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  • 151.
    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.

  • 152.
    Osikowicz, Wojciech
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Van, Der Gon A.W.D.
    Van Der Gon, A.W.D., Department of Applied Physics, Eindhoven Univ. of Technology, PO Box 513, 5600 MB Eindhoven, Netherlands.
    Crispin, Xavier
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    de Jong, Michel P
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Friedlein, Rainer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Groenendaal, L.
    AGFA-Gevaert N.V., R and D Mat. - Chem. Dept., Septestraat 27, B-2640 Mortsel, Belgium.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Beljonne, D.
    Serv. Chim. des Materiaux Nouveaux, CREPM, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Lazzaroni, R.
    Serv. Chim. des Materiaux Nouveaux, CREPM, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    A joint theoretical and experimental study on the electronic properties of phenyl-capped 3,4-ethylenedioxythiophene oligomers2003In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 119, no 19, p. 10415-10420Article in journal (Refereed)
    Abstract [en]

    The electronic structure of a series of phenyl-capped EDOT oligomers was studied using ultraviolet photoelectron spectroscopy, in combination with quantum-chemical methods. The bulk IP of the neutral PEDOT polymer was estimated to be 4.2 eV. The frontier band structue was predicted from the evolution of the spectral features in the studied series of oligomers.

  • 153.
    Crispin, Xavier
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Marciniak, S.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Osikowicz, Wojciech
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Zotti, G.
    Instituto Consiglio Nazionale delle Ricerche per l' Energetica e le Interfasi, Padova, Italy.
    Denier Van Der Gon, A. W.
    Faculty of Applied Physics, Eindhoven University of Technology, Eindhoven, The Netherlands.
    Louwet, F.
    Chemistry Department, R&D Materials Research, Agfa Gevaert N.V., Mortsel, Belgium.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Groenendaal, L.
    Chemistry Department, R&D Materials Research, Agfa Gevaert N.V., Mortsel, Belgium.
    De Schryver, F.
    Afdeling Fotochemie en Spectroscopie, Katholieke Universiteit Leuven, Heverlee, Belgium.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, The Institute of Technology.
    Conductivity, Morphology, Interfacial Chemistry, and Stability of Poly(3,4- ethylene dioxythiophene)–Poly(styrene sulfonate): A Photoelectron Spectroscopy Study2003In: Journal of Polymer Science Part B: Polymer Physics, ISSN 0887-6266, E-ISSN 1099-0488, Vol. 41, no 21, p. 2561-2583Article, review/survey (Refereed)
    Abstract [en]

    X-ray photoelectron spectroscopy (XPS) has been used to characterize poly(3,4-ethylene dioxythiophene)-poly(styrene sulfonate) (PEDT/PSS), one of the most common electrically conducting organic polymers. A correlation has been established between the composition, morphology, and polymerization mechanism, on the one hand, and the electric conductivity of PEDT/PSS, on the other hand. XPS has been used to identify interfacial reactions occurring at the polymer-on-ITO and polymer-on-glass interfaces, as well as chemical changes within the polymer blend induced by electrical stress and exposure to ultraviolet light.

  • 154.
    Zotti, G.
    et al.
    Istituto CNR l'Energetica Interfasi, C.o Stati Uniti 4, 35127 Padova, Italy.
    Zecchin, S.
    Istituto CNR l'Energetica Interfasi, C.o Stati Uniti 4, 35127 Padova, Italy.
    Schiavon, G.
    Istituto CNR l'Energetica Interfasi, C.o Stati Uniti 4, 35127 Padova, Italy.
    Louwet, F.
    R and D Materials Research, Chemistry Department, Agfa Gevaert N.V., Septelaan 27, B-2640 Mortsel, Belgium.
    Groenendaal, L.
    R and D Materials Research, Chemistry Department, Agfa Gevaert N.V., Septelaan 27, B-2640 Mortsel, Belgium.
    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 .
    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 .
    Electrochemical and XPS studies toward the role of monomeric and polymeric sulfonate counterions in the synthesis, composition, and properties of poly(3,4-ethylenedioxythiophene)2003In: Macromolecules, ISSN 0024-9297, E-ISSN 1520-5835, Vol. 36, no 9, p. 3337-3344Article in journal (Refereed)
    Abstract [en]

    Electrochemically prepared poly(3,4-ethylenedioxythiophene) (PEDT) poly(styrenesulfonate) (PSS), produced from acidic (PSSH) and basic (PSSNa) PSS, was characterized by cyclic voltammetry CV, UV-vis spectroscopy, in situ conductivity, and XPS spectroscopy and was compared with electrochemically prepared PEDT/tosylate and chemically prepared PEDT/PSS. CV analysis shows that the polymer synthesis is strongly affected by the nucleophilic character of the counteranion. Although CV and UV-vis spectroscopy show that the structure and degree of polymerization (oligomeric, ca. 10 EDT units) of the PEDT backbone is the same for all polymers, XPS is able to explain the different conductivity values for these materials (ranging from 1 S cm-1 for PEDT/PSSNa to 400-450 S cm-1 for PEDT/tosylate) based on doping level and composition. In particular, critical results are observed to be the ratios between sulfonate and thiophene units in the polymers: the higher the PEDT concentration, the higher the conductivity. XPS also explains by solvent-induced nanometer-scale segregation between PEDT/PSS and excess PSS particles the often reported conductivity enhancement of chemically prepared PEDT/PSS upon treatment with polar solvents.

  • 155.
    Wong, K.Y.
    et al.
    Wong, K.Y..
    Smallfield, J.A.O.
    Smallfield, J.A.O..
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Epstein, A.J.
    Epstein, A.J..
    Electronic state of nitrogen containing polypyridine at the interfaces with model sulfonic acid containing polymer and molecule2003Conference paper (Refereed)
    Abstract [en]

    We present results of an X-ray photoelectron spectroscopy (XPS) study of the interfaces between polypyridine (PPy) and model sulfonic acid containing polymer and molecule. We show that the N 1s level splits reflecting protonation of a substantial fraction of the PPy N sites. Density functional theory (DFT) is employed to compare excitation energies, bond angles, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and density of states of oligomers of pyridine and protonated pyridine. These results are in accord with the proposed origin of the red shift of the emitted light under forward bias in color-variable alternating-current light emitting (SCALE) devices.

