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1.	Ruseckas, A., et al. (författare) Luminescence from inter-chain aggregates in polythiophene films 2001 Ingår i: Synthetic Metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 603-604 Tidskriftsartikel (refereegranskat)abstract We report time-resolved photoluminescence of two polythiophene derivatives with different chain packing. Emission of inter-chain aggregates is distinguished from that of intra-chain singlet excitons. The aggregate luminescence is shifted towards lower energies relative to that of intra-chain exciton by 0.17 eV, and the Huang-Rhys factor of the coupling to the intra-chain C double bondC vibration is S = 1.5. The excitonic coupling in aggregates is of intermediate strength.
2.	Theander, M., et al. (författare) Interchain photoluminescence in substituted polyfluorenes 2001 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 615-616 Tidskriftsartikel (refereegranskat)abstract We have characterised the interchain emitting states of two substituted polyfluorenes with steady-state and time-resolved photoluminescence (PL). Site selective excitation of the interchain state shows that physical dimers are formed in the film. These dimers have low concentration in the films but exciton diffusion to the dimers is reducing the intrachain exciton lifetime. With asymmetrical substituents, the PL quantum yield is higher and the PL lifetime is longer due to lower concentration of dimers. Slow cooling from the melt, gives a new red shifted emission band and less intrachain emission. A discrepancy in the calculated radiative lifetimes suggest a fast formation of this new band.
3.	Jager, Edwin, 1973-, et al. (författare) Polypyrrole micro actuators 1999 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 102:1-3, s. 1309-1310 Tidskriftsartikel (refereegranskat)abstract The doping and undoping of conjugated polymers is accompanied by a volume change. This volume change can be used to make micro-actuators. We have built polypyrrole (PPy) gold bilayer structures. The volume change of PPy induces a bending of the bilayer. We have made micro-actuators based on this principle, which have been examined with video-microscopy. Some applications for these microactuators are proposed, including opening and closing boxes for cell biology and nanoliter chemistry and micro-robotics.
4.	Aasmundtveit, K.E., et al. (författare) Structural aspects of electrochemical doping and dedoping of poly(3,4-ethylenedioxythiophene) 2000 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 113:1, s. 93-97 Tidskriftsartikel (refereegranskat)abstract Electrochemical dedoping and redoping of p-toluene sulfonate doped poly(3,4-ethylenedioxythiophene) (PEDOT) has been studied with in situ grazing incidence diffraction with water used as an electrolyte. The diffraction peak positions and integrated intensities do not change significantly during doping and dedoping, while the peak widths increase upon dedoping and decrease upon doping. This implies that the lattice parameters and the relative positions of the polymer chains and the p-toluene sulfonate ions remain unchanged, the redox processes being carried out by the motion of smaller ions between the polymer and the electrolyte, and that the structural order decreases upon dedoping and increases upon doping in a reversible manner.
5.	Andersson, Mats R., et al. (författare) Improved photoluminescence efficiency of films from conjugated polymers 1997 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 85:1-3, s. 1383-1384 Tidskriftsartikel (refereegranskat)abstract We have demonstrated two general ways to increase the photoluminescence efficiency of films from conjugated polymers. One is to disperse the conjugated polymer on a molecular level by using attractive forces between the conjugated polymer and the matrix. The other method is to substitute the conjugated polymer with side chains which separates the conjugated backbones. Using this idea a new poly(thiophene) with a photoluminescence efficiency of 16% in films has been prepared. LEDs from this polymer exhibit an external efficiency of 0.1% for single layer and 0.7% for double layer diodes.
6.	Andersson, Mats R., et al. (författare) Synthesis of poly(alkylthiophenes) for light-emitting diodes 1995 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2183-2184 Tidskriftsartikel (refereegranskat)abstract We have demonstrated a general way to tune the emission of poly(alkylthiophenes) by using steric interaction between the repeating units. Light-emitting diodes prepared of the polymers have blue to near-infrared emission.
7.	Andersson, M.R., et al. (författare) The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV 2001 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 63-64 Tidskriftsartikel (refereegranskat)abstract We present the synthesis and characterisation of poly(2-(2',5'-bis(2?-ethylhexyloxy)phenyl)-1, 4-phenylenevinylene) (BEHP-PPV) polymerised under different conditions. The photoluminescence efficiencies (?PL) in the solid state of BEHP-PPV obtained at 144°C and 0°C are 28% and 60%, respectively. Polymerisation temperatures below 0°C decreases the molecular weight without changing the photoluminescence efficiency to any large extent.
