units alternating with groups including electron-withdrawing (A) and electron-donating (D) groups in donor-acceptor-donor (DAD) sequence to achieve the lowering of band gaps. The polymers were solvent-casted on platinum disk electrode and the band gaps were estimated from cyclic voltammetry (CV). These values were compared with values obtained from optical absorption measurements. Although the electrochemically determined band gaps were found to be slightly higher than the optical band gap in most cases, values are well correlated. The values of the band gaps determined range from 2.1 to 1.3 eV. © 2006 Elsevier B.V. All rights reserved.

  • 3.
    Ail, Ujwala
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Ullah Khan, Zia
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Granberg, Hjalmar
    Innventia AB, Sweden.
    Berthold, Fredrik
    Innventia AB, Sweden.
    Parasuraman, Rajasekar
    Mat Research Centre, India.
    Urnarji, Arun M.
    Mat Research Centre, India.
    Slettengren, Kerstin
    Innventia AB, Sweden.
    Pettersson, Henrik
    Innventia AB, Sweden.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Room temperature synthesis of transition metal silicide-conducting polymer micro-composites for thermoelectric applications2017In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 225, p. 55-63Article in journal (Refereed)
    Abstract [en]

    Organic polymer thermoelectrics (TE) as well as transition metal (TM) silicides are two thermoelectric class of materials of interest because they are composed of atomic elements of high abundatice; which is a prerequisite for mass implementation of thermoelectric (TE) solutions for solar and waste heat recovery. But both materials have drawbacks when it comes to finding low-cost manufacturing. The metal silicide needs high temperature (amp;gt;1000 degrees C) for creating TE legs in a device from solid powder, but it is easy to achieve long TE legs in this case. On the contrary, organic TEs are synthesized at low temperature from solution. However, it is difficult to form long legs or thick films because of their low solubility. In this work, we propose a novel method for the room temperature synthesis of TE composite containing the microparticles of chromium disilicide; CrSi2 (inorganic filler) in an organic matrix of nanofibrillated cellulose-poly(3,4-ethyelenedioxythiophene)-polystyrene sulfonate (NFC-PEDOT:PSS). With this method, it is easy to create long TE legs in a room temperature process. The originality of the approach is the use of conducting polymer aerogel microparticles mixed with CrSi2 microparticles to obtain a composite solid at room temperature under pressure. We foresee that the method can be scaled up to fabricate and pattern TE modules. The composite has an electrical conductivity (sigma) of 5.4 +/- 0.5 S/cm and the Seebeck coefficient (a) of 88 +/- 9 mu V/K, power factor (alpha(2)sigma) of 4 +/- 1 mu Wm(-1) K-2 at room temperature. At a temperature difference of 32 degrees C, the output power/unit area drawn across the load, with the resistance same as the internal resistance of the device is 0.6 +/- 0.1 mu W/cm(2). (C) 2017 Elsevier B.V. All rights reserved.

  • 4.
    Andersson, Mats R.
    et al.
    Chalmers Tekniska Högskola.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Gustafsson, Göran
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hjertberg, T.
    Chalmers Tekniska Högskola.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Wennerström, O.
    Chalmers Tekniska Högskola.
    Synthesis of poly(alkylthiophenes) for light-emitting diodes1995In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 71, no 1-3, p. 2183-2184Article in journal (Refereed)
    Abstract [en]

    We have demonstrated a general way to tune the emission of poly(alkylthiophenes) by using steric interaction between the repeating units. Light-emitting diodes prepared of the polymers have blue to near-infrared emission.

  • 5.
    Andersson, Mats R.
    et al.
    Chalmers Tekniska Högskola.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Olinga, T.
    Chalmers Tekniska Högskola.
    Hjertberg, T.
    Chalmers Tekniska Högskola.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Wennerström, O.
    Chalmers Tekniska Högskola.
    Improved photoluminescence efficiency of films from conjugated polymers1997In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 85, no 1-3, p. 1383-1384Article in journal (Refereed)
    Abstract [en]

    We have demonstrated two general ways to increase the photoluminescence efficiency of films from conjugated polymers. One is to disperse the conjugated polymer on a molecular level by using attractive forces between the conjugated polymer and the matrix. The other method is to substitute the conjugated polymer with side chains which separates the conjugated backbones. Using this idea a new poly(thiophene) with a photoluminescence efficiency of 16% in films has been prepared. LEDs from this polymer exhibit an external efficiency of 0.1% for single layer and 0.7% for double layer diodes.

  • 6.
    Andersson, M.R.
    et al.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Johansson, D.M.
    Department of Organic Chemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Theander, M.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 119, no 1-3, p. 63-64Article in journal (Refereed)
    Abstract [en]

    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.

  • 7.
    Andersson, Peter
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Robinson, Nathaniel D.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Diodes Based on Blends of Molecular Switches and Conjugated Polymers2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, ISSN 0379-6779, Vol. 150, no 3, p. 217-221Article in journal (Refereed)
    Abstract [en]

    Here we report polymer diodes based on a conjugated polymer host and a dispersed molecular switch. In this case, the molecular switch is a photochromic (PC) molecule that can be reversibly switched between low and high energy gap states, triggered by exposure to ultra-violet and visible light, respectively. While dispersed inside the conjugated polymer bulk and switched to its low energy gap state, the PC molecules act as traps for holes. Solid-state blends of this PC material and conjugated polymers have been demonstrated in diodes. The state of the PC molecule controls the current density versus voltage (JV) characteristics of the resulting diode. Both poly(2-methoxy-5(2′-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV) and poly(3-hexylthiophene-2,5-diyl) (P3HT) host materials have been studied. The two conjugated polymers resulted in differing JV switching characteristics. A more pronounced JV switch is observed with MEH-PPV than with P3HT. We postulate that the PC material, while switched to its low energy gap state, act as traps in both the conjugated polymers but at different trap depth energies.

  • 8.
    Bantikassegn, W.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Dannetun, Per
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Proceedings of the International Conference on Science and Technology of Synthetic Metals Electronic properties of polypyrrole (polystyrene-sulphonate)/metal junctions1993In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 55, no 1, p. 36-42Article in journal (Refereed)
    Abstract [en]

    The nature of polymer/metal interfaces is decisive for the operation of polymer based electronic devices. At such interfaces charge transport may be affected by barrier formation, or by formation of insulating interfaces of various types. We have prepared thin films of conducting polypyrrole doped with large polymeric anions of polystyrenesulphonate for studies in metal/polymer junctions. Aluminium and gold contacts are vacuum deposited to form metal/polymer/gold sandwich structures. The current-voltage characteristics show that the interface between polypyrrole and gold is ohmic with no current limitation. However, the aluminium/polypyrrole interface forms highly resistive and nonohmic contacts. Photoelectron spectroscopy using UV and X-ray photons reveals a decrease of the work function upon Al deposition, reactions between Al and the sulphonate anions, and immediate oxidation of the aluminium upon exposure to oxygen. These observations corroborate the interpretation that the current limitation found at Al/polypyrrole junctions is due to formation of insulating aluminium oxide, not excluding reactions between the metal and dopant. It is also pointed out that interfaces between reactive metals and polymers are prone to such oxide interface formation, considering the high diffusivity of oxygen in many polymers.