  • 156.
    Friedlein, Rainer
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Sorensen, S.L.
    Sörensen, S.L., Department of Synchrotron Radiation Research, Institute of Physics, Lund University, S-221 00 Lund, Sweden.
    Osikowicz, Wojciech
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Rosenqvist, L.
    Department of Synchrotron Radiation Research, Institute of Physics, Lund University, S-221 00 Lund, Sweden.
    Crispin, Annica
    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.
    de Jong, Michel P
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Murphy, C.
    CDT Ltd., Cambridge CB3 0KJ, United Kingdom.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electronic structure of conjugated polymers and interfaces in polymer-based electronics2003Conference paper (Refereed)
    Abstract [en]

    The electronic structure of conjugated polymers and interfaces in polymer-based electronics were analyzed. Fine structure were observed in the region of the first resonance with pi-final state symmetry, between 284.1 eV and 285.8 eV. The electronic transitions from the non-dispersed C(1s) level to specific parts of the unoccupied band structure were generated. It was found that for a dispersing valence band, in the presence of a core-hole, a given photon energy corresponded to an excitation into a state with a distinct wave vectors.

  • 157.
    Friedlein, Rainer
    et al.
    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, Department of Science and Technology. Linköping University, The Institute of Technology.
    Simpson, C. D.
    Max Planck Institute for Polymer Research, Germany.
    Watson, M. D.
    Max Planck Institute for Polymer Research, Germany.
    Jackel, F.
    Department of Physics, Humboldt University Berlin, Berlin, Germany.
    Osikowicz, Wojciech
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Marciniak, S.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    de Jong, Michel P
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Samori, P.
    Department of Physics, Humboldt University Berlin, Berlin, Germany.
    Jönsson, Stina
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry.
    Müllen, K.
    Max Planck Institute for Polymer Research, Germany.
    Rabe, J. P.
    Department of Physics, Humboldt University Berlin, Berlin, Germany.
    Salaneck, William R
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Electronic structure of highly ordered films of self-assembled graphitic nanocolumns2003In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 19, p. 195414-Article in journal (Refereed)
    Abstract [en]

    Highly ordered, several nanometers thick films of alkylated large planar, polycyclic aromatic hydrocarbon (PAH) molecules have been grown on semi-metallic molybdenum disulfide substrates. The films are characterized by a two-dimensional lateral arrangement of columns standing at the surface on a macroscopic scale. The self-assembly of such insulated columns of face-to-face disks with surface-induced vertical alignment has been achieved directly from solution processing. Angle-resolved photoelectron spectra revealed a highly anisotropic quasi-one-dimensional electronic structure with an extended π-electronic wave function. An intermolecular dispersion of the highest occupied band of at least 0.15 eV along the stacking direction has been measured. A partial breakdown of the concept of quasimomentum due to the finite size of the nano-objects perpendicular to the stacks is observed.

  • 158.
    Fahlman, Mats
    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.
    Smallfield, JAO
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Univ Mons, Serv Chim Mat Nouveaux, B-7000 Mons, Belgium Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA.
    Lazzaroni, R
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Univ Mons, Serv Chim Mat Nouveaux, B-7000 Mons, Belgium Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA.
    Bredas, JL
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Univ Mons, Serv Chim Mat Nouveaux, B-7000 Mons, Belgium Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA.
    Li, S
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Univ Mons, Serv Chim Mat Nouveaux, B-7000 Mons, Belgium Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA.
    Wei, Y
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Univ Mons, Serv Chim Mat Nouveaux, B-7000 Mons, Belgium Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA.
    Epstein, AJ
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, SE-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Univ Mons, Serv Chim Mat Nouveaux, B-7000 Mons, Belgium Drexel Univ, Dept Chem, Philadelphia, PA 19104 USA.
    Iron-polyaniline interfaces: Implications for corrosion protection2003In: American Chemical Society Symposium Series (ACS), ISSN 0097-6156, E-ISSN 1947-5918, Vol. 843, p. 76-89Article in journal (Refereed)
    Abstract [en]

    The early stages of interface formation between iron and a three-ring model molecule (trimer) of emeraldine base form of polyaniline (EB) were investigated using theoretical (DFT) and experimental (XPS) methods: Iron atoms were sputter-deposited in ultra high vacuum onto thin oligomer films, with X-ray photoelectron spectroscopy (XPS) core level spectra taken after each deposition. Similar studies were carried out for Fe sputter-deposited on EB polymer films as well. Based on the chemical shifts of the core level peaks and the theoretical results, iron was determined to donate charge (e(-)) into the trimer and EB films. The reverse case where thin films of trimer and EB were deposited on iron also was studied. The C(1s) core level shake up spectra show that the pi-electronic structure is modified for trimer and EB coatings on iron as compared to coatings on gold. (C) 2003 American Chemical Society.

