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Sökning: WAKA:ref > Inganäs Olle > (2010-2011) > Andersson Mats R > Linköpings universitet

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1.
  • Hou, L. T., et al. (författare)
  • Lateral Phase Separation Gradients in Spin-Coated Thin Films of High-Performance Polymer: : Fullerene Photovoltaic Blends
  • 2011
  • Ingår i: Advanced Functional Materials. - Wiley-VCH Verlag Berlin. - 1616-301X. ; 21:16, s. 3169-3175
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study, it is demonstrated that a finer nanostructure produced under a rapid rate of solvent removal significantly improves charge separation in a high-performance polymer: fullerene bulk-heterojunction blend. During spin-coating, variations in solvent evaporation rate give rise to lateral phase separation gradients with the degree of coarseness decreasing away from the center of rotation. As a result, across spin-coated thin films the photocurrent at the first interference maximum varies as much as 25%, which is much larger than any optical effect. This is investigated by combining information on the surface morphology of the active layer imaged by atomic force microscopy, the 3D nanostructure imaged by electron tomography, film formation during the spin coating process imaged by optical interference and photocurrent generation distribution in devices imaged by a scanning light pulse technique. The observation that the nanostructure of organic photovoltaic blends can strongly vary across spin-coated thin films will aid the design of solvent mixtures suitable for high molecular-weight polymers and of coating techniques amenable to large area processing.
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2.
  • Cai, T. Q., et al. (författare)
  • Low bandgap polymers synthesized by FeCl(3) oxidative polymerization
  • 2010
  • Ingår i: Solar Energy Materials and Solar Cells. - 0927-0248. ; 94:7, s. 1275-1281
  • Tidskriftsartikel (refereegranskat)abstract
    • Four low bandgap polymers, combining an alkyl thiophene donor with benzo[c][1,2,5]thiadiazole, 2,3-diphenylquinoxaline, 2,3-diphenylthieno[3,4-b]pyrazine and 6,7-diphenyl-[1,2,5]thiadiazolo[3,4-g] quinoxaline acceptors in a donor-acceptor-donor architecture, were synthesized via FeCl3 oxidative polymerization. The molecular weights of the polymers were improved by introducing o-dichlor-obenzene (ODCB) as the reaction solvent instead of the commonly used solvent, chloroform. The photophysical, electrochemical and photovoltaic properties of the resulting polymers were investigated and compared. The optical bandgaps of the polymers vary between 1.0 and 1.9 eV, which is promising for solar cells. The devices spin-coated from an ODCB solution of P1DB:[70]PCBM showed a power conversion efficiency of 1.08% with an open-circuit voltage of 0.91 V and a short-circuit current density of 3.36 mA cm(-2) under irradiation from an AM1.5G solar simulator (100 mW cm(-2)).
3.
  • Hellstrom, Stefan, et al. (författare)
  • Influence of side chains on electrochromic properties of green donor-acceptor-donor polymers
  • 2011
  • Ingår i: Electrochimica Acta. - 0013-4686. ; 56:10, s. 3454-3459
  • Tidskriftsartikel (refereegranskat)abstract
    • Three solution processable cathodically coloring green electrochromic polymers, based on 2,3-diphenyl-5,7-di(thiophen-2-yl)thieno[3,4-b]pyrazine, have been synthesized by oxidative FeCl3 polymerization. The polymers were designed with solubilizing alkyl and oligoethylene oxide side chains to achieve solubility and processability. All three polymers have a small electrochemical bandgap (1.8-1.9 eV) and low oxidation potentials. Spectroelectrochemical studies of polymer films on ITO reveal that the alkyl side chains in head-to-head position on the polymer backbone promote a defined high-energy absorption peak and suppress tailing of charge-carrier absorption into the visible region. Kinetic studies, based on transmission measurements applying a square-wave potential between reduced and oxidized states, show that the polymer with exclusively oligoethylene oxide side chains (P3) had the fastest response times, monitored at the low-energy absorption maxima. The best performing polymer (P1) showed a good optical contrast in the visible region with a Delta T of 26% at 700 nm. An initial test of the electrochemical stability showed that the oligoethylene oxide containing polymers had superior stability over 500 full switches.
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4.
  • Hellstrom, Stefan, et al. (författare)
  • Synthesis and characterization of three small band gap conjugated polymers for solar cell applications
  • 2010
  • Ingår i: Polymer Chemistry. - 1759-9954. ; 1:8, s. 1272-1280
  • Tidskriftsartikel (refereegranskat)abstract
    • We report on a new series of small band gap conjugated polymers utilizing donor-acceptor-donor substructures in the polymer backbone to broaden and extend the optical absorption to longer wavelengths. Three polymers were prepared by Suzuki polymerization, using the same donor-acceptor-donor segment but with different comonomers. The goal was to investigate how the optical and electronic properties of the polymers were influenced by the different comonomers. Electrochemical spectroscopy, using square-wave voltammetry, shows that increasing the electron-donating strength of the comonomer will raise the HOMO energy level of the polymer, resulting in a decreased band gap. This result is also manifested by comparing open-circuit voltages from the corresponding laboratory fabricated solar cells. The best performing photovoltaic cell, based on APFO-Green15/[60]PCBM (1 : 4 w/w), reached a J(sc) of 4.2 mA cm(-2), a V-oc of 0.73 V, and a FF of 0.54, giving a PCE of 1.7%.
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5.