  • 9.
    Berggren, Magnus
    et al.
    Bell Laboratories, Murray Hill, USA.
    Dodabalapur, A
    Bell Laboratories, Murray Hill, USA.
    Slusher, RE
    Bell Laboratories, Murray Hill, USA.
    Bao, Z
    Bell Laboratories, Murray Hill, USA.
    Organic lasers based on Forster transfer1997In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 91, no 1-3, p. 65-68Article in journal (Refereed)
    Abstract [en]

    The light amplification characteristics of organic guest-host systems with Forster transfer from absorbing small molecule hosts to dye/ polymer dopants are described. Such material systems are shown to be very promising for use in low-threshold organic lasers. A number of laser resonators have been experimentally realized with Forster gain media including microdisk, ring, spheroid, and distributed Bragg reflector lasers. (C) 1997 Elsevier Science S.A.

  • 10.
    Berggren, Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology. null.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology. null.
    Granlund, Thomas
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. null.
    Guo, S,
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology. null.
    Gustafsson, Göran
    IMC, Linköping.
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Polymer light-emitting diodes placed in microcavities1996In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 76, no 1-3, p. 121-123Article in journal (Refereed)
    Abstract [en]

    The use of resonant optical microcavities to influence the emission properties of conjugated polymer light-emitting diodes (LEDs) is reported. The microcavities, which are built using metallic mirrors and polymeric spacers, incorporate polymer LEDs in between the mirrors. We report experimental results of polymer LEDs based on substituted polythiophenes. The effects include substantial narrowing of the spectral width of the emitted light, enhancement of the emission at the microcavity resonance, and coupling of two emission processes to different resonance modes in the same cavity.

  • 11.
    Berggren, Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Gustafsson, Göran
    Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Hjertberg, Thomas
    Chalmers Tekniska Högskola.
    Wennerström, Olof
    Chalmers Tekniska Högskola.
    Controlling colour by voltage in polymer light emitting diodes1995In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 71, no 1-3, p. 2185-2186Article in journal (Refereed)
    Abstract [en]

    We report electroluminescence using different substituted polythiophenes as the emitting mterial. Different substituents cause different sterical interacion which force the thiophene rings out of planarity. This results in different bandgaps. Colours from blue to near infrared have been demonstrated in electroluminescent devices. We also demonstrate voltage controlled electroluminescence using mixtures of these polymers.

  • 12. Birgerson, J.
    et al.
    Janssen, F.J.J.
    Department of Applied Physics, Dutch Polymer Institute, Eindhoven University of Technology, P.O. Box 513, 5600 MB Eindhoven, Netherlands.
    Denier, van der Gon A.W.
    Tsukahara, Y.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Kaeriyama, K.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Doped polymeric cathodes for PPV/Al based LEDs2002In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 132, no 1, p. 57-61Article in journal (Refereed)
    Abstract [en]

    The effect of Li-doping in poly(para-phenylenevinylene) (PPV) based light emitting devices has been studied. In a standard structure with an indium tin oxide (ITO) anode, poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS)-layer and an active PPV-layer, the effects of a thin (around 1 Å) Li-layer and a thin layer, (50 Å), of a large bandgap polymer, poly(2,5-diheptyl-1,4-phenylene-alt-1,4-naphthylene) (P14NHP) between the PPV and the aluminum cathode have been studied in terms of IV-characteristics and efficiency. The Li-atoms dope the interfacial layer of the PPV as seen by photoelectron spectroscopy. A thin layer of Li improves the charge balance by decreasing the energy barrier for injection of electrons for the Al/Li/PPV/PEDOT-PSS/ITO device. The efficient electron injection originates from a Fermi level alignment between the doped polymer and the aluminum cathode, which reduces the energy barrier. A thin layer of the large bandgap polymer P14NHP, between the PPV and Al contact, increases the light output and efficiency by blocking the holes. In addition, it may also reduce the light quenching by moving the region of recombination away from the Al-contact. The addition of a Li-layer on top of P14NHP leads to an increase of the quantum efficiency, because of better electron injection. © 2002 Elsevier Science B.V. All rights reserved.

  • 13. Birgerson, J.
    et al.
    Johansson, N.
    Pohl, A.
    Logdlund, M.
    Lögdlund, M., ACREO AB, Bredgatan 34, S-602 21 Norrköping, Sweden.
    Tsukahara, Y.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Kaeriyama, K.
    Dept. of Chem. and Mat. Technology, Kyoto Institute of Technology, Kyoto 606-8585, Japan.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electronic structure of some conjugated polymers for electron transport2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 122, no 1, p. 67-72Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic structure of three different, strictly alternating copolymers, poly(2,5-diheptyl-1,4-phenylene-alt-1,4-naphthylene) (P14NHP), poly(2,5-diheptyl-1,4-phenylene-alt-2,6-naphthylene) (P26NHP) and poly(2,5-diheptyl-1,4-phenylene-alt-9,10-anthrylene) (P910AHP), have been studied by photoelectron spectroscopy and optical absorption spectroscopy. The experimental results have been analyzed using the results of quantum chemical calculations. In the geometrical structure of all three of the polymers there are large torsion angles between the phenylene unit and the naphthylene or anthrylene units. These large torsion angles lead to localization of the p-electron wave functions, and minimal conjugation along the polymer backbone. For all three polymers, the highest occupied molecular orbital is completely localized to the naphthylene or anthrylene unit. The frontier molecular orbital wave functions are very reminiscent of the highest occupied orbitals of the isolated naphthalene or anthracene molecules. The optical absorption spectra of all three polymers verify the existence of large optical band gaps, consistent with the large torsion angels. The first several optical transitions in the polymers are also very reminiscent of the transitions in single naphthalene and anthracene molecules.

  • 14.
    Bolognesi, A.
    et al.
    Ist. lo Stud. delle Macromolecole, CNR, Via E. Bassini 15, 20133 Milano, Italy.
    Giacometti, Schieroni A.
    Giacometti Schieroni, A., Ist. lo Stud. delle Macromolecole, CNR, Via E. Bassini 15, 20133 Milano, Italy.
    Botta, C.
    Ist. lo Stud. delle Macromolecole, CNR, Via E. Bassini 15, 20133 Milano, Italy.
    Marinelli, M.
    Ist. lo Stud. delle Macromolecole, CNR, Via E. Bassini 15, 20133 Milano, Italy.
    Mendichi, R.
    Ist. lo Stud. delle Macromolecole, CNR, Via E. Bassini 15, 20133 Milano, Italy.
    Rolandi, R.
    Ist. Naz. per la Fis. della Materiae, Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
    Relini, A.
    Ist. Naz. per la Fis. della Materiae, Dipartimento di Fisica, Università di Genova, Via Dodecaneso 33, 16146 Genova, Italy.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Theandher, M.
    High photoluminescence efficiency in substituted polythiophene aggregates2003In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 139, no 2, p. 303-310Article in journal (Refereed)
    Abstract [en]

    In this paper we discuss the optical (absorption and photoluminescence) and solvatochromic properties of a newly synthesized alternating copolymer based on poly(3-alkylthiophene) structure. In this copolymer an unsubstituted thiophene ring is linked to a 3-alkyl-substituted thiophene, the two repeating units being alternated in the copolymer chains. Moreover, a bulky group, THP, with high steric hindrance has been introduced in the side chain. This copolymer, designed to preserve the backbone planarity of polythiophenes and to prevent a close packing arrangement through the non-regioregular insertion of the bulky substituted monomer, shows high PL quantum yield in the solid state and in solution aggregates. The electroluminescence of this copolymer is reported for a simple single layer device. © 2003 Elsevier Science B.V. All rights reserved.