  • 159.
    Jönsson, Stina
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, Michel P
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Groenendaal, L.
    R&D Materials, Chemistry Department, AGFA-Gevaert NV, Mortsel, Belgium.
    Salaneck, William R
    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.
    Phenyl-capped EDOT trimer: its chemical and electronic structure and its interface with aluminum2003In: Journal of Physical Chemistry B, ISSN 1520-6106, E-ISSN 1520-5207, Vol. 107, no 39, p. 10793-10800Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic properties of a phenyl-capped 3,4-(ethylenedioxy)thiophene trimer (EDOT trimer) and its interface formation with aluminum have been studied. Thin EDOT trimer films were prepared on clean gold substrates through in-situ vapor deposition. Aluminum was deposited stepwise on top of the EDOT trimer, and the initial stages of interface formation were investigated by photoelectron spectroscopy. The organic/metal interface formed was not completely abrupt; some degree of diffusion of aluminum into the EDOT trimer film occurred. The aluminum atoms preferentially react with the α-position of the trimer (C−S carbon atoms) forming covalent bonds. The formation of these covalent bonds causes a break in the π-conjugation of the system due to the introduction of sp3 defects. The charge density also is somewhat redistributed within the oligomer as a whole, mainly affecting the neighboring atoms:  sulfur and β-position of the trimer (C=C−O carbon atoms). Once the C−S carbon sites are saturated, the aluminum instead reacts with the less favorable carbon atom of the ethylene bridge (C−O−C carbons). Worth noting is the decrease in work function from 5.2 eV for sputter cleaned gold to 4.1 eV upon deposition of the EDOT trimer. Our results have several implications for organic electronics. The sp3 defects introduced by the aluminum−EDOT contacting will influence the charge injection into the material across the EDOT trimer/aluminum interface negatively. The change in work function could potentially be used to modify gold contacts for electron injection into molecules with low electron affinity.

  • 160.
    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.

  • 161.
    Jönsson, Stina
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    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.
    X-ray photoelectron spectroscopy study of the metal/polymer contacts involving aluminum and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) derivatives2003In: Journal of Materials Research, ISSN 0884-2914, E-ISSN 2044-5326, Vol. 18, no 5, p. 1219-1226Article in journal (Refereed)
    Abstract [en]

    The contact formed between aluminum and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT-PSS) derivatives was studied using x-ray photoelectron spectroscopy. The aluminum/PEDOT-PSS contact contains an interfacial layer formed by chemical reactions between aluminum and mainly poly(styrenesulfonic acid) (PSSH). These chemical interactions were studied with the help of model systems (PSSH, benzenesulfonic acid, and sodium benzenesulfonate). The preferred reaction site of aluminum is the SO3 and SO3H+ groups of the PSS chains, giving rise to C-S-Al(-O) and C-O-Al species. The resulting contact formed consists of an insulating aluminum/PSS layer and a thin region of partially dedoped PEDOT-PSS. There is significant aluminum diffusion into films of the highly conducting form of PEDOT-PSS that have substantially less PSS at the surface. Hence, no (thick) aluminum/PSS layer is formed in this case, though the PEDOT chains close to the aluminum contact will still be partially dedoped as for the aluminum/PEDOT-PSS case.

  • 162. Greczynski, G.
    et al.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Johansson, N.
    Dos, Santos D.A.
    Dos Santos, D.A., Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Dkhissi, A.
    Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Bredas, J.L.
    Brédas, J.L., Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Electronic structure of poly(9,9-dioctylfluorene) in the pristine and reduced state2002In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 116, no 4, p. 1700-1706Article in journal (Refereed)
    Abstract [en]

    The electronic structure of a polymer of interest in polymer-based light emitting devices, poly(9,9-dioctyl-fluorene), was studied using a combined experimental-theoretical approach. Results were compared with those of equivalent studies of the electronic structure of two related conjugated polymers: poly(p-phenylene) and a latter-type poly (p-phenylene) (LPPP). Finally, it was shown that electrons added to the polymer system lead to the formation of polarons at low doping levels, and bipolarons at high doping levels. The energies of the polaron and bipolaron states were measured directly, and agree with the theoretical modeling of the added electrons.

  • 163.
    Crispin, Annica
    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.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Dos, Santos D.A.
    Dos Santos, D.A., Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Cornil, J.
    Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Johansson, N.
    Bauer, J.
    Covion Organic Semiconductors GmbH, Industrial Park Hoechst, D-65926 Frankfurt, Germany.
    Weissortel, F.
    Weissörtel, F., Electrochemistry and Optoelectronic Materials, FB 6, University Duisburg, D-47048 Duisburg, Germany.
    Salbeck, J.
    Electrochemistry and Optoelectronic Materials, FB 6, University Duisburg, D-47048 Duisburg, Germany, Macromolecular Chemistry and Molecular Materials, FB 18, University Kassel, D-34132 Kassel, Germany.
    Bredas, J.L.
    Brédas, J.L., Service de Chimie des Matériaux Nouveaux, Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium, Department of Chemistry, University of Arizona, Tucson, AZ 85721-0041, United States.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Influence of dopant on the electronic structure of spiro-oligophenyl-based disordered organic semiconductors2002In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 116, no 18, p. 8159-8167Article in journal (Refereed)
    Abstract [en]

    The influence of the dopant on the electronic structure of spiro-oligophenyl-based disordered organic semiconductors was studied by means of photoelectron spectroscopy. With lithium atoms as dopants, two charges were stored on the same spiro branch in the form of bipolarons, for spiro-quarterphenyl and spiro-sexiphenyl. For doping with the sodium atoms, the size of the counter ions made it less energetically desirable to store two charges onto a single branch, and the charged species were polarons independent of the level of doping which was confirmed by optical absorption data.

  • 164. Van, Der Gon A.W.D.
    et al.
    Birgerson, J.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Modification of PEDOT-PSS by low-energy electrons2002In: Organic electronics, ISSN 1566-1199, E-ISSN 1878-5530, Vol. 3, no 3-4, p. 111-118Article in journal (Refereed)
    Abstract [en]

    The stability of conjugated organic materials under electron transport is of great importance for the lifetime of devices such as polymer light-emitting diodes (PLEDs). Here, the modification of thin films of poly(3,4- ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate) (known as PEDOT-PSS, often used in the fabrication of PLEDs) by low-energy electrons has been studied using X-ray photo-electron spectroscopy. Thin films of PSSH and molecular solid films of EDOT molecules also have been studied. We find that electrons with kinetic energies as low as 3 eV result in significant modification of the chemical structure of the materials. For thin films of PSSH, the electron bombardment leads to a strong loss of oxygen and a smaller loss of sulfur. In addition, a large amount of the sulfur atoms that remain in the films exhibits a different binding energy because of scissions of the bonds to oxygen atoms. For condensed molecular solid films of EDOT molecules, we find that the carbon atoms bonded to oxygen react and form additional bonds, as evidenced by a new component in the C(1s) peak at a higher binding energy. In the PEDOT-PSS blend, we find both effects. The importance of these observations for light-emitting diodes incorporating PEDOT-PSS films is discussed. This work demonstrates that the combination of in situ low-energy electron bombardment in combination with photo-electron spectroscopy is a powerful method to simulate and study certain processes, associated with low-energy electrons, occurring in organic based devices, which cannot be studied directly otherwise. © 2002 Elsevier Science B.V. All rights reserved.

