| 1. |
- Chen, LC, et al.
(författare)
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Excitation transfer in polymer photodiodes for enhanced quantum efficiency
- 2000
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Ingår i: Advanced Materials. - 0935-9648 .- 1521-4095. ; 12:15, s. 1110-
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Tidskriftsartikel (refereegranskat)abstract
- The realization of polymer solar cells is the driving force behind this research. In an idea inspired by photosynthesis, the authors have constructed efficient bilayer photodiodes by a well-chosen combination of conjugated polymers (see Figure) in the donor layer. Forster energy transfer within the donor layer allows the absorbed light to be channeled to the C-60 acceptor layer, improving the total photoconversion of the blend device.
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| 2. |
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| 3. |
- 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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| 4. |
- Godovsky, D, et al.
(författare)
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The use of combinatorial materials development for polymer solar cells
- 2000
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Ingår i: Advanced Materials for Optics and Electronics. - 1057-9257 .- 1099-0712. ; 10:2, s. 47-54
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Tidskriftsartikel (refereegranskat)abstract
- Vile use a combinatorial approach to develop molecular plastic solar cells based on soluble fullerene derivatives blended with conjugated polymers. A combinatorial way of sample preparation is well suited to deal with the multitude of possible combinations of the components of such blends. We use high mobility poly(thiophene) and poly(phenylenevinylene) derivatives to be combined with accepters, Gradients of methanofullerene/polymer concentration were formed by diusion of the low molecular weight component in the spin-cast polymer matrix, Likewise the gradients of zinc phthalocyanine/C-60 were prepared by co-evaporation of the two materials from two sources to make a linear array of photodiode devices, Photo- and electrophysical properties, such as absorption, luminescence, short circuit photocurrent and open circuit photovoltage, were measured using a specially designed installation with a resolution of 70-100 mu. Clear evidence was obtained that the photoconversion efficiency increased with the amount of methanofullerene up to very high levels, in the case of methanofullerene/polymer blends, verifying the important role of the acceptor in the photoconversion. By choosing the optimal ratio between C-60 and ZnPc in the evaporated layer it Is possible to obtain high photocurrent in the 600-700 nm range, due to the added contribution from photoinduced electron transfer between the two molecules, Copyright (C) 2000 John Wiley & Sons, Ltd.
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| 5. |
- Granlund, T, et al.
(författare)
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Luminescence probing of crystallization in a polymer film
- 2000
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Ingår i: Journal of Applied Physics. - 0021-8979 .- 1089-7550. ; 87:12, s. 8549-8556
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Tidskriftsartikel (refereegranskat)abstract
- We report studies of a thin film multilayer stack including a highly emissive substituted polythiophene, poly[3-(2,5-dioctylphenyl)thiophene]. Analysis of the photoluminescence spectra revealed an inhomogeneous polymer film. X-ray diffraction studies attribute the existence of an inhomogeneous film as originating from crystallization of the polymer. We used the interference effect of light to detect the region of crystallization in the film. Photoluminescence and absorption were redshifted upon crystallization and displayed an enhanced vibronic structure. Comparison between calculated and measured photoluminescence shows that the crystallization starts from the top of the film and not from the supporting substrate. (C) 2000 American Institute of Physics. [S0021- 8979(00)08112-3].
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| 6. |
- 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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| 7. |
- 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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| 8. |
- 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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| 9. |
- Johansson, DM, et al.
(författare)
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Synthesis of soluble phenyl-substituted poly(p-phenylenevinylenes) with a low content of structural defects
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:13, s. 4997-5003
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Tidskriftsartikel (refereegranskat)abstract
- The synthesis and characterization of two new soluble poly(p-phenylenevinylenes) (PPVs) are reported. The polymers are poly(2-2',5'-bis(octyloxy)benzene)-1,4-phenylenevinylene) (BOP-PPV) and poly(2-(2',5'-bis(octyloxy)benzene)-5-methoxy-1,4-phenylenevinylene) (BOPM-PPV). Both polymers have been polymerized at high and low temperatures to study the formation of structural defects. It is shown that both methoxy groups as side chains and low polymerization temperatures decrease the content of defects in the final polymer. As a consequence, the polymers with lower concentration of defects exhibit higher electroluminescence yields in light-emitting diodes. In addition to this, the polymers with a low content of defects exhibited longer operational lifetimes in these devices. The highest photoluminescence quantum yield in the solid state and electroluminescence efficiency were found to be 72% and 1.74%, respectively.
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| 10. |
- Jonforsen, M, et al.
(författare)
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Synthesis and characterization of soluble and n-dopable poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with relatively small band gap
- 2002
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 35:5, s. 1638-1643
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Tidskriftsartikel (refereegranskat)abstract
- Synthesis and characterization of poly(quinoxaline vinylene)s and poly(pyridopyrazine vinylene)s with linear and branched aliphatic side chains are reported. The electron affinity of the polymers was measured with cyclic voltammetry (CV) and found to be highest for the pyridopyrazine vinylene polymers, Compared to CN-MEH-PPV, the pyridopyrazine vinylene polymers were easier to reduce, while the quinoxaline derivatives were harder. UV-vis absorption measurements showed that the polymers have relatively small band gaps.
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