  • Inganäs, Olle, et al. (författare)
  • Polymer Photovoltaics with Alternating Copolymer/Fullerene Blends and Novel Device Architectures
  • 2010
  • Ingår i: Advanced Materials. - 0935-9648. ; 22:20, s. 100-116
  • Tidskriftsartikel (refereegranskat)abstract
    • The synthesis of novel conjugated polymers, designed for the purpose of photovoltaic energy conversion, and their properties in polymer/fullerene materials and photovoltaic devices are reviewed. Two families of main chain polymer donors, based on fluorene or phenylene and donor-acceptor-donor comonomers in alternating copolymers, are used to absorb the high-energy parts of the solar spectrum and to give high photovoltages in combinations with fullerene acceptors in devices. These materials are used in alternative photovoltaic device geometries with enhanced light incoupling to collect larger photocurrents or to enable tandem devices and enhance photovoltage.
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6.
  • Muller, C., et al. (författare)
  • Influence of Molecular Weight on the Performance of Organic Solar Cells Based on a Fluorene Derivative
  • 2010
  • Ingår i: Advanced Functional Materials. - 1616-301X. ; 20:13, s. 2124-2131
  • Tidskriftsartikel (refereegranskat)abstract
    • The performance of organic photovoltaic (OPV) bulk-heterojunction blends comprising a liquid-crystalline fluorene derivative and a small-molecular fullerene is found to increase asymptotically with the degree of polymerization of the former. Similar to various thermodynamic transition temperatures as well as the light absorbance of the fluorene moiety, the photocurrent extracted from OPV devices is found to strongly vary with increasing oligomer size up to a number average molecular weight, M-n approximate to 10 kg mol(-1), but is rendered less chain-length dependent for higher M-n as the fluorene derivative gradually adopts polymeric behavior.
7.
  • Pal, S. K., et al. (författare)
  • Geminate Charge Recombination in Polymer/Fullerene Bulk Heterojunction Films and Implications for Solar Cell Function
  • 2010
  • Ingår i: Journal of the American Chemical Society. - 0002-7863. ; 132:35, s. 12440-12451
  • Tidskriftsartikel (refereegranskat)abstract
    • We have studied the influence of three different fullerene derivatives on the charge generation and recombination dynamics of polymer/fullerene bulk heterojunction (BHJ) solar cell blends. Charge generation in APFO3/[70]PCBM and APFO3/[60]PCBM is very similar and somewhat slower than charge generation in APFO3/[70]BTPF. This difference qualitatively matches the trend in free energy change of electron transfer estimated from the LUMO energies of the polymer and fullerene derivatives. The first order (geminate) charge recombination rate is significantly different for the three fullerene derivatives studied and increases in the order APFO3/[70]PCBM andlt; APFO3/[60]PCBM andlt; APFO3/[70]BTPF. The variation in electron transfer rate cannot be explained from the LUMO energies of the fullerene derivatives and single-step electron transfer in the Marcus inverted region and simple considerations of expected trends for the reorganization energy and free energy change. Instead we suggest that geminate charge recombination occurs from a state where electrons and holes have separated to different distances in the various materials because of an initially high charge mobility, different for different materials. In a BHJ thin film this charge separation distance is not sufficient to overcome the electrostatic attraction between electrons and holes and geminate recombination occurs on the nanosecond to hundreds of nanoseconds time scale. In a BHJ solar cell, we suggest that the internal electric field in combination with polarization effects and the dynamic nature of polarons are key features to overcome electron-hole interactions to form free extractable charges.
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8.
  • Rizzo, Aurora, et al. (författare)
  • White Light with Phosphorescent Protein Fibrils in OLEDs
  • 2010
  • Ingår i: Nano Letters. - 1530-6984. ; 10:6, s. 2225-2230
  • Tidskriftsartikel (refereegranskat)abstract
    • Red and yellow phosphorescent insulin amyloid fibrils are used as guest-emitting species within a blue-emitting polyfluorene matrix in light-emitting diodes. The integration of the phosphorescent Ir-complex into the amyloid structures strongly improves the triplet exciton confinement and allows the fabrication of white-emitting device with a very low loading of phosphorescent complex. The overall performances of the devices are improved in comparison with the corresponding bare Ir-complexes. This approach opens a way to explore novel device architectures and to understand the exciton/charge transfer dynamics in phosphorescent light emitting diodes.
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9.
  • Wang, Ergang, 1981-, et al. (författare)
  • An Easily Accessible Isoindigo-Based Polymer for High-Performance Polymer Solar Cells
  • 2011
  • Ingår i: Journal of the American Chemical Society. - 0002-7863. ; 133:36, s. 14244-14247
  • Tidskriftsartikel (refereegranskat)abstract
    • A new, low-band-gap alternating copolymer consisting of terthiophene and isoindigo has been designed and synthesized. Solar cells based on this polymer and PC(71)BM show a power conversion efficiency of 6.3%, which is a record for polymer solar cells based on a polymer with an optical band gap below 1.5 eV. This work demonstrates the great potential of isoindigo moieties as electron-deficient units for building donor-acceptor-type polymers for high-performance polymer solar cells.
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10.
  • Wang, Ergang, et al. (författare)
  • An Easily Synthesized Blue Polymer for High-Performance Polymer Solar Cells
  • 2010
  • Ingår i: ADVANCED MATERIALS. - John Wiley and Sons, Ltd. - 0935-9648. ; 22:46, s. 5240-5244
  • Tidskriftsartikel (refereegranskat)abstract
    • High performance solar cells fabricated from an easily synthesized donor-acceptor polymer show maximum power point up to 6.0 mW cm(-2), with an open-circuit voltage of 0.89 V, short-circuit current density of 10.5 mA cm(-2) and fill factor of 0.64, making this polymer a particularly promising candidate for high-efficiency low-cost polymer solar cells.
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