  • 165.
    Fahlman, Mats
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Surfaces and interfaces in polymer-based electronics2002In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 500, no 1-3, p. 904-922Article in journal (Refereed)
    Abstract [en]

    Research on electronics applications such as light-emitting devices for flat-panel displays, transistors, sensors and even solid state lasers based on conducting polymers is presently under way and in some cases has reached the stage of prototype production. The mechanisms for charge injection and conduction in these materials are being studied, as are the physics of luminescence and its quenching. Lately, research into controlling film morphology through self-organizing techniques also has gained interest. Though the present interest in conducting polymers mainly concerns the pristine semiconducting state, doped conducting polymers are also studied for potential use in many applications. In this paper, we present an overview of some of the central issues in surface and interface science in the field, as well as provide our view on what may lie ahead in the future. Specifically, the importance of metal/polymer, polymer/metal and polymer/polymer interfaces is addressed. We illustrate these using polymer-based light-emitting devices, though the same type of issues appear in other polymer-based applications such as transistors and solar cells. © 2001 Elsevier Science B.V. All rights reserved.

  • 166.
    Crispin, Annica
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Jonsson, A.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Aluminum-barium interfaces on some processable poly(p-phenylene vinylene) polymers studied by photoelectron spectroscopy2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 115, no 11, p. 5252-5257Article in journal (Refereed)
    Abstract [en]

    The control of the deposition of metals on the surface of conjugated polymers determined the electronic properties of the electrical contacts. X ray photoelectron spectroscopy (XPS) and ultraviolet photon spectroscopy (UPS) was used to study the influence of an intermediate layer of barium atoms on the chemical effects that occured during the deposition of aluminium atoms of substituted poly(p-phenylvinylene) polymers. The thin films were prepared on gold substrates for spectroscopy by spin coating techniques. The diffusion of the aluminium atoms occured when the side grops were bulky and therby resulted in porous polymer films.

  • 167. 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 .
    An experimental study of poly(9,9-dioctyl-fluorene) and its interfaces with Al, LiF and CsF2001In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 175-176, p. 319-325Article in journal (Refereed)
    Abstract [en]

    Sandwich-style interfaces of Al/LiF/poly(9,9-dioctyl-fluorene) and Al/CsF/poly(9,9-dioctyl-fluorene) have been studied using X-ray and ultraviolet photoelectron spectroscopy. The polymer films were free of oxygen contamination (within the detection limits of 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 a binding energy of the core levels, nor 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 were found to dissociate at the interface but remaining in the CsF form away from the Al surface. © 2001 Elsevier Science B.V.

  • 168. 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.

  • 169. Greczynski, G.
    et al.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Hybrid interfaces of poly(9,9-dioctylfluorene) employing thin insulating layers of CsF: A photoelectron spectroscopy study2001In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 114, no 19, p. 8628-8636Article in journal (Refereed)
    Abstract [en]

    A number of sandwich-type interfaces were studied using x-ray and ultraviolet photoelectron spectroscopy including CsF/PFO/ Al/CsF/PFO, Al/CsF/Au, CsF/Al, CsF/AlxOy, and CsF/Au. The results indicate that the presence of aluminum is essential for dissociation.

  • 170. Greczynski, G.
    et al.
    Kugler, Th.
    ACREO AB, Interconnect and Packaging, Bredgatan 34, S-602 21 Norrköping, Sweden.
    Keil, M.
    Osikowicz, Wojciech
    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 .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Photoelectron spectroscopy of thin films of PEDOT-PSS conjugated polymer blend: A mini-review and some new results2001In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 121, no 1-3Article, review/survey (Refereed)
    Abstract [en]

    We present an overview of the photoelectron spectroscopy studies of thin films of the commercially important, electrically conducting polymer blend poly(3,4-ethylenedioxythiophene) oxidized with poly(4-styrenesulfonate), PEDOT-PSS. The issues discussed include the study of thermal effects, the influence of hydrochloric acid on the chemical and electronic structures of the films, phase segregation, as well as the energy level alignment at interfaces employing a PEDOT-PSS layer. All of these issues are important in applications of PEDOT-PSS as a hole-injecting electrode in polymer-based, light-emitting devices. Among the most important results are the identification of the three chemically different species in pristine PEDOT-PSS, namely poly(4-styrenesulfonic acid), poly(sodium 4-styrenesulfonate) and poly(3,4-ethylenedioxythiophene), the conversion of the sodium salt into free poly(styrenesulfonic acid) upon HCl treatment, and the decomposition of the free sulfonic acid component (presumably through loss of SO3H) induced by annealing. It is also shown that phase segregation occurs in the PEDOT-PSS system, resulting in a predominance of PSS in the surface region. This issue has been studied using different approaches, including X-ray photoelectron spectroscopy studies of the sulfur S(2p) and oxygen O(1s) core levels, ultraviolet photoelectron spectroscopy of the valence band region combined with reference measurements and quantum chemical calculations, as well as variable photon energy investigations of sulfur S(2p) core levels. It is demonstrated that, in the context of the energy level alignment at the polymer-metal interfaces, PEDOT-PSS shows metallic-like behavior. Due to the latter, the insertion of a thin PEDOT-PSS layer between the hole-injecting electrode ITO and a polymer layer of poly(bis-(2-dimethyloctylsilyl)-1,4-phenylenevinylene) leads to the lowering of the barrier for hole injection, independent of the work function of the underlying ITO. PEDOT-PSS is also used to show the alignment of the electrochemical potential across metal-polymer-metal structures. © 2001 Elsevier Science B.V. All rights reserved.

  • 171.
    Käll, Per-Olov
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry .
    Grins, J.
    Department of Inorganic Chemistry, Arrhenius Laboratory, Stockholm University, SE-10691 Stockholm, Sweden.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Söderlind, Fredrik
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    Synthesis, structure determination and X-ray photoelectron spectroscopy characterisation of a novel polymeric silver(I) nicotinic acid complex, H[Ag(py-3-CO2)2]2001In: Polyhedron, ISSN 0277-5387, E-ISSN 1873-3719, Vol. 20, no 21, p. 2747-2753Article in journal (Refereed)
    Abstract [en]

    Polymeric inorganic or organometallic coordination compounds represent an interesting class of materials where novel (combinations of) electrical, optical, magnetic, catalytic, or other properties are expected to occur. It has recently been shown that Ag1 complexes formed by organic N,N'-bidentate type ligands exhibit a rich structural variety encompassing ID, 2D and 3D polymers. Previous investigations of the silver(I) nicotinic acid system have revealed two different structural types, in both of which Ag1 is three-coordinated. We have investigated the system nicotinic acid (C6H5NO2/AgA in water (A = NO3-, CH3COO- and F-). In all the cases the same product precipitated, catena-{hydrogen bis[pyridine-3-carboxylato-(N,N')]silver(I)}, H[Ag(py-3-CO2)2] (M = 353.1 g mol-1). The structure can be described as a 1D polymer consisting of [Ag(C6H4NO2)2]- monomers linked via C21(12)[R21(4)] hydrogen bonds, where the connecting H+ ion is located at the same distance (1.24 Å) to the carboxyl oxygens of consecutive monomers. The measured X-ray photoelectron spectrum shows an excellent agreement with the proposed structure. FTIR measurements of the complex were also performed. © 2001 Elsevier Science Ltd. All rights reserved.

  • 172.
    Salaneck, William R
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Logdlund, M
    Linkoping Univ, IFM, Dept Phys, S-58183 Linkoping, Sweden Acreo AB, S-60221 Norrkoping, Sweden Linkoping Univ, ITN, Dept Nat Sci & Technol, S-60174 Norrkoping, Sweden.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Greczynski, G
    Linkoping Univ, IFM, Dept Phys, S-58183 Linkoping, Sweden Acreo AB, S-60221 Norrkoping, Sweden Linkoping Univ, ITN, Dept Nat Sci & Technol, S-60174 Norrkoping, Sweden.
    Kugler, Thomas
    Linköping University, The Institute of Technology. Linköping University, Department of Science and Technology.
    The electronic structure of polymer-metal interfaces studied by ultraviolet photoelectron spectroscopy2001In: Materials science & engineering. R, Reports, ISSN 0927-796X, E-ISSN 1879-212X, Vol. 34, no 3, p. 121-146Article, review/survey (Refereed)
    Abstract [en]

    Ultraviolet photoelectron spectroscopy has come of age. UPS can take its place beside its older, better-known sister, ESCA (or XPS) as a surface sensitive method which has become more useful in learning certain specific things about interfaces at distances significantly larger than the typical electron elastic mean-free-paths dictated by the photon energies employed, In particular, the emergence of UPS as a real tool for interfacial studies has been applications driven, evolving after needs within polymer-based electronics applications. The situation is clarified through the use of several examples, drawn from the applications-spectroscopy literature. (C) 2001 Published by Elsevier Science B.V.

  • 173.
    Greczynski, G
    et al.
    Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Electronic structure of hybrid interfaces of poly(9,9-dioctylfluorene)2000In: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 321, no 5-6, p. 379-384Article in journal (Refereed)
    Abstract [en]

    In this Letter we report the results of a study of the energy level alignment at interfaces between ultra-thin films of poly(9,9-dioctylfluorene) and AlxOy SiO2 or gold substrates, prepared under ambient (air) conditions. In all the cases, vacuum level alignment occurs, and the work function tracks that of the substrates. There is no evidence of band bending in the pristine polymer layers up to 1100 Angstrom in film thickness. Upon increasing the electrical conductivity of the polymer films by continuous doping with sodium under ultra-high-vacuum conditions, the energy levels of the polymer film gradually shift towards higher binding energies and finally become substrate independent. (C) 2000 Elsevier Science B.V. All rights reserved.

  • 174. Greczynski, G.
    et al.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Experimental study of poly(9,9-dioctyl-fluorene) and its interface with Li and LiF2000In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 166, no 1, p. 380-386Article in journal (Refereed)
    Abstract [en]

    The chemical and electronic structure of a new conjugated polymer, poly(9,9-dioctyl-fluorene) (PFO), has been studied by photoelectron spectroscopy. The polymer films were free of oxygen contamination (within the detection limits of photoelectron spectroscopy). X-ray and ultraviolet photoelectron spectroscopy was carried out on Li- and LiF-deposition on PFO as well as on LiF-deposition on aluminum. In the case of Li-deposition on PFO films, doping occurred resulting in the formation of polaronic charge carriers at low doping levels and bipolaronic charge carriers at high doping levels. LiF-deposition on PFO did not cause doping of the polymer films, nor did the LiF dissociate at the interface. No significant shifts in binding energy (BE) or work function occurred. LiF-deposition on sputter-cleaned aluminum showed evidence of surface dipole formation, though LiF dissociation was not detected. Al-deposition on LiF/PFO films did not cause dissociation of LiF, unlike the case in Alq3.