  • 15.
    Bröms, P.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Xing, K. Z.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Dannetun, Per
    Groupe de Physique des Solides, Tour 23-2, place Jussieu, F-752 51 Paris Cedex 05, France.
    Cornil, J.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Santos, D.A. dos
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Brédas, J. L.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Moratti, S. C.
    University Chemical Laboratory, University of Cambridge, Cambridge CB2 1EW, UK.
    Holmes, A. B.
    University Chemical Laboratory, University of Cambridge, Cambridge CB2 1EW, UK.
    Friend, R. H.
    Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK.
    Optical absorption studies of sodium doped poly(cyanoterephthalylidene)1994In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 67, no 1-3, p. 93-96Article in journal (Refereed)
    Abstract [en]

    The effects of doping poly(cyanoterephthalylidene) with sodium in ultrahighvacuum been studied by optical absorption spectroscopy. Upon doping, new optical transitions are observed within the bandgap; the characteristics of these transitions are consistent with the formation of bipolarons. The optical absorption results are confirmed by direct measurements of the doping-induced gap states using ultraviolet photoelectron spectroscopy.

  • 16.
    Carlegrim, Elin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Zhan, Yiqiang
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    de Jong, M. P.
    MESA Institute for Nanotechnology, University of Twente, 7500 AE Enschede, The Netherlands.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Electronic structure of thin film cobalt tetracyanoethylene, Co(TCNE)x2010In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 17-18, p. 1892-1897Article in journal (Refereed)
    Abstract [en]

    V(TCNE)x, TCNE=tetracyanoethylene, x~2, is a semiconducting organicbased magnet and one of very few organic-based magnets with critical temperature above room temperature (RT). With the aim to understand the key design criteria for achieving RT organic-based magnets we have started to study the electronic and chemical structure of members of the M(TCNE)x family with significantly lower critical temperatures than V(TCNE)x. In this paper, Co(TCNE)x, x~2, (Tc~44 K, derived from its powder form) were prepared by a method based on physical vapor deposition, resulting in oxygen-free thin films. The results propose Co(TCNE)x to contain to local bonding disorder in contrast to V(TCNE)x thin films, which can be grown virtually defect free. In addition, the Co L-edge does not show any pronounced fine structure, suggesting the crystal field to be very weak. By using a variety of photoemission and X-ray absorption techniques the highest occupied molecular orbital (HOMO) of Co(TCNE)x was determined to mainly be TCNE-derived while the states originating from Co(3d) are localized at higher binding energies. This is in stark contrast to V(TCNE)x where V(3d) is mainly responsible for the HOMO. As the HOMO of Fe(TCNE)x (Tc~121 K, derived from its powder form) is TCNE-derived these results show that Co(TCNE)x is more similar to Fe(TCNE)x than to V(TCNE)x in terms of electronic structure.

  • 17.
    Chen, Miaoxiang
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Perzon, E.
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
    Robinson, Nathaniel D
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Jönsson, Stina
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Andersson, Mike
    Materials and Surface Chemistry, Chalmers University of Technology, Göteborg, Sweden.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Low band gap donor–acceptor–donor polymers for infra-red electroluminescence and transistors2004In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 146, no 3, p. 233-236Article in journal (Refereed)
    Abstract [en]

    We report on transistors and light-emitting diodes using a conjugated polymer consisting of alternated segments of fluorene units and low-band gap donor–acceptor–donor (D–A–D) units. The D–A–D segment includes two electron-donating thiophene rings combined with a thiadiazolo-quinoxaline unit, which is electron withdrawing to its nature. The resulting polymer is conjugated and has a band gap of around 1.27 eV. Here we present the corresponding electro- and photoluminescence spectra, which both peak at approximately 1 μm. Single layer light-emitting diodes demonstrated external quantum efficiencies from 0.03% to 0.05%. The polymer was employed as active material in thin film transistors, a field-effect mobility of 3 × 10−3 cm2/V s and current on/off ratio of 104 were achieved at ambient atmosphere.

  • 18.
    Cox, M.
    et al.
    Eindhoven University of Technology, Netherlands.
    Janssen, P.
    Eindhoven University of Technology, Netherlands.
    Wouters, S. H. W.
    Eindhoven University of Technology, Netherlands.
    van der Heijden, E. H. M.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands.
    The influence of device physics on organic magnetoresistance2013In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 173, p. 10-15Article in journal (Refereed)
    Abstract [en]

    In order to explain the surprisingly large, low field organic magnetoresistance (OMAR), several microscopic mechanisms have been proposed recently, but their effect on the polaron transport through a realistic device is relatively unknown. Here we study the effect of device physics on all proposed mechanisms, using a numerical drift-diffusion simulation method. We implement the local magnetic field dependent reactions via a magnetic field dependent recombination, mobility and triplet formation rate. Furthermore, a novel approach is used where we keep track of the subsequent particles formed from these reactions, including excitons and trions. We find that even in the most straightforward device structure sign changes can occur due to device physics. Especially the transition from a diffusion dominated to a drift dominated current near the built-in voltage plays a crucial role for understanding organic magnetoresistance. Finally, we conclude that the shape of the magnetocurrent as a function of voltage can be used as a fingerprint for the underlying dominant microscopic mechanism governing OMAR in a device. (c) 2012 Elsevier B.V. All rights reserved.

  • 19.
    Dannetun, P.
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lazzaroni, R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Scherr, E.
    Department of Chemistry, University of Pennsylvania Philadelphia, USA.
    Sun, Y.
    Department of Chemistry, University of Pennsylvania Philadelphia, USA.
    MacDiarmid, A. G.
    Department of Chemistry, University of Pennsylvania Philadelphia, USA.
    The eletronic structure of emeraldine doped in situ from HCl in the gas phase as studied by photoelectron spectroscopy1991In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 41, no 1-2, p. 645-648Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic structure of spin-coated films of polyaniline in the emeraldine state, treated in-situ with HCl in the gas phase, have been studied for the first time by means of X-ray Photoelectron Spectroscopy (XPS) and Ultra-violet Photoelectron Spectroscopy (UPS). Ultra thin films, of about several hundreds of Ångströms thickness, were spin-coated from a solution of chemically prepared emeraldine in NMP, onto substrates of aluminum or silicon. The salt forms were prepared both by (a) “wet” doping in 1M HCl and (b) the in-situ treatment of the films with HCl in the gas phase. With XPS three different types of chlorine have been observed, two ionic and one covalent. With UPS the valence band spectra of the doped and undoped state, are studied.

