| 1. |
- Andersson, M.R., et al.
(författare)
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The effect of the polymerisation temperature on molecular weight and photoluminescence quantum yield for a phenylsubstituted PPV
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 119:1-3, s. 63-64
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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.
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| 2. |
- Gillissen, S, et al.
(författare)
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Synthesis and characterization of poly(pyridine vinylene) via the sulfinyl precursor route
- 2001
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 34:21, s. 7294-7299
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of poly(pyridine vinylene) (PPyV) via the nonionic sulfinyl precursor route is presented. Starting from an unsymmetrical monomer, precursor polymers were prepared in various solvents, which led to polymers with variable molecular weights. The thermal conversion to the conjugated structure, as well as its stability, was studied with different techniques such as FT-IR, UV-vis, TGA, and direct insertion probe mass spectroscopy (DIP-MS). From these results we were able to derive the most suitable conditions to perform the conversion. The fully conjugated PPyV was further characterized with photoluminescence (PL) and cyclic voltammetry (CV) measurements. The PL efficiency was found to be as high as 14%. The CV measurements showed that the polymer can be reduced (n-doped).
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| 3. |
- Grage, M.M.-L., et al.
(författare)
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Conformational disorder of a substituted polythiophene in solution revealed by excitation transfer
- 2001
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Ingår i: Chemical Physics Letters. - 0009-2614 .- 1873-4448. ; 339:1-2, s. 96-102
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Tidskriftsartikel (refereegranskat)abstract
- Anisotropy and isotropic transient absorption decays of a polythiophene derivative in dilute solution have been measured and compared to calculated decays on Monte Carlo simulated polymer chains to obtain knowledge about the geometrical conformation of the polymer. The polymer chain conformations are generated by a partially correlated self-avoiding random walk. Excitation migration along the isolated chain is modeled assuming a hopping mechanism. This approach can be used to determine conformational disorder and possible realizations of the polymer chains in solution as well as the trapping time and migration length of the excitation. © 2001 Elsevier Science B.V.
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| 4. |
- Inganäs, Olle, et al.
(författare)
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Optical emission from confined poly(thiophene) chains
- 1998
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Ingår i: Optical materials (Amsterdam). - : Elsevier. - 0925-3467 .- 1873-1252. ; 9:1-4, s. 104-108
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Tidskriftsartikel (refereegranskat)abstract
- We discuss the stages of the luminescence processes in substituted and soluble poly(thiophenes), using results from determinations of absolute quantum yields of photoluminescence, fast pump-probe experiments and microcavity devices. Enhancement of the quantum yield of photoluminescence, with poly(thiophenes) in the solid state, call be obtained by dispersing the conjugated chain in a molecularly dispersed polymer blend, or by adding side chains designed for forcing the conjugated main chains apart. At the wavelength of stimulated emission, we observe a narrow bandwidth emission in the high-Q one-dimensional microcavity devices prepared by sandwiching two dielectric mirrors around a thin polymer film, A strong enhancement of the power efficiency is observed at a pump power of 1 mu W/cm(2), but does not conclusively show lasing characteristics. (C) 1998 Elsevier Science B.V.
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| 5. |
- Johansson, DM, et al.
(författare)
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Influence of polymerization temperature on molecular weight, photoluminescence, and electroluminescence for a phenyl-substituted poly(p-phenylenevinylene)
- 2001
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Ingår i: Macromolecules. - 0024-9297 .- 1520-5835. ; 34:11, s. 3716-3719
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterization of poly(2-(2",5'-bis(2"-ethylhexyloxy)phenyl)-1,4-phenylenevinylene) (BEHP-PPV) polymerized at different temperatures. The photoluminescence efficiencies in the solid state of BEHP-PPV obtained at 144 and 0 degreesC are 28% and 60%, respectively. H-1 NMR measurements showed a lower concentration of structural defects for BEHP-PPV obtained at lower temperatures, which can explain the increased photoluminescence efficiencies for these polymers. Polymerization temperatures below 0 degreesC decrease the molecular weight without changing the photoluminescence efficiency to any large extent. The electroluminescence efficiencies follow the trend in the photoluminescence efficiencies.
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| 6. |
- Johansson, D.M., et al.
