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

  • Resultat 11-20 av 29
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11.
  • Johansson, Tomas, et al. (författare)
  • Electrochemical bandgaps of substituted polythiophenes
  • 2003
  • Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 13:6, s. 1316-1323
  • Tidskriftsartikel (refereegranskat)abstract
    • The electrochemical bandgaps for different soluble substituted polythiophenes have been measured by cyclic voltammetry. The effect of substituents on the oxidation/reduction potentials is discussed. Bandgaps obtained by cyclic voltammetry have been found to be in general higher than optical bandgaps. Among regioregular polymers substituted with a phenyl group at position 3 of the thiophene ring, examples are found that give very symmetric voltammograms. Rationalization for this behaviour is discussed from a conformational point of view.
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12.
  • Jonforsen, M., et al. (författare)
  • Photodiodes made from poly(pyridopyrazine vinylene) : polythiophene blends
  • 2001
  • Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 185-186
  • Tidskriftsartikel (refereegranskat)abstract
    • A PPV-type polymer with the pyridopyrazine heterocycle (EHH-PPyPzV) has been synthesised and found to have high electron affinity according to electrochemical measurements. When used as the electron accepting material in single-layer-photodiodes, with a thiophene copolymer (PEOPT-co-PAAPT) as the electron donating material, IPCE (incident photon to current conversion efficiency) up to 1% was measured. Atomic force microscopy was used to analyse the blend morphology in the devices.
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13.
  • Jonforsen, M., et al. (författare)
  • Synthesis and characterization of poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with phenyl substituted side-groups
  • 2002
  • Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 131:1-3, s. 53-59
  • Tidskriftsartikel (refereegranskat)abstract
    • Poly(quinoxaline vinylene) and poly(pyridopyrazine vinylene) with 3(2'-ethylhexyloxy)phenyl side-groups have been synthesized and compared with similar polymers with purely aliphatic side-chains. The new polymers had smaller bandgaps, and from cyclic voltammetry it was seen that the phenyl substituted side-groups made the polymers easier to reduce, with half wave potentials of -1.02 and -1.33 V versus Ag/AgCl for the poly(pyridopyrazine vinylene) and poly(quinoxaline vinylene) respectively. The attachment of the phenyl substituted side-groups had counteracting effects on the stability towards photo-oxidation, which resulted in improved stability of the poly(pyridopyrazine vinylene) compared to its equivalent with purely aliphatic side-chains, while the poly(quinoxaline vinylene) showed decreased stability. © 2002 Elsevier Science B.V. All rights reserved.
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14.
  • Kaminorz, Y., et al. (författare)
  • Characteristics of polythiophene surface light emitting diodes
  • 2000
  • Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 113:1, s. 103-114
  • Tidskriftsartikel (refereegranskat)abstract
    • Surface light emitting diodes (SLEDs), in which previously microfabricated electrodes were coated with a conjugated polymer, were made with greatly different electrode spacings (250 nm and 10 or 20 µm) and with different electrode material combinations. The fabrication process allowed us to compare several electrode materials. The SLED structures also enabled imaging of the light emission zone with fluorescence video microscopy. Conventional sandwich structures were also made for comparison (electrode separation 50 nm). In this study, the emitting layer was poly[3-(2',5'-bis(1?,4?,7?trioxaoctyl)phenyl)- 2,2'-bithiophene] (EO-PT), a conjugated polymer based on polythiophene with oligo(ethyleneoxide) side chains. The current-voltage (I(V)) and light-voltage (L(V)) characteristics of the SLEDs were largely insensitive to electrode separation except at high voltages, at which the current in the devices with the largest separations was limited. Sandwich structures had the same light output at a given current. Light could be obtained in forward and reverse bias from indium tin oxide (ITO)-aluminum, gold silicide-aluminum, and gold silicide-gold SLEDs, but the turn-on voltages were lowest with the ITO-aluminum devices, and these were also the brightest and most reliable. Adding salt to the EO-PT increased the current and brightness, decreased the turn-on voltages, and made the I(V) characteristics symmetric, thus, a device with an electrode separation of 10 µm had the extraordinarily low turn-on voltage of 6 V. The location of the light emission was at the electron-injecting contact.
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15.