  • 20.
    Dannetun, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fauquet, C.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kaerijama, K.
    National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305, Japan.
    Sonoda, Y.
    National Institute of Materials and Chemical Research, Tsukuba, Ibaraki 305, Japan.
    Lazzaroni, R.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Brédas, J. L.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Interface formation between poly(2,5-diheptyl-p-phenylenevinylene) and calcium: implications for light-emitting diodes1994In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 67, no 1-3, p. 133-136Article in journal (Refereed)
    Abstract [en]

    The early stages of metal/polymer interface formation between calcium and poly(2,5-diheptyl-p-phenylenevinylene) (PDHPV) have been studied using both X-ray photoelectron spectroscopy and ultraviolet photoelectron spectroscopy. Charge transfer is observed from the metal atoms to the polymer; as a result the calcium atoms at the interface are ionic, and negative bipolarons appear as the charge-carrying species on the polymer chains. This n-type doping of PDHPV by calcium leads to the appearance of new electronic states in the polymer bandgap. The calcium atoms appear to diffuse into the near surface region of the polymer, rather than forming a well-defined overlayer on the organic films.

  • 21.
    Dannetun, Per
    et al.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Lögdlund, Michael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Boman, Magnus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Lazzaroni, R.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Mons Belgium.
    Fredriksson, C.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Mons Belgium.
    Brédas, J. L.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Mons Belgium.
    Graham, S.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Friend, R. H.
    Cavendish Laboratory, University of Cambridge, Cambridge, UK.
    Holmes, A. B.
    University Chemical Laboratory, Lensfield road, Cambridge, UK.
    Zamboni, R.
    Instituto di Spettroscopia Molecolare, Bologna, Italy.
    Taliani, C.
    Instituto di Spettroscopia Molecolare, Bologna, Italy.
    Proceedings of the International Conference on Science and Technology of Synthetic Metals The chemical and electronic structure of the interface between aluminum and conjugated polymers or molecules1993In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 55, no 1, p. 212-217Article in journal (Refereed)
    Abstract [en]

    The interaction between aluminum and α-ω-diphenyltetradecaheptaenee (DP7), α-sexithienyl (6T), and poly(p-phenylenevinylene) (PPV), respectively have been studied using both X-ray Photoelectron Spectroscopy (XPS) and Ultraviolet Photoelectron Spectroscopy (UPS). The UPS valence band spectra, are interpreted with the help of quantum chemical calculations based upon Modified Neglect of Diatomic Overlap (MNDO), Valence Effective Hamitonian (VEH) and ab initio Hartree-Fock methods. DP7 is a model molecule for polyacetylene, while 6T is a model molecule (an oligomer) of polythiophene. The results indicate that aluminum reacts strongly with the surfaces of all of the materials studied. The π-electronic structure of each material was strongly modified. Furthermore, aluminum reacts preferentially with the polyene partof DP7, with the vinylene part of PPV, and with the α-carbons of the thiophene nits of 6T.

  • 22.
    Dannetun, Per
    et al.
    Groupe de Physique des Solides, Tour 23-2, place Jussieu, 752 51 Paris Cedex 05, France.
    Lögdlund, Michael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fauquet, C.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Beljonne, D.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, place du Parc 20, B-7000 Mons, Belgium.
    Brédas, J. L.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, place du Parc 20, B-7000 Mons, Belgium.
    Bässler, H.
    Fachbereich Physikalische Chemie und Zentrum für Materialwissenschaften der Phillips-Universität, Hans-Meerwein-Strasse, W-3550 Marburg, Germany.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    The evolution of charge-induced gap states in degenerate and non-degenerate conjugated molecules and polymers as studied by photoelectron spectroscopy1994In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 67, no 1, p. 81-86Article in journal (Refereed)
    Abstract [en]

    We report the results of ultraviolet photoelectron spectroscopy (UPS) studies of the interaction between sodium and conjugated systems for a series of diphenylpolyees and diffrent oligomers of poly(p-phenylenevinylene) (PPV). The diphenylpolyenes include molecules containing two (i.e., stilbene) to 14 carbon atoms in the polyene part; stilbene itself can also be considered as a phenyl-capped monomer of PPV. Furthermore, a PPV oligomer with three phenylene units, as well as PPV itself, has been studied. The experimental results are interpreted with the help of quantum-chemical calculations using the Hartree-Fock semi-empirical Austin Model 1 (AM1) and valence-effective Hamiltonian (VEH) methods. An important result is that all the systems react strongly with sodium; at high doping levels two new doping-induced states are detected above the valence band edge of the pristine material. In the case of saturation-doped diphenylpolyenes (i.e., two sodiums per molecule), the new states can be discussed in terms of soliton-antisoliton pairs confined within the polyene part of the molecules; in contrast, the self-localized states induced in PPV and its oligomers have to be referred to as bipolarons.

  • 23. Ding, L.
    et al.
    Jonforsen, M.
    Department of Polymer Technology, Chalmers Univ. of Technol., S-41296, Göteborg, Sweden.
    Roman, L.S.
    Andersson, M.R.
    Department of Polymer Technology, Chalmers Univ. of Technol., S-41296, Göteborg, Sweden.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Photovoltaic cells with a conjugated polyelectrolyte2000In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 110, no 2, p. 133-140Article in journal (Refereed)
    Abstract [en]

    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.

  • 24. Eriksson, A
    et al.
    Bertilsson, K
    Swedish Def Res Agcy, FOI, SE-58111 Linkoping, Sweden.
    Lindgren, M
    Simulation of beam propagation with time-dependent nonlinear processes in optical limiting applications2002In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 127, no 1-3, p. 147-150Article in journal (Refereed)
    Abstract [en]

    A scheme based on the Cranck-Nicholson model has been realized in Matlab code and used to simulate the intensity propagation of various temporal pulse shapes through optically nonlinear materials. The differential equations associated with three- and five-level systems were solved numerically in each point over the active time-space grid. Instantaneous two-photon absorption and dynamic multilevel systems, one at the time, or in combination, can be used to model material responses. A typical Rayleigh length was 0.5 mm. and a pulse length up to a few nanometers for sample lengths of typically 2 mm. (C) 2002 Elsevier Science B.V. All rights reserved.