(författare)
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Convenient synthetic route to poly(p-phenylene-1,2-diphenylvinylenes)
- 2000
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 113:3, s. 293-297
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of two soluble poly(p-phenylenevinylene)s substituted with phenyl groups on the vinylene moiety is reported. The polymers are poly(1,4-phenylene-1,2-diphenylvinylene) (PPV-DP) and poly(1,4-phenylene-1,2-(3'-(2?-ethylhexyloxy))-diphenylvinylene) (PPV-mEHDP). The monomers containing chloromethyl groups were polymerized with excess potassium tert-butoxide in dioxane at room temperature. The polymerization conditions are optimized. The photoluminescence (PL) properties of the polymers showed an increase in the PL efficiency in film from 19% for PPV-DP to 37% for PPV-mEHDP. Both polymers emitted green light with higher intensity in film than in solution.
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| 7. |
- Johansson, D.M., et al.
(författare)
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Synthesis and characterisation of polyfluorenes with light-emitting segments
- 2001
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Ingår i: Synthetic metals. - 0379-6779 .- 1879-3290. ; 121:1-3, s. 1761-1762
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterisation of two copolymers. They consists of poly(9-hexyl-9-(2'-ethylhexyl)fluorene) (HEH-PF) with a small amount of another polymer with a narrow band-gap. The synthetic route was designed to allow the incorporation of only one low band-gap segment per polymer chain. Photoluminescence measurements showed that energy transfer from the PF-segments to the low band-gap segments, did occur. In the solid state, all emissions were detected from the low band-gap segments with photoluminescence quantum yields up to 68%. One copolymer showed a low threshold for lasing (2 µJ/cm2) in a microcavity device.
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| 8. |
- Johansson, D.M., et al.
(författare)
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Synthesis and characterization of highly soluble phenyl-substituted poly(p-phenylenevinylenes)
- 2000
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 33:7, s. 2525-2529
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Tidskriftsartikel (refereegranskat)abstract
- We present the synthesis and characterization of soluble, high molecular weight phenyl-substituted poly(p-phenylenevinylenes). The studied polymers are poly(2-(2',5'-bis(2?-ethylhexyloxy)phenyl)- 1,4-phenylenevinylene) (BEHP-PPV) and copolymers of BEHP-PPV and poly(2-methoxy-5-(2'-ethylhexyloxy)-1,4-phenylenevinylene) (MEH-PPV). Their photoluminescence and electroluminescence have been examined as well as their stability to air and light. The polymers emitted green and yellow light. Stability measurements showed increased stability compared to some previously known substituted PPVs.
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| 9. |
- Johansson, DM, et al.
(författare)
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Synthesis and characterization of polyfluorenes with light-emitting segments
- 2001
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Ingår i: Macromolecules. - 0024-9297 .- 1520-5835. ; 34:6, s. 1981-1986
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Tidskriftsartikel (refereegranskat)abstract
- Two new polymers consisting of poly(9-(2'-ethylhexyl)-9-hexylfluorene) (EHH-PF) with a small amount of substituted poly(p-phenylenevinylene) (PPV) segments have been synthesized and characterized. The synthetic route was designed to allow the incorporation of only one (or zero) PPV segments per polymer chain. Photoluminescence measurements showed that energy transfer from the PF segments to the more narrow band-gap PPV segments did occur, both in solution and in film. In the solid state, all emissions were detected from the PPV segments with photoluminescence quantum yields up to 68%. One of the polymers has been used as the active material in a microcavity laser device. The threshold for lasing is 2 muJ/cm(2).
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| 10. |
- Roman, LS, et al.
(författare)
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Photovoltaic devices based on photo induced charge transfer in polythiophene : CN-PPV blends
- 2003
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Ingår i: Brazilian journal of physics. - 0103-9733 .- 1678-4448. ; 33:2, s. 376-381
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Tidskriftsartikel (refereegranskat)abstract
- We have investigated the photovoltaic properties of polymer devices based on a blend of two polymers, (poly(3-(2'-methoxy-5'-octylphenyl) thiophene) (POMeOPT) and poly(2,5,2',5'-tetrahexyloxy-7,8'-dicyanodi-p-phenylenevinylene) (CN-PPV), where photo induced charge transfer takes place at the interfaces formed by the interpenetrating network of the donor and the acceptor. The polymer blend films resulting from the spin coating were phase separated and the photo response of the devices depended on the morphology of the segregation. We have studied different blend ratios by photoluminescence quenching, scanning force microscopy and photovoltaic measurements. External quantum efficiencies of 4.5% at 500nm were achieved for the less segregated polymer blend.
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