8.	Bantikassegn, W., et al. (författare) Proceedings of the International Conference on Science and Technology of Synthetic Metals Electronic properties of polypyrrole (polystyrene-sulphonate)/metal junctions 1993 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 55:1, s. 36-42 Tidskriftsartikel (refereegranskat)abstract The nature of polymer/metal interfaces is decisive for the operation of polymer based electronic devices. At such interfaces charge transport may be affected by barrier formation, or by formation of insulating interfaces of various types. We have prepared thin films of conducting polypyrrole doped with large polymeric anions of polystyrenesulphonate for studies in metal/polymer junctions. Aluminium and gold contacts are vacuum deposited to form metal/polymer/gold sandwich structures. The current-voltage characteristics show that the interface between polypyrrole and gold is ohmic with no current limitation. However, the aluminium/polypyrrole interface forms highly resistive and nonohmic contacts. Photoelectron spectroscopy using UV and X-ray photons reveals a decrease of the work function upon Al deposition, reactions between Al and the sulphonate anions, and immediate oxidation of the aluminium upon exposure to oxygen. These observations corroborate the interpretation that the current limitation found at Al/polypyrrole junctions is due to formation of insulating aluminium oxide, not excluding reactions between the metal and dopant. It is also pointed out that interfaces between reactive metals and polymers are prone to such oxide interface formation, considering the high diffusivity of oxygen in many polymers.
9.	Berggren, Magnus, et al. (författare) Controlling colour by voltage in polymer light emitting diodes 1995 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 71:1-3, s. 2185-2186 Tidskriftsartikel (refereegranskat)abstract We report electroluminescence using different substituted polythiophenes as the emitting mterial. Different substituents cause different sterical interacion which force the thiophene rings out of planarity. This results in different bandgaps. Colours from blue to near infrared have been demonstrated in electroluminescent devices. We also demonstrate voltage controlled electroluminescence using mixtures of these polymers.
10.	Berggren, Magnus, et al. (författare) Organic lasers based on Forster transfer 1997 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 91:1-3, s. 65-68 Tidskriftsartikel (refereegranskat)abstract The light amplification characteristics of organic guest-host systems with Forster transfer from absorbing small molecule hosts to dye/ polymer dopants are described. Such material systems are shown to be very promising for use in low-threshold organic lasers. A number of laser resonators have been experimentally realized with Forster gain media including microdisk, ring, spheroid, and distributed Bragg reflector lasers. (C) 1997 Elsevier Science S.A.
11.	Berggren, Magnus, et al. (författare) Polymer light-emitting diodes placed in microcavities 1996 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 76:1-3, s. 121-123 Tidskriftsartikel (refereegranskat)abstract The use of resonant optical microcavities to influence the emission properties of conjugated polymer light-emitting diodes (LEDs) is reported. The microcavities, which are built using metallic mirrors and polymeric spacers, incorporate polymer LEDs in between the mirrors. We report experimental results of polymer LEDs based on substituted polythiophenes. The effects include substantial narrowing of the spectral width of the emitted light, enhancement of the emission at the microcavity resonance, and coupling of two emission processes to different resonance modes in the same cavity.
12.	Birgerson, J., et al. (författare) Doped polymeric cathodes for PPV/Al based LEDs 2002 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 132:1, s. 57-61 Tidskriftsartikel (refereegranskat)abstract The effect of Li-doping in poly(para-phenylenevinylene) (PPV) based light emitting devices has been studied. In a standard structure with an indium tin oxide (ITO) anode, poly(3,4-ethylenedioxythiophene) doped with poly(4-styrenesulfonate) (PEDOT-PSS)-layer and an active PPV-layer, the effects of a thin (around 1 Å) Li-layer and a thin layer, (50 Å), of a large bandgap polymer, poly(2,5-diheptyl-1,4-phenylene-alt-1,4-naphthylene) (P14NHP) between the PPV and the aluminum cathode have been studied in terms of IV-characteristics and efficiency. The Li-atoms dope the interfacial layer of the PPV as seen by photoelectron spectroscopy. A thin layer of Li improves the charge balance by decreasing the energy barrier for injection of electrons for the Al/Li/PPV/PEDOT-PSS/ITO device. The efficient electron injection originates from a Fermi level alignment between the doped polymer and the aluminum cathode, which reduces the energy barrier. A thin layer of the large bandgap polymer P14NHP, between the PPV and Al contact, increases the light output and efficiency by blocking the holes. In addition, it may also reduce the light quenching by moving the region of recombination away from the Al-contact. The addition of a Li-layer on top of P14NHP leads to an increase of the quantum efficiency, because of better electron injection. © 2002 Elsevier Science B.V. All rights reserved.