  • 175. Greczynski, G.
    et al.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Experimental study of poly(9,9-dioctyl-fluorene) and its interfaces with Li, Al, and LiF2000In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 113, no 6, p. 2407-2412Article in journal (Refereed)
    Abstract [en]

    The interaction of poly(9,9-dioctyl-fluorene) (PFO) films with Li, Al and LiF substrates was investigated by X-ray and ultraviolet photoelectron spectroscopy. The chemical and electronic structure of the interfaces were examined. The Li/PFO, LiF/PFO, LiF/Al, Al/OFO and Al/LiF/PFO interfaces were compared using Alq3.

  • 176.
    Epstein, AJ
    et al.
    Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Ohio State Univ, Dept Chem, Columbus, OH 43210 USA Linkoping Univ, Dept Sci & Technol, Linkoping, Sweden.
    Smallfield, JAO
    Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Ohio State Univ, Dept Chem, Columbus, OH 43210 USA Linkoping Univ, Dept Sci & Technol, Linkoping, Sweden.
    Guan, H
    Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Ohio State Univ, Dept Chem, Columbus, OH 43210 USA Linkoping Univ, Dept Sci & Technol, Linkoping, Sweden.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Fully sulfonated polyaniline (NSPAN) and aluminum interface: An ESCA study.2000In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 220, p. 22-POLY-Conference paper (Other academic)
  • 177.
    Fahlman, Mats
    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.
    Guan, H
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Drexel Univ, Dept Chem, Philadelphia, PA USA.
    Li, S
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Drexel Univ, Dept Chem, Philadelphia, PA USA.
    Smallfield, JAO
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Drexel Univ, Dept Chem, Philadelphia, PA USA.
    Wei, Y
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Drexel Univ, Dept Chem, Philadelphia, PA USA.
    Epstein, AJ
    Linkoping Univ, Dept Sci & Technol, SE-60174 Norrkoping, Sweden Linkoping Univ, Dept Phys, S-58183 Linkoping, Sweden Ohio State Univ, Dept Phys, Columbus, OH 43210 USA Drexel Univ, Dept Chem, Philadelphia, PA USA.
    Polyaniline-metal interfaces: Implications on corrosion protection of steel and aluminum alloys.2000In: Abstract of Papers of the American Chemical Society, ISSN 0065-7727, Vol. 220, p. 52-POLY-Conference paper (Other academic)
  • 178. Greczynski, G.
    et al.
    Fahlman, Mats
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Johansson, N.
    Thin Film Electronics Mjärdevi, Sweden.
    Dos, Santos D.A.
    Dos Santos, D.A., Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Bredas, J.L.
    Brédas, J.L., Centre de Recherche en Electronique et Photonique Moléculaires, Université de Mons-Hainaut, B-7000 Mons, Belgium.
    Polymer interfaces studied by photoelectron spectroscopy: Li on polydioctylfluorene and Alq32000In: Thin Solid Films, ISSN 0040-6090, E-ISSN 1879-2731, Vol. 363, no 1, p. 322-326Article in journal (Refereed)
    Abstract [en]

    The behavior of lithium atoms deposited on the surfaces of ultra-thin spin-coated films of poly(dioctylfluorene), and of condensed molecular solid films of tris(8-hydroxyquinoline) aluminum, have been studied through a combined experimental-theoretical approach. The Li-atoms donate charges to the organic systems, leading to doping-induced electronic states in the otherwise forbidden energy gap. The changes in the electronic structure induced by charge transfer from the Li-atoms are different in the two materials studied, and depend upon the localization of the electronic states to which the electrons are transferred. In the case of the delocalized wave functions of the p-system of poly(dioctylfluorene), at low doping levels, the added charges lead to the formation of polaron states, while at higher doping concentrations, bipolaron states are formed. In the case of the tris(8-hydroxyquinoline) aluminum, however, up to a level of three added electrons per molecule, the added electrons reside in states localized on each of the three ligands.

  • 179.
    Xing, K. Z.
    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.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Boman, Magnus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Iucci, G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bröms, P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Johansson, N.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Lögdlund, Michael
    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.
    The electronic and geometric structures of neutral and potassium-doped poly[3-(4-octylphenyl)thiophene] studied by photoelectron spectroscopy1996In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 76, no 1-3, p. 263-267Article in journal (Refereed)
    Abstract [en]

    The electronic and geometric structures of poly [3-(4-octylphenyl)thiophene] have been studied by X-ray and ultraviolet photoelectron spectroscopy (XPS and UPS, respectively). Thermochromic effects, and new charge induced states generated by potassium doping, have been observed by direct UPS measurements. The experimental results are in very good agreement with the results of theoretical quantum chemical calculations performed with the Austin Model 1 semi-empirical model and the valence-effective Hamiltonian pseudo-potential model.

  • 180.
    Xing, K. Z.
    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.
    Lögdlund, Michael
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Berggren, Magnus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Andersson, Mats R.
    Chalmers Tekniska Högskola.
    Boman, Magnus
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Stafström, Sven
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Iucci, G.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Bröms, P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Johansson, N.
    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.
    The electronic structure of neutral and alkali metal-doped poly[3-(4-octylphenyl)thiophene] studied by photoelectron spectroscopy1996In: Synthetic metals, ISSN 0379-6779, E-ISSN 1879-3290, Vol. 80, no 1, p. 59-66Article in journal (Refereed)
    Abstract [en]

    The electronic structure of poly [3-(4-octylphenyl)thiophene] (POPT) has been studied by ultraviolet photoelectron spectroscopy (UPS) and X-ray photoelectron spectroscopy (XPS), as well as by quantum chemical calculations. Both temperature-dependent effects on the electronic structure of the neutral system, as well as the generation of new electronic states induced by doping with alkaline metals, have been observed. The experimental results are in good agreement with the results of the quantum chemical calculations.

  • 181.
    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.

  • 182.
    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.

  • 183.
    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.

  • 184.
    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.

