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Träfflista för sökning "WAKA:ref ;pers:(Inganäs Olle);srt2:(2010-2011)"

Sökning: WAKA:ref > Inganäs Olle > (2010-2011)

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1.
  • Andersson, Mattias, et al. (författare)
  • Mobility and fill factor correlation in geminate recombination limited solar cells
  • 2011
  • Ingår i: Journal of Applied Physics. - American Institute of Physics (AIP). - 0021-8979. ; 110:2, s. 024509
  • Tidskriftsartikel (refereegranskat)abstract
    • Empirical data for the fill factor as a function of charge carrier mobility for two different polymer: fullerene systems is presented and analyzed. The results indicate that charge extraction depth limitations and space charge effects are inconsistent with the observed behavior, and the decrease in the fill factor is, instead, attributed to the field-dependent charge separation and geminate recombination. A solar cell photocurrent limited by the Onsager-Braun charge transfer exciton dissociation is shown to be able to accommodate the experimental observations. Charge dissociation limited solar cells always benefit from increased mobilities, and the negative contribution from the reduced charge separation is shown to be much more important for the fill factor in these material systems than any adverse effects from charge carrier extraction depth limitations or space charge effects due to unbalanced mobilities. The logarithmic dependence of the fill factor on the mobility for such a process is also shown to imply that simply increasing the mobilities is an impractical way to reach very high fill factors under these conditions since unrealistically high mobilities are required. A more controlled morphology is, instead, argued to be necessary for high performance.
2.
  • Andersson, Viktor, et al. (författare)
  • Full day modelling of V-shaped organic solar cell
  • 2011
  • Ingår i: Solar Energy. - Elsevier Science B.V., Amsterdam.. - 0038-092X. ; 85:6, s. 1257-1263
  • Tidskriftsartikel (refereegranskat)abstract
    • Folded and planar solar cells are examined with optical simulations, with the finite element method. The maximum photocurrent densities during the full day are compared between cells of different geometries and tilting angles. The change of incident angle and spectrum over time are handled in this analysis. The results show that the light trapping effect of the folded cell makes these cells show higher maximum photocurrent densities than the planar cells during all hours of the day. This is the case for both single and tandem cells. The results also indicate that balancing the currents in the tandem cells by adjusting the active layer thickness may be more cumbersome with the folded tandem cells than the stacked planar cells.
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3.
  • Björk, Per, et al. (författare)
  • Biomolecular nanowires decorated by organic electronic polymers
  • 2010
  • Ingår i: JOURNAL OF MATERIALS CHEMISTRY. - 0959-9428. ; 20:12, s. 2269-2276
  • Tidskriftsartikel (refereegranskat)abstract
    • We demonstrate the shaping and forming of organic electronic polymers into designer nanostructures using biomacