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Sökning: WAKA:ref > Inganäs Olle > Lunds universitet > Zigmantas D.

  • Resultat 1-6 av 6
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1.
  • Ruseckas, A., et al. (författare)
  • Luminescence from inter-chain aggregates in polythiophene films
  • 2001
  • Ingår i: Synthetic Metals. - Elsevier. - 0379-6779. ; 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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2.
  • Ruseckas, A, et al. (författare)
  • Luminescence quenching by inter-chain aggregates in substituted polythiophenes
  • 2001
  • Ingår i: Journal of Photochemistry and Photobiology, A: Chemistry. - Elsevier. - 1873-2666. ; 144:1, s. 3-12
  • Tidskriftsartikel (refereegranskat)abstract
    • Time-resolved photo luminescence spectra measured in solid films of two polythiophene derivatives with different chain packing allow to distinguish emission of intra-chain excitations from the luminescence of inter-chain aggregates. Aggregate luminescence is red shifted by about 0.1 eV relative to intra-chain emission and shows vibronic coupling to the C=C bond stretch with the Huang-Phys factor of S approximate to 1.5, which is twice bigger than that of the intra-chain emission. Combining time resolved luminescence data with femtosecond transient absorption, we show that the dynamic quenching of the luminescence in films with dense chain packing is mainly due to excitation energy transfer to aggregates. The radiative lifetime of the lowest excited state of the aggregate with the optical gap of 1.84-1.9 eV is estimated to be about 20 ns. The aggregate contribution to the total luminescence in the polythiophene films with dense chain packing is about 50% and does not change significantly with temperature. (C) 2001 Elsevier Science B.V. All rights reserved.
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3.
  • Theander, M., et al. (författare)
  • High luminescence from a substituted polythiophene in a solvent with low solubility
  • 2001
  • Ingår i: Chemical Physics Letters. - Elsevier. - 0009-2614. ; 337:4-6, s. 277-283
  • Tidskriftsartikel (refereegranskat)abstract
    • Steady-state and rime-resolved photoluminescence (PL) is used to probe different states of order in highly regular poly(3-(2'-methoxy-5'-octylphenyl)thiophene) (POMeOPT). In a good solvent (chloroform) the polymer has a PL yield of 0.33 and in a solvent with low solubility (mixture of chloroform and toluene) a new phase appears with higher PL yield (0.50). The new phase is attributed to micro-crystals formed by the regular part of the polymer which have low solubility in toluene. The crystallites have highly structured and redshifted electronic transitions compared with chains which are dissolved. (C) 2001 Published by Elsevier Science B.V.
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4.
  • Theander, M., et al. (författare)
  • Interchain photoluminescence in substituted polyfluorenes
  • 2001
  • Ingår i: Synthetic Metals. - Elsevier. - 0379-6779. ; 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.
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5.
  • Theander, M, et al. (författare)
  • Photoluminescence quenching at a polythiophene/C-60 heterojunction
  • 2000
  • Ingår i: Physical Review B (Condensed Matter and Materials Physics). - American Physical Society. - 1098-0121. ; 61:19, s. 12957-12963
  • Tidskriftsartikel (refereegranskat)abstract
    • Quenching of photoluminescence in a substituted polythiophene in the presence of a deposited C-60 layer is studied by steady-state and time-resolved photoluminescence (PL). The steady-state PL is evaluated by con -sidering the interference of the absorbed and emitted electro-optical field in the thin film coupled to exciton diffusion in the conjugated polymer. PL quenching occurs for excitons generated within 5 nm from the heterojunction. A blueshift of the polymer emission spectrum is observed when C-60 is deposited on top of a polymer thin film. The blueshift is shown to be caused by PL quenching before the excitation is transferred to the lowest-energy sites.
6.
  • Zaushitsyn, Y., et al. (författare)
  • Ultrafast light-induced charge pair formation dynamics in poly[3-(2 '-methoxy-5 ' octylphenyl)thiophene]
  • 2004
  • Ingår i: Physical Review B (Condensed Matter and Materials Physics). - American Physical Society. - 1098-0121. ; 70:7, s. 1-075202
  • Tidskriftsartikel (refereegranskat)abstract
    • Charge pair photogeneration was investigated by ultrafast absorption spectroscopy for different excitation photon energies in poly[3-(2(')-methoxy-5(')octylphenyl)thiophene] (POMeOPT) film with and without an external electric field. Electric field-assisted charge pair photogeneration in POMeOPT occurs from vibrationally relaxed singlet excitons during their entire lifetime and charge pair formation takes place in this manner even in the absence of an external electric field. From our data there are no indications of hot exciton dissociation to charge pairs even when a large amount of excess energy is supplied to the excitons. To explain these observations we present a model with energy transfer to low-barrier dissociation sites as a key feature.
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