  • 25.
    Fredriksson, C.
    et al.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Lazzaroni, R.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Bredas, J. L.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Dannetun, Per
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Lögdlund, Michael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Theoretical studies of the aluminum/poly(p-phenylene vinylene) interface1993In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 57, no 2, p. 4632-4637Article in journal (Refereed)
    Abstract [en]

    A molecular quantum chemical approach is used to study the aluminum on PPV (Poly(p-Phenylene Vinylene)) interface. We focus on modifications to the chemical and electronic structure of the polymer upon interaction with a submonolayer of aluminum. A model system, trans-stilbene, is taken to investigate the nature of the Al-PPV bonding. Energetically favorable conformations are then used as prototypes to study the evolution of the electronic structure as modified by the reaction with aluminum. Results at the ab initio Hartree-Fock level indicates that Al atoms react with the vinylene linkage rather than the phenyl groups at early stages of interface formation.

  • 26.
    Fredriksson, C.
    et al.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Lazzaroni, R.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Bredas, J. L.
    Service de Chimie des Matériaux Nouveaux, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Dannetun, Per
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Lögdlund, Michael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Theoretical studies of the aluminum/trans-polyacetylene interface: Calculations of model systems and comparison to experiment1993In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 57, no 2-3, p. 4590-4595Article in journal (Refereed)
    Abstract [en]

    The interaction between Al atoms and trans-polyacetylene has been studied quantum chemically at the ab initio Hartree-Fock level using oligomeric model systems. Investigations of the Al-polyacetylene bonding and modifications to the chemical and electronic structure of model systems for polyacetylene upon interaction with Al atoms are reported. The density-of-states is calculated for a polyene chain interacting with a pair of Al atoms. The results are discussed in relation to photoelectron spectra taken during Al deposition on an oligomeric model for polyacetylene (a diphenylpolyene with 7 C=C bonds in the polyene segment).

  • 27.
    Friedlein, Rainer
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Crispin, Xavier
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Braun, Slawomir
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    de Jong, Michel P
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Simpson, CD
    Watson, MD
    von Kieseritzky, F
    Samori, P
    Jonsson, SKM
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Jackel, F
    Rabe, JP
    Hellberg, J
    Mullen, K
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Surface-induced vertical alignment of self-assembled supramolecular columns of large polycyclic aromatic hydrocarbons and porphyrins2004In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 147, no 01-Mar, p. 79-83Article in journal (Refereed)
    Abstract [en]

    Ordered films of polycyclic aromatic hydrocarbons (PAHs) and porphyrins with functional (e.g. thiophene) side-groups are good candidates for (opto-)electronic applications where fast charge separation and transport are required. Such highly ordered thin films of PAHs, including discotic hexa-peri-hexabenzocoronene (HBC) and C-132-C-16,C-4, as well as brominated functionalized porphyrin molecules have been grown from solutions on semi-metallic molybdenum disulfide substrates and characterized by angle-resolved valence band photoelectron spectroscopy. A vertical growth of self-assembled supramolecular columns perpendicular to the basal plane of the substrate along with their lateral ordering on the surface has been achieved. Annealing made it possible to increase the structural order in the HBC columns, with molecules positioned at a regular offset from the columnar axis. This permitted the formation of extended pi-electronic states with a bandwidth of at least 0.1-0.2 eV at room temperature. (C) 2004 Elsevier B.V. All rights reserved.

  • 28.
    Gadisa, Abay
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Tvingstedt, Kristofer
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Admassie, Shimelis
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lindell, Linda
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Department of Organic Chemistry and Polymer Technology, Chalmers University of Technology, Göteborg, Sweden.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics . Linköping University, The Institute of Technology.
    Transparent polymer cathode for organic photovoltaic devices2006In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 156, no 16-17, p. 1102-1107Article in journal (Refereed)
    Abstract [en]

    We demonstrate a prototype solar cell with a transparent polymer cathode, and indium-tin-oxide (ITO)/poly (3, 4-ethylene dioxythiophene)-poly (styrene sulphonate) (PEDOT:PSS) anode. As an active layer, thin film of a bulk heterojunction of polyfluorene copolymer poly[2,7-(9,9-dioctyl-fluorene)-alt-5,5-(4′,7′-di-2thienyl-2′,1′3′-benzothiadiazole)] (APFO-3) and an electron acceptor molecule [6] and [6]-phenyl-C61-butyric acid methyl ester (PCBM) (1:4 wt.) was sandwiched between the two transparent polymer electrodes. The cathode is another form of PEDOT formed by vapor phase polymerised PEDOT (VPP PEDOT) of conductivity 102–103 S/cm. The cathode is supported on an elastomeric substrate, and forms a conformal contact to the APFO-3/PCBM blend. Transparent solar cells are useful for building multilayer and tandem solar cells.

  • 29. Ghosh, S.
    et al.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Nano-structured conducting polymer network based on PEDOT-PSS2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 121, no 1-3, p. 1321-1322Article in journal (Refereed)
    Abstract [en]

    Poly(3,4-ethylenedioxythiophene)-polystyrenesulphonate (PEDOT-PSS) has been crosslinked into network morphology. The morphologies of different crosslinked PEDOT-PSS firms have been characterised by atomic force microscopy (AFM). The crosslinked polymer shows highly efficient and fast redox activity, both in aqueous and non-aqueous media.

  • 30.
    Gigli, G.
    et al.
    Applied Physics, Department of Physics (IFM), Linkoping University, S-581 83 Linkoping, Sweden.
    Anni, M.
    INFM, Universita' di Lecce, Dipto. di I., Via Arnesano, 73100 Lecce, Italy.
    Theander, M.
    Applied Physics, Department of Physics (IFM), Linkoping University, S-581 83 Linkoping, Sweden.
    Cingolani, R.
    INFM, Universita' di Lecce, Dipto. di I., Via Arnesano, 73100 Lecce, Italy.
    Barbarella, G.
    CNR Bologna, ICoCEA, Via Gobetti 10, I-40129 Bologna, Italy.
    Favaretto, L.
    CNR Bologna, ICoCEA, Via Gobetti 10, I-40129 Bologna, Italy.
    Inganas, O.
    Inganäs, O., Applied Physics, Department of Physics (IFM), Linkoping University, S-581 83 Linkoping, Sweden.
    A novel electroluminescent oligothiophene2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 119, no 1-3, p. 581-582Article in journal (Refereed)
    Abstract [en]

    We report investigations of the photoluminescence (PL) and electroluminescence (EL) of a novel substituted thiophene oligomer. The high PL efficiency in solid state (23%), the high electron affinity, together with the good processability make this material competitive for applications in organic emitting diodes (LEDs). EL efficiency of 0.1% is demonstrated in a stable LED with spin coated active layer.

  • 31.
    Granlund, Thomas
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Theander, Mathias
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, Mats
    Chalmers Tekniska Högskola.
    Ruzeckas, A
    Lunds universitet.
    Sundström, V
    Lunds universitet.
    Björk, G
    KTH.
    Granström, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Lasing in substituted polythiophene between dielectric mirrors1999In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 102, no 1-3, p. 1038-1041Article in journal (Refereed)
    Abstract [en]

    We report photopumped lasing in a microcavity device with a polythiophene layer as emitter. The microcavity is made of a polymer film between two dielectric Bragg reflecting mirrors (DBR). The:microcavity devices is built by joining two polymer coated DBR mirrors at elevated temperature. When photopumping the film,a lasing threshold is observed at 120 nJ/cm(2). Comparative studies with fast pump-probe spectroscopy of thin polythiophene films, and the same polymer in photopumped lasing studies, indicate that the gain coefficient is 80 +/- 20 cm(2) and that the exciton concentration is 2X10(17) cm(2) at the lasing transition, well below the exciton-exciton recombination level.