  • 185.
    Li, Guowei
    et al.
    Max Planck Inst Chem Phys Solids, Germany.
    Fu, Chenguang
    Max Planck Inst Chem Phys Solids, Germany.
    Shi, Wujun
    ShanghaiTech Univ, Peoples R China.
    Jiao, Lin
    Max Planck Inst Chem Phys Solids, Germany.
    Wu, Jiquan
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Yang, Qun
    Max Planck Inst Chem Phys Solids, Germany.
    Saha, Rana
    Max Planck Inst Microstruct Phys, Germany.
    Kamminga, Machteld E.
    Univ Groningen, Netherlands.
    Srivastava, Abhay K.
    Max Planck Inst Microstruct Phys, Germany.
    Liu, Enke
    Max Planck Inst Chem Phys Solids, Germany.
    Yazdani, Aliza N.
    Carleton Coll, MN 55057 USA.
    Kumar, Nitesh
    Max Planck Inst Chem Phys Solids, Germany.
    Zhang, Jian
    Tech Univ Dresden, Germany.
    Blake, Graeme R.
    Univ Groningen, Netherlands.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Wirth, Steffen
    Max Planck Inst Chem Phys Solids, Germany.
    Auffermann, Gudrun
    Max Planck Inst Chem Phys Solids, Germany.
    Gooth, Johannes
    Max Planck Inst Chem Phys Solids, Germany.
    Parkin, Stuart
    Max Planck Inst Microstruct Phys, Germany.
    Madhavan, Vidya
    Univ Illinois, IL 61801 USA; Univ Illinois, IL 61801 USA.
    Feng, Xinliang
    Tech Univ Dresden, Germany.
    Sun, Yan
    Max Planck Inst Chem Phys Solids, Germany.
    Felser, Claudia
    Max Planck Inst Chem Phys Solids, Germany.
    Dirac Nodal Arc Semimetal PtSn4: An Ideal Platform for Understanding Surface Properties and Catalysis for Hydrogen EvolutionIn: Angewandte Chemie International Edition, ISSN 1433-7851, E-ISSN 1521-3773Article in journal (Refereed)
    Abstract [en]

    Conductivity, carrier mobility, and a suitable Gibbs free energy are important criteria that determine the performance of catalysts for a hydrogen evolution reaction (HER). However, it is a challenge to combine these factors into a single compound. Herein, we discover a superior electrocatalyst for a HER in the recently identified Dirac nodal arc semimetal PtSn4. The determined turnover frequency (TOF) for each active site of PtSn4 is 1.54 H-2 s(-1) at 100 mV. This sets a benchmark for HER catalysis on Pt-based noble metals and earth-abundant metal catalysts. We make use of the robust surface states of PtSn4 as their electrons can be transferred to the adsorbed hydrogen atoms in the catalytic process more efficiently. In addition, PtSn4 displays excellent chemical and electrochemical stabilities after long-term exposure in air and long-time HER stability tests.

  • 186.
    Jönsson, Stina
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Södergren, H.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Perzon, E.
    Department of Material and Surface Chemistry, Chalmers University of Technology, Gothenburg, Sweden.
    Chen, Miaoxiang
    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.
    Andersson, M. R.
    Department of Material and Surface Chemistry, Chalmers University of Technology, Gothenburg, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    de Jong, M. P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Tengstedt, Carl
    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.
    Electronic structure of novel low band gap conjugated polymersManuscript (preprint) (Other academic)
    Abstract [en]

    The electronic structures of two novel low band gap conjugated polymers have been studied. Both materials are conjugated alternating copolymers based on fluorene units and low band gap donor-acceptor-donor units. The emphasis in this study has been to study the valence and the conduction bands. In particular the degree of localization or delocalization along the polymers and the symmetry of these states have been studied, since these features can be related to their transport properties. The main experimental part of this work is photoelectron spectroscopy, near-edge X-ray photon absorption and resonant photoemission. These techniques have been used to probe the frontier electronic structure of these systems. The experimental results are interpreted with the help of density functional theory calculations. The valence bands are dispersed originating from orbitals delocalized along the polymer chain shile the conduction bands are more flat, as they are derived from orbitals localized on the acceptor units. This band structure would predict good hole transporting properties but poor electron transport.

  • 187.
    Lindell, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Salaneck, William R.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Energy level alignment at metal-organic and organic-organic interfaces with Alq3 and NTCDAManuscript (preprint) (Other academic)
    Abstract [en]

    The energy level alignment behavior of the widely used materials tris-(8-hydroxyquinoline)aluminum (Alq3) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA) is investigated. The Integer Charge Transfer (ICT) model is successfully used to predict their overall behavior at weakly-interacting hybridorganic and organic-organic interfaces, including NTCDA/Alq3 bilayers. The EICT- of NTCDA is measured to be 4.35 eV and the EICT+ of Alq3 is found to be 4.3 eV. The Alq3 films furthermore feature an interface dipole in absence of charge transfer due to the intrinsic dipole of the molecule and ordering effects.

  • 188.
    Tengstedt, Carl
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Braun, Slawomir
    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.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Poly(3.4-ethylene dioxythiophene)- and polyaniliane-Poly(perfluoroethylenesulfonic acid) as hole injecting layers in polymer light emitting devicesManuscript (preprint) (Other academic)
    Abstract [en]

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

  • 189.
    Bhatt, Pramod
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Rao, K. V.
    Division of Engineering Material Physics, Royal Institute of Technology, Stockholm, Sweden.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Room temperature magnetism in thin film nickel-tetracynoethyleneManuscript (Other academic)
    Abstract [en]

    Room temperature magnetic ordering is reported in Ni-Tetracynoethelene (TCNE) thin films fabricated on gold substrates using physical vapor deposition (PVD) under ultra high vacuum conditions. This technique enables preparation of very clean films without having any kind of contamination from oxygen-containing species, solvents or precursor molecules. Film thickness and stoichiometry were obtained from x-ray photoelectron spectroscopy (XPS) measurements. XPS derived stoichiometry points to a 1:2 ratio between Ni and TCNE resulting in Ni(TCNE)x, x ~ 2. No evidence of pure Ni metal in the in situ grown films were present in the XPS and UPS measurements within the detection limits of the techniques.