  • Mammo, W., et al. (författare)
  • New low band gap alternating polyfluorene copolymer-based photovoltaic cells
  • 2007
  • Ingår i: Solar Energy Materials and Solar Cells. - : Elsevier BV. - 0927-0248 .- 1879-3398. ; 91:11, s. 1010-1018
  • Tidskriftsartikel (refereegranskat)abstract
    • New low band gap alternating polyfluorene copolymers were synthesized for use in plastic solar cells and their optical, electrochemical, and photovoltaic characteristics were determined. These polymers incorporated fluorene units alternating with groups including electron-withdrawing (A) and electron-donating (D) groups in donor-acceptor-donor (DAD) sequence to achieve the lowering of band gaps. The HOMO-LUMO values were estimated from electrochemical studies. By varying the donor and acceptor strength and position of the solubilizing substituents, similar HOMO values were obtained. These values were also found to correlate well with the open circuit voltage (VOC) values determined from photovoltaic data of the polymers blended with the acceptor PCBM. Despite similar HOMO values, the absorption spectra of the polymers differ significantly. This prompted the preparation of photovoltaic devices consisting of blends of two polymers with complementary absorptions in combination with PCBM to harvest more photons in the polymer solar cells. © 2007 Elsevier B.V. All rights reserved.
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16.
  • Nilsson, K.Peter R., et al. (författare)
  • Conformational transitions in a free amino acid functionalized polythiophene
  • 2003
  • Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 135-136, s. 291-292
  • Tidskriftsartikel (refereegranskat)abstract
    • A chiral, 3-substituted polythiophene with an amino acid function shows pH-dependent visible, emission and circular dichroism spectra in buffered aqueous solution. At pH equal to pi of the amino acid, the backbone adopts a non-planar right-handed helical conformation and the polymer chains are separated from each other. Increasing pH leads to a more planar conformation of the backbone and an aggregation of the polymer chains occurs. A lower pH will also lead to a more planar conformation of the backbone, but aggregation of the polymer chains appears to be absent. © 2003 Elsevier Science B.V. All rights reserved.
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17.
  • Nilsson, Peter, et al. (författare)
  • Conformational transitions of a free amino-acid-functionalized polythiophene induced by different buffer systems
  • 2002
  • Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 14:42, s. 10011-10020
  • Tidskriftsartikel (refereegranskat)abstract
    • A chiral, 3-substituted polythiophene with an amino-acid function shows pH-dependent visible, emission and circular dichroism spectra in buffered aqueous solution. At pH equal to the pI of the amino-acid, the backbone adopts a nonplanar right-handed helical conformation and the polymer chains are separated from each other. Increasing pH leads to a more planar conformation of the backbone and an aggregation of the polymer chains occurs. A lower pH will also lead to a more planar conformation of the backbone, but aggregation of the polymer chains appears to be absent. The aggregates are disrupted by increasing ionic strength in alkaline buffer systems, indicating hydrogen bonding is important for aggregation. On the other hand, ions containing an amino group and one or more hydroxyl groups induce a more planar conformation of the polymer backbone.
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18.
  • 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.
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19.
  • Svensson, M., et al. (författare)
  • High-performance polymer solar cells of an alternating polyfluorene copolymer and a fullerene derivative
  • 2003
  • Ingår i: Advanced Materials. - : Wiley. - 0935-9648 .- 1521-4095. ; 15:12, s. 988-991
  • Tidskriftsartikel (refereegranskat)abstract
    • High-performance polymer solar cells of an alternating polyfluorene copolymer, PFDTBT, and a fullerene derivative were studied. It was shown that PFDTBT is a promising candidate for obtaining high energy conversion efficiency when combined with a suitable electron acceptor. Results showed that high-performance solar cells with extended spectral coverage and increased open-circuit voltage could be prepared from composites prepared from electron acceptor.
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20.
  • Svensson, M., et al. (författare)
  • Synthesis and properties of alternating polyfluorene copolymers with redshifted absorption for use in solar cells
  • 2003
  • Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 135-136, s. 137-138
  • Tidskriftsartikel (refereegranskat)abstract
    • Three fluorene based alternating copolymers with redshifted absorption were synthesized and used as the active layer in photodiodes. The polymers are soluble in common solvents. The photodiodes cover a large part of the solar spectrum with high external quantum efficiency and we reach 2.4% power conversion efficiency for the best device in this study. 
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  • Resultat 11-20 av 29

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