13.	Birgerson, J., et al. (författare) Electronic structure of some conjugated polymers for electron transport 2001 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 122:1, s. 67-72 Tidskriftsartikel (refereegranskat)abstract The chemical and electronic structure of three different, strictly alternating copolymers, poly(2,5-diheptyl-1,4-phenylene-alt-1,4-naphthylene) (P14NHP), poly(2,5-diheptyl-1,4-phenylene-alt-2,6-naphthylene) (P26NHP) and poly(2,5-diheptyl-1,4-phenylene-alt-9,10-anthrylene) (P910AHP), have been studied by photoelectron spectroscopy and optical absorption spectroscopy. The experimental results have been analyzed using the results of quantum chemical calculations. In the geometrical structure of all three of the polymers there are large torsion angles between the phenylene unit and the naphthylene or anthrylene units. These large torsion angles lead to localization of the p-electron wave functions, and minimal conjugation along the polymer backbone. For all three polymers, the highest occupied molecular orbital is completely localized to the naphthylene or anthrylene unit. The frontier molecular orbital wave functions are very reminiscent of the highest occupied orbitals of the isolated naphthalene or anthracene molecules. The optical absorption spectra of all three polymers verify the existence of large optical band gaps, consistent with the large torsion angels. The first several optical transitions in the polymers are also very reminiscent of the transitions in single naphthalene and anthracene molecules.
14.	Bolognesi, A., et al. (författare) High photoluminescence efficiency in substituted polythiophene aggregates 2003 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 139:2, s. 303-310 Tidskriftsartikel (refereegranskat)abstract In this paper we discuss the optical (absorption and photoluminescence) and solvatochromic properties of a newly synthesized alternating copolymer based on poly(3-alkylthiophene) structure. In this copolymer an unsubstituted thiophene ring is linked to a 3-alkyl-substituted thiophene, the two repeating units being alternated in the copolymer chains. Moreover, a bulky group, THP, with high steric hindrance has been introduced in the side chain. This copolymer, designed to preserve the backbone planarity of polythiophenes and to prevent a close packing arrangement through the non-regioregular insertion of the bulky substituted monomer, shows high PL quantum yield in the solid state and in solution aggregates. The electroluminescence of this copolymer is reported for a simple single layer device. © 2003 Elsevier Science B.V. All rights reserved.
15.	Bröms, P., et al. (författare) Optical absorption studies of sodium doped poly(cyanoterephthalylidene) 1994 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 67:1-3, s. 93-96 Tidskriftsartikel (refereegranskat)abstract The effects of doping poly(cyanoterephthalylidene) with sodium in ultrahighvacuum been studied by optical absorption spectroscopy. Upon doping, new optical transitions are observed within the bandgap; the characteristics of these transitions are consistent with the formation of bipolarons. The optical absorption results are confirmed by direct measurements of the doping-induced gap states using ultraviolet photoelectron spectroscopy.
16.	Dannetun, Per, et al. (författare) Interface formation between poly(2,5-diheptyl-p-phenylenevinylene) and calcium : implications for light-emitting diodes 1994 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 67:1-3, s. 133-136 Tidskriftsartikel (refereegranskat)abstract 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.
17.	Dannetun, Per, et al. (författare) 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 molecules 1993 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 55:1, s. 212-217 Tidskriftsartikel (refereegranskat)abstract The interaction between aluminum and Î±-Ï‰-diphenyltetradecaheptaenee (DP7), Î±-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 Ï€-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 Î±-carbons of the thiophene nits of 6T.
18.	Dannetun, P., et al. (författare) The eletronic structure of emeraldine doped in situ from HCl in the gas phase as studied by photoelectron spectroscopy 1991 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 41:1-2, s. 645-648 Tidskriftsartikel (refereegranskat)abstract The chemical and electronic structure of spin-coated films of polyaniline in the emeraldine state, treated in-situ with HCl in the gas phase, have been studied for the first time by means of X-ray Photoelectron Spectroscopy (XPS) and Ultra-violet Photoelectron Spectroscopy (UPS). Ultra thin films, of about several hundreds of Ã…ngstrÃ¶ms thickness, were spin-coated from a solution of chemically prepared emeraldine in NMP, onto substrates of aluminum or silicon. The salt forms were prepared both by (a) â€œwetâ€ doping in 1M HCl and (b) the in-situ treatment of the films with HCl in the gas phase. With XPS three different types of chlorine have been observed, two ionic and one covalent. With UPS the valence band spectra of the doped and undoped state, are studied.
19.	Dannetun, Per, et al. (författare) The evolution of charge-induced gap states in degenerate and non-degenerate conjugated molecules and polymers as studied by photoelectron spectroscopy 1994 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 67:1, s. 81-86 Tidskriftsartikel (refereegranskat)abstract 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.
20.	Ding, L., et al. (författare) Photovoltaic cells with a conjugated polyelectrolyte 2000 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 110:2, s. 133-140 Tidskriftsartikel (refereegranskat)abstract We describe photovoltaic cells made from a novel conjugated polyelectrolyte, the lithium salt of poly(thiophene-3-acetic acid) (PTAA-Li). The aqueous solubility of this polyelectrolyte allows formation of blend electrodes with a dispersion of the metallic polymer Poly(Ethylene DiOxyThiophene) (PEDOT). The incident monochromatic photon to current conversion efficiency (IPCE) of the cells were improved up to 19% by blending PTAA-Li with PEDOT to modify the ITO electrode, in combination with the low bandgap polymer poly(3-(4-octylphenyl)thiophene) (POPT), and C60 as electron acceptor. We attribute the increase of efficiency to the improved contact area between the conjugated polyelectrolyte and PEDOT.