  • 190.
    Lindell, Linda
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Vahlberg, Cecilia
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Sensor Science and Molecular Physics . Linköping University, The Institute of Technology.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry . Linköping University, The Institute of Technology.
    Self assembled monolayer engineered interfaces for determination of charge transfer and charge separated statesManuscript (preprint) (Other academic)
    Abstract [en]

    Most interfaces in organic electronics consists of weakly interacting organic/(in)organic material interfaces where the interaction is limited to charge transfer via tunnelling. In order to optimize device structure and performance, it is of great importance to understand the rules that govern the energy level alignment at those interfaces. The integer charge transfer (ICT) model is a model used to explain and predict the interaction and energy level alignment behaviour from the so-called integer charge transfer energy, EICT values. In this paper we investigate two phenomena that could influence the absolute value of EICT at hybrid organic and organic-organic interfaces and provide experimentally-derived quantitative data on the strength of the effects.

  • 191.
    Bao, Qinye
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fabiano, Simone
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Andersson, Mattias
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Braun, Slawomir
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Sun, Zhengyi
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Liu, Xianjie
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    Fahlman, Mats
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering.
    The energetics of the semiconducting polymer-electrode interface for solution-processed electronicsManuscript (preprint) (Other academic)
    Abstract [en]

    The semiconductor-electrode interface impacts the function and the performance of (opto-)electronic devices. For printed organic electronics the electrode surface is not atomically clean leading to weakly interacting interfaces. As a result, solution-processed organic ultra-thin films on electrodes typically form islands due to de-wetting. It has therefore been utterly difficult to achieve homogenous ultrathin conjugated polymer films. This has made the investigation of the correct energetics of the conjugated polymer-electrode interface impossible. Also, this has hampered the development of devices including ultra-thin conjugated polymer layers. Here, we report Langmuir-Shäfer-manufactured homogenous mono- and multilayers of semiconducting polymers on metal electrodes and track the energy level bending using photoelectron spectroscopy. The amorphous films display an abrupt energy level bending that does not extend beyond the first monolayer. Our findings provide new insights of the energetics of the polymer-electrode interface and opens up for new high-performing devices based on ultra-thin semiconducting polymers.

  • 192.
    Jakobsson, Fredrik L. E.
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Marsal, Philippe
    Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Braun, Slawomir
    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.
    Cornil, Jérôme
    Laboratory for Chemistry of Novel Materials, University of Mons-Hainaut, Place du Parc 20, B-7000 Mons, Belgium.
    Fahlman, Mats
    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.
    Tuning the energy levels of photochromic diarylethene compounds for optoelectronic switch devicesManuscript (Other academic)
    Abstract [en]

    Photochromic diarylethene molecules (PC) is investigated for use in opticalwrite/electrical read memory applications. The frontier energy levels and dipolemoment is calculated using density functional theory. Good agreement is foundbetween calculated electronic structure and measured ultraviolet photoelectronspectra. The changes in frontier energy levels and dipole moment are scrutinizedupon two different approaches for chemical modification: (i) adding substituentsto the ethylene bridge; or (ii) changing the chemical nature of the aryl rings.Through the chemical modification the frontier energy levels can be tuned bymore than 2 eV. The calculated molecular properties are used in charge transportmodels to predict the behavior of devices based on these molecules. By using thePC in combination with an organic semiconductor (in bilayer or blend) goodswitching behavior can be achieved in a device. The switch effect is predicted tobe mainly due to switch in frontier energy levels rather than switch of dipolemoment. This is concluded since the dipole moment is either too small (< 5 D) orthe switch effect to small (less than a factor of two).

  • 193.
    Tengstedt, Carl
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, M. P.
    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.
    Fahlman, Mats
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    UV-ozone treatment of PEDOT-based materials resulting in increased work functionsManuscript (preprint) (Other academic)
    Abstract [en]

    We describe a simple method to increase the work function of PEDOT-PFESA and PEDOT-PSS by short exposure to UV and ozone in a "UVO-Cleaner®". The creation of carbonyl gmups in the surface region fotms a dipole layer shifting the vacuum level with a followed increase in work function. It has been shown that the work function of PEDOT-PFESA can be increased by as much as -0.4 eV to the absolute value of 6.3 eV and by at least -0.2 eV for PEDOT-PSS to the absolute value of 5.4 e V. The increase in work function has also proven to be time dependent with the largest increasing rate occuning for short exposure times. Upon ozone treatment, both PEDOT and PSS are oxidized whereas PFESA seems to be unaffected.

  • 194.
    Tengstedt, Carl
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    de Jong, M. P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    Kanciurzewska, Anna
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Carlegrim, Elin
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Salaneck, William R.
    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.
    V(TCNE)x: the electronic structure of an enigmatic, organic-based room temperature magnet revealedManuscript (preprint) (Other academic)
    Abstract [en]

    We have prepared and characterized thin films of V(TCNE)x in ultra-high vacuum using a novel film growth technique based on in-situ chemical vapor deposition of tetracyanoethylene, TCNE, and bis-benzene vanadium, V(C6H6)2. The in-situ preparation method enabled, for the first time, experimental analysis of the electronic structure. X-ray magnetic circular dichroism (XMCD) measurements recorded at the V L2,3-edge confirmed room temperature magnetic ordering. A combination of conventional photoelectron spectroscopy (PES) and resonant photoemission (RPE) measured at the x-ray absorption edges (V L3-edge, C K-edge, N K-edge) shows that the highest occupied electronic state is V(3d)-derived. Nearly complete quenching of the V(3d) orbital angular momentum is observed from the low value of the integrated XMCD signal, indicating a strong ligand field. The rearrangements of the TCNE" related valance electronic states observed in PED and near edge x-ray absorption fine structure (NEXAFS) spectra, in combination with the evidence of V(3d) and TCNE" π (π*) orbital overlap contained in RPE spectra, also point to strong, covalent type bonding.

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