  • 32.
    Granström, Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Polymeric light-emitting diodes of submicron size - Structures and developments1996In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 76, no 1-3, p. 141-143Article in journal (Refereed)
    Abstract [en]

    Micron- and submicron-sized light-emitting diodes (LEDs) made using conjugated polymers as electroluminescent layers and contact materials are presented. Two different routes to make arrays of such small light sources have been developed. The benefits and drawbacks of the use of the conjugated polymer poly(2,3-ethylene-dioxythiophene) (PEDOT) as hole injector in polymer LEDs are also discussed.

  • 33.
    Granström, Magnus
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Hjertberg, T.
    Chalmers Tekniska Högskola.
    Wennerström, O.
    Chalmers Tekniska Högskola.
    Phase separation of conjugated polymers - Tools for new functions in polymer LEDs1997In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 85, no 1-3, p. 1193-1194Article in journal (Refereed)
    Abstract [en]

    Within the single family of substituted poly(thiophenes) it is possible to realize such diverse device designs as voltage controlled colours from polymer LEDs, sub-micron size LEDs, and white light emitters. Many of these features become possible by the use of polymer blends in which one or more poly(thiophenes) are mixed with a matrix polymer (PMMA). The phase structure in these blends can be controlled by stoichiometry and mode of formation. That phase structure can be used to prevent exciton transfer, and to define new colours in polymer LEDs. It also allows us to make anisotropic conductors suitable for contacting optical devices.

  • 34. Greczynski, G.
    et al.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Hybrid interfaces in polymer-based electronics2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 121, no 1-3, p. 1625-1628Article in journal (Refereed)
    Abstract [en]

    Sandwich-style interfaces of Al/LiF/poly(9,9-dioctyl-fluorene) and A1/CsF/poly(9,9-dioctyl-fluorene) have been studied using X-ray and ultraviolet photoelectron spectroscopy. In the case of LiF-deposition on poly(9,9-dioctyl-fluorene) films, doping did not occur, nor did the LiF dissociate upon Al-deposition. No significant shifts in binding energy of the core levels, or any changes in the work function were detected. However, for the Al/LiF/poly(9,9-dioctyl-fluorene) interface, there was no degradation of the p-electronic structure, unlike the case for Al deposited directly unto poly(9,9-dioctyl-fluorene). For the Al/CsF/poly(9,9-dioctyl-fluorene) interface, the CsF dissociated upon Al deposition, with the Cs likely n-doping the polymer at the interface. When deposited onto an Al surface, CsF also was found to dissociate at the interface but remaining in the CsF form away from the Al surface. Vacuum level alignment occurs for poly(9,9-dioctyl-fluorene) films spun onto 'metal' substrates. The hole-injection barrier in poly(9,9-dioctyl-fluorene)-based LEDs is hence determined by the difference between anode work function and the polymer ionization potential.

  • 35. Hjort, M.
    et al.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Localization in defected chiral carbon nanotubes2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 121, no 1-3, p. 1239-1240Article in journal (Refereed)
    Abstract [en]

    Defects in metallic carbon nanotubes have been studied within the tight binding model using the transfer matrix approach. A newly developed method for obtaining transfer matrices in a general way has been utilized, enabling us to compare nanotubes with various chiralities. The localization length was calculated for a random disorder in the onsite potentials, as well as for a functionalization type of disorder.

  • 36.
    Inganäs, Olle
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Gustafsson, Göran
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Hjertberg, T.
    Chalmers Tekniska Högskola.
    Wennerström, O.
    Chalmers Tekniska Högskola.
    Dyreklev, Peter
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Granström, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Thiophene polymers in light emitting diodes: Making multicolour devices1995In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 71, no 1-3, p. 2121-2124Article in journal (Refereed)
    Abstract [en]

    We can control the bandgap of thiophene polymers over 2 eV by choosing the nature, position and regularity of side chain substitutions. Electroluminescence from these polymers cover the full visible spectrum, from the blue into the near infra-red. Blends of these polymer materials allow us to construct voltage controlled variable colour light sources. A newly developed transfer technique allow us to mount thin oriented films of the polymers in polymer LEDs to obtain polarised light sources giving polarisation anisotropys of up to 3. Sub-lambda light sources have been constructed from these polymer materials using nanometer polymer electrodes.

  • 37.
    Inganäs, Olle
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Roman, L.S.
    Zhang, Fengling
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Johansson, D.M.
    Department of Polymer Technology, Chalmers University of Technology, S-412 96 Göteborg, Sweden.
    Andersson, M.R.
    Department of Polymer Technology, Chalmers University of Technology, S-412 96 Göteborg, Sweden.
    Hummelen, J.C.
    Stratingh Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, Netherlands.
    Recent progress in thin film organic photodiodes2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 121, no 1-3, p. 1525-1528Article in journal (Refereed)
    Abstract [en]

    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.

  • 38.
    Jager, Edwin
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Smela, Elisabeth
    Condensed Matter Department, Risö National Lab.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Lundström, Ingemar
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics . Linköping University, The Institute of Technology.
    Polypyrrole micro actuators1999In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 102, no 1-3, p. 1309-1310Article in journal (Refereed)
    Abstract [en]

    The doping and undoping of conjugated polymers is accompanied by a volume change. This volume change can be used to make micro-actuators. We have built polypyrrole (PPy) gold bilayer structures. The volume change of PPy induces a bending of the bilayer. We have made micro-actuators based on this principle, which have been examined with video-microscopy. Some applications for these microactuators are proposed, including opening and closing boxes for cell biology and nanoliter chemistry and micro-robotics.

  • 39.
    Janssen, P.
    et al.
    Eindhoven University of Technology, Netherlands.
    Wagemans, W.
    Eindhoven University of Technology, Netherlands.
    Verhoeven, W.
    Eindhoven University of Technology, Netherlands.
    van der Heijden, E. H. M.
    Eindhoven University of Technology, Netherlands.
    Kemerink, M.
    Eindhoven University of Technology, Netherlands.
    Koopmans, B.
    Eindhoven University of Technology, Netherlands.
    On the role of minority carriers in the frequency dependence of organic magnetoresistance2011In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 161, no 7-8, p. 617-621Article in journal (Refereed)
    Abstract [en]

    In this work we investigate the frequency dependence of organic magnetoresistance (OMAR) both in small molecule-based (Alq3) and polymer (PPV derivative) materials, and investigate its thickness dependence. For all devices, we observed a strong decrease in magnetoconductance (MC) with increasing frequency of the ac component of the applied magnetic field. Moreover, we observed a strong reduction of the cut-off frequencies for increasing film thickness. By means of admittance spectroscopy and device simulations, we show that the cut-off frequency is related to the inverse transit time of the minority charge carriers. These observations confirm the important role of minority carriers in OMAR, and show that changes in OMAR are not only due to microscopic mechanisms, but also device physics is of significant relevance. (C) 2011 Elsevier B.V. All rights reserved.