21.	Edman, Ludvig, 1967-, et al. (författare) Influence of the anion on the kinetics and stability of a light-emitting electrochemical cell 2003 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 138:3, s. 441-446 Tidskriftsartikel (refereegranskat)abstract The selection of the anion is shown to be crucial for the response time and the lifetime of light-emitting electrochemical cells (LECs) fabricated with [co-block phenyl-substituted poly(para phenylene vinylene)]-PEO-LiX (X = Tf, TFSI, Tf-TFSI). With a mixed-anion (X = Tf-TFSI) salt. the LEC turned on in less than 0.4 s at ΔU = 4.0 V, with X = TFS1 it turned on in a few seconds, while X = Tf produced devices with significantly larger response times with a strong dependence on the film thickness. We attribute this significant variation in the response to the morphology of the PEO-LiX phase at room temperature: PEO-LiTf is largely crystalline with a correspondingly limited ionic mobility: PEO-LiTf-TFSI is amorphous with a relatively high mobility; and heat-treated PEO-LiTFSI is typically partially amorphous. For lifetimes. we focused on 3.0 ≤ ΔU ≤ 4.0 V since this range coincided with a crossover in performance for the X = Tf devices. At ΔU = 3.0 V, these lasted the entire measurement cycle (=55 h) with constant efficiency and only a small decrease in light output. At ΔU ≥ 3.25 V. the same devices exhibited a limited lifetime with a linear dependence on the salt concentration and a decrease in the efficiency with time. For X = TFSI. Tf-TFSI short lifetimes and a decrease in efficiency with time were obtained independent of the applied voltage. Considering recently published data on electrochemical stability, we propose that an irreversible overreduction of the anion is a significant side reaction that limits the lifetime of LEC systems.
22.	Fredriksson, C., et al. (författare) Theoretical studies of the aluminum/poly(p-phenylene vinylene) interface 1993 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 57:2, s. 4632-4637 Tidskriftsartikel (refereegranskat)abstract A molecular quantum chemical approach is used to study the aluminum on PPV (Poly(p-Phenylene Vinylene)) interface. We focus on modifications to the chemical and electronic structure of the polymer upon interaction with a submonolayer of aluminum. A model system, trans-stilbene, is taken to investigate the nature of the Al-PPV bonding. Energetically favorable conformations are then used as prototypes to study the evolution of the electronic structure as modified by the reaction with aluminum. Results at the ab initio Hartree-Fock level indicates that Al atoms react with the vinylene linkage rather than the phenyl groups at early stages of interface formation.
23.	Fredriksson, C., et al. (författare) Theoretical studies of the aluminum/trans-polyacetylene interface : Calculations of model systems and comparison to experiment 1993 Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 57:2-3, s. 4590-4595 Tidskriftsartikel (refereegranskat)abstract The interaction between Al atoms and trans-polyacetylene has been studied quantum chemically at the ab initio Hartree-Fock level using oligomeric model systems. Investigations of the Al-polyacetylene bonding and modifications to the chemical and electronic structure of model systems for polyacetylene upon interaction with Al atoms are reported. The density-of-states is calculated for a polyene chain interacting with a pair of Al atoms. The results are discussed in relation to photoelectron spectra taken during Al deposition on an oligomeric model for polyacetylene (a diphenylpolyene with 7 C=C bonds in the polyene segment).
24.	Ghosh, S., et al. (författare) Nano-structured conducting polymer network based on PEDOT-PSS 2001 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 121:1-3, s. 1321-1322 Tidskriftsartikel (refereegranskat)abstract Poly(3,4-ethylenedioxythiophene)-polystyrenesulphonate (PEDOT-PSS) has been crosslinked into network morphology. The morphologies of different crosslinked PEDOT-PSS firms have been characterised by atomic force microscopy (AFM). The crosslinked polymer shows highly efficient and fast redox activity, both in aqueous and non-aqueous media.
25.	Gigli, G., et al. (författare) A novel electroluminescent oligothiophene 2001 Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 581-582 Tidskriftsartikel (refereegranskat)abstract We report investigations of the photoluminescence (PL) and electroluminescence (EL) of a novel substituted thiophene oligomer. The high PL efficiency in solid state (23%), the high electron affinity, together with the good processability make this material competitive for applications in organic emitting diodes (LEDs). EL efficiency of 0.1% is demonstrated in a stable LED with spin coated active layer.

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