  • 40. Johansson, A.
    et al.
    Stafström, Sven
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Computational Physics .
    Polaron dynamics in a system of coupled conjugated polymer chains2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 119, no 1-3, p. 235-236Article in journal (Refereed)
    Abstract [en]

    Motion of excitations such as solitons and polarons are of fundamental importance for the electron/hole transport properties of conjugated polymers for the use in, e.g., polymer based LED's. Polaron dynamics in coupled polymer chains in the presence of an external electric field, has been investigated theoretically using the SSH-model. In particular we focus on how a polaron migrates through the polymer lattice, i.e. the situation in which a polaron reaches a chain end and is scattered to the surrounding chains.

  • 41.
    Johansson, D.M.
    et al.
    Department of Organic Chemistry, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
    Granlund, T.
    Theander, M.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, M.R.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
    Synthesis and characterisation of polyfluorenes with light-emitting segments2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 121, no 1-3, p. 1761-1762Article in journal (Refereed)
    Abstract [en]

    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.

  • 42.
    Johansson, D.M.
    et al.
    Department of Organic Chemistry, Chalmers Univ. Technol., SE-412 96, Göteborg, Sweden.
    Theander, M.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, M.R.
    Department of Polymer Technology, Chalmers Univ. Technol., SE-412 96, Göteborg, Sweden.
    Convenient synthetic route to poly(p-phenylene-1,2-diphenylvinylenes)2000In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 113, no 3, p. 293-297Article in journal (Refereed)
    Abstract [en]

    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.

  • 43.
    Johansson, E.
    et al.
    Department of Physics, University of Uppsala, Uppsala, Sweden.
    Sandell, A.
    Department of Physics, University of Uppsala, Uppsala, Sweden.
    Siegbahn, H.
    Department of Physics, University of Uppsala, Uppsala, Sweden.
    Rensmo, H.
    Department of Physics, University of Uppsala, Uppsala, Sweden.
    Mahrov, B.
    Department of Physics and Physical Chemistry, University of Uppsala, Uppsala, Sweden.
    Boschloo, G.
    Department of Physical Chemistry, University of Uppsala, Uppsala, Sweden.
    Figgemeier, E.
    Department of Physical Chemistry, University of Uppsala, Uppsala, Sweden.
    Hagfeldt, A.
    Department of Physical Chemistry, University of Uppsala, Uppsala, Sweden.
    Jönsson, Stina
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Interfacial properties of photovoltaic TiO2/dye/PEDOT–PSS heterojunctions2005In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 149, no 2-3, p. 157-167Article in journal (Refereed)
    Abstract [en]

    Systems comprising a dense TiO2 film electrode, a ruthenium polypyridine dye and a PEDOT–PSS (poly(3,4-ethylenedioxythiophene)–poly(4-styrenesulphonate)) film were prepared. The heterojunctions were shown to have photovoltaic properties, with the dye absorbing the light, the TiO2 acting as an electron conducting material and PEDOT–PSS acting as a hole transport material. A series of dyes was used to investigate their influence on the photocurrent and the photovoltage characteristics of the heterojunction. These results were compared to a photoelectrochemical system in which the PEDOT–PSS was replaced by a liquid electrolyte containing triiodide/iodide redox-couple.

    Photoelectron spectroscopy (PES) was used to monitor the interfacial properties of the heterojunction and the investigation points out effects of importance when assembling the materials together to a functional unit. Specifically, it was concluded that the interaction with the dye clearly affects the structure of PEDOT–PSS, both with respect to the surface composition of PSS relative to PEDOT and with respect to the chemical state of the sulphur in the polymers. Moreover, a comparison of the Ru3d and the valence band spectra of the two different interfaces (dye/TiO2 and dye/PEDOT–PSS) indicates that the energy level structure of the dyes compared to the substrate is different for the two surfaces. Thus, in the combined energy level picture under dark conditions, the energy levels in TiO2 relative to the energy levels in PEDOT–PSS depend on the dye.

  • 44.
    Johansson, Tomas
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Pettersson, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Conductivity of de-doped poly(3,4-ethylenedioxythiophene)2002In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 129, no 3, p. 269-274Article in journal (Refereed)
    Abstract [en]

    The conductivity of chemically and electrochemically de-doped poly(3,4-ethylenedioxythiophene) (PEDOT) has been investigated in situ. We observe a decrease in the conductivity by 4-5 orders of magnitude. The change of conductivity is correlated to the change of electronic structure. We obtain the dielectric function of the polymer by spectroscopic ellipsometry and note that anisotropy is observed in both doped and neutral states. © 2002 Elsevier Science B.V. All rights reserved.

  • 45.
    Jonforsen, M.
    et al.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Ahmad, I.
    Johansson, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Larsson, J.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Roman, L.S.
    Svensson, M.
    Department of Organic Chemistry, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, M.R.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Gothenburg, Sweden.
    Photodiodes made from poly(pyridopyrazine vinylene): polythiophene blends2001In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 119, no 1-3, p. 185-186Article in journal (Refereed)
    Abstract [en]

    A PPV-type polymer with the pyridopyrazine heterocycle (EHH-PPyPzV) has been synthesised and found to have high electron affinity according to electrochemical measurements. When used as the electron accepting material in single-layer-photodiodes, with a thiophene copolymer (PEOPT-co-PAAPT) as the electron donating material, IPCE (incident photon to current conversion efficiency) up to 1% was measured. Atomic force microscopy was used to analyse the blend morphology in the devices.

  • 46.
    Jonforsen, M.
    et al.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
    Johansson, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Spjuth, L.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Andersson, M.R.
    Department of Polymer Technology, Chalmers University of Technology, SE-412 96 Göteborg, Sweden.
    Synthesis and characterization of poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with phenyl substituted side-groups2002In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 131, no 1-3, p. 53-59Article in journal (Refereed)
    Abstract [en]

    Poly(quinoxaline vinylene) and poly(pyridopyrazine vinylene) with 3(2'-ethylhexyloxy)phenyl side-groups have been synthesized and compared with similar polymers with purely aliphatic side-chains. The new polymers had smaller bandgaps, and from cyclic voltammetry it was seen that the phenyl substituted side-groups made the polymers easier to reduce, with half wave potentials of -1.02 and -1.33 V versus Ag/AgCl for the poly(pyridopyrazine vinylene) and poly(quinoxaline vinylene) respectively. The attachment of the phenyl substituted side-groups had counteracting effects on the stability towards photo-oxidation, which resulted in improved stability of the poly(pyridopyrazine vinylene) compared to its equivalent with purely aliphatic side-chains, while the poly(quinoxaline vinylene) showed decreased stability. © 2002 Elsevier Science B.V. All rights reserved.

  • 47.
    Jönsson, Stina
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Birgerson, J.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Greczynski, Grzegorz
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Osikowicz, Wojciech
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Denier van der Gon, A.W.
    Denier van der Gon, A.W., Faculty of Applied Physics, Eindhoven University of Technology, Eindhoven, Netherlands.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    The effects of solvents on the morphology and sheet resistance in poly(3,4-ethylenedioxythiophene)–polystyrenesulfonic acid (PEDOT–PSS) films2003In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 139, no 1, p. 1-10Article in journal (Refereed)
    Abstract [en]

    Films of poly(3,4-ethylenedioxythiophene)–polystyrenesulfonic acid (PEDOT–PSS), prepared by coating the aqueous PEDOT–PSS dispersion and by coating a mixture of the PEDOT–PSS dispersion and different solvents, have been studied using four-point probe conductivity measurements, atomic force microscopy and photoelectron spectroscopy. The electrical conductivity of thin films of the second type (further on called PEDOT–PSS–solvents) was increased by a factor of about 600 as compared to films of the first type (further on called PEDOT–PSS–pristine). Morphological and physical changes occur in the polymer film due to the presence of the solvent mixture, the most striking being that the ratio of PEDOT-to-PSS in the surface region of the films is increased by a factor of ∼2–3. This increase of PEDOT at the surface indicates that the thickness of the insulating PSS ‘shell’ that surrounds the conducting PEDOT–PSS grains is reduced. The (partial) reduction of the excess PSS layer that surrounds the conducting PEDOT–PSS grains is proposed to lead to an increased and improved connectivity between such grains in the film and hence a higher conductivity. When PEDOT–PSS–solvents receives a post-coating heat treatment, the increased PEDOT-to-PSS ratio at the surface is maintained or even slightly improved, as is the increase in electrical conductivity, even though spectroscopy show that the solvent molecules are removed. This suggests that screening or doping by the solvents throughout the film are not likely to be the key mechanisms for the improved conductivity and supports our proposed mechanism of improved conductivity through improved connectivity between the conducting grains.

  • 48.
    Kaminorz, Y.
    et al.
    Institute of Physics, Condensed Matter Phys., Univ. P., Potsdam, Germany.
    Smela, E.
    Condensed Matter Phys. Chem. Dept., Ris Natl. Lab. FYS-124, P.O. B., Roskilde, Denmark.
    Johansson, Tomas
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Brehmer, L.
    Institute of Physics, Condensed Matter Phys., Univ. P., Potsdam, Germany.
    Andersson, M.R.
    Dept. Organ. Chem. Poly. Technol., Chalmers Univ. of Technol., S-412 96, Göteborg, Sweden.
    Inganäs, Olle
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics .
    Characteristics of polythiophene surface light emitting diodes2000In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 113, no 1, p. 103-114Article in journal (Refereed)
    Abstract [en]

    Surface light emitting diodes (SLEDs), in which previously microfabricated electrodes were coated with a conjugated polymer, were made with greatly different electrode spacings (250 nm and 10 or 20 µm) and with different electrode material combinations. The fabrication process allowed us to compare several electrode materials. The SLED structures also enabled imaging of the light emission zone with fluorescence video microscopy. Conventional sandwich structures were also made for comparison (electrode separation 50 nm). In this study, the emitting layer was poly[3-(2',5'-bis(1?,4?,7?trioxaoctyl)phenyl)- 2,2'-bithiophene] (EO-PT), a conjugated polymer based on polythiophene with oligo(ethyleneoxide) side chains. The current-voltage (I(V)) and light-voltage (L(V)) characteristics of the SLEDs were largely insensitive to electrode separation except at high voltages, at which the current in the devices with the largest separations was limited. Sandwich structures had the same light output at a given current. Light could be obtained in forward and reverse bias from indium tin oxide (ITO)-aluminum, gold silicide-aluminum, and gold silicide-gold SLEDs, but the turn-on voltages were lowest with the ITO-aluminum devices, and these were also the brightest and most reliable. Adding salt to the EO-PT increased the current and brightness, decreased the turn-on voltages, and made the I(V) characteristics symmetric, thus, a device with an electrode separation of 10 µm had the extraordinarily low turn-on voltage of 6 V. The location of the light emission was at the electron-injecting contact.

  • 49.
    Kim, J.S.
    et al.
    Cavendish Laboratory, Dept. Phys., Univ. Cambridge, M., Cambridge, United Kingdom.
    Lagel, B.
    Lägel, B., Department of Physics, Robert Gordon University, Aberdeen, United Kingdom.
    Moons, E.
    Cavendish Laboratory, Dept. Phys., Univ. Cambridge, M., Cambridge, United Kingdom.
    Johansson, N.
    Baikie, I.D.
    Department of Physics, Robert Gordon University, Aberdeen, United Kingdom.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Friend, R.H.
    Cavendish Laboratory, Dept. Phys., Univ. Cambridge, M., Cambridge, United Kingdom.
    Cacialli, F.
    Cavendish Laboratory, Dept. Phys., Univ. Cambridge, M., Cambridge, United Kingdom.
    Kelvin probe and ultraviolet photoemission measurements of indium tin oxide work function: a comparison2000In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 111, p. 311-314Article in journal (Refereed)
    Abstract [en]

    We report a comparison of the work functions of thin films of indium tin oxide (ITO), carried out by means of ultraviolet photoelectron spectroscopy (UPS) and by measurements of the contact potential difference with respect to a gold reference electrode (Kelvin probe (KP) method). We investigated commercially available ITOs both 'as-received', and after certain surface treatments, such as oxygen plasma. First, we find measurable discrepancies between KP values measured with three different instruments, and between the KP and the UPS values. Secondly, and unexpectedly, we find that the KP, although more sensitive than UPS, does not detect certain differences between ITOs with different surface treatments. We discuss the results in view of the different environments in which the measurements are carried out (UHV for the UPS and air/Ar for the Kelvin method), of the effects which may be induced by the high-energy photon irradiation in the UPS measurement, and of the stability of the gold probe work function in gas ambient. We conclude that UPS is better-suited for absolute work function determination, although KP remains a convenient and inexpensive tool for fast screening of contact potential differences.

  • 50.
    Lazzaroni, R.
    et al.
    Service de Chimie des Matériaux Nouveaux, Département des Matériaux et Procédés, Université de Mons-Hainaut, Belgium.
    Brédas, J. L.
    Service de Chimie des Matériaux Nouveaux, Département des Matériaux et Procédés, Université de Mons-Hainaut, Belgium.
    Dannetun, Per
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Lögdlund, Michael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Electronic structure of the aluminum/polythiophene interface: A joint experimental and theoretical study1991In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 43, no 1-2, p. 3323-3328Article in journal (Refereed)
    Abstract [en]

    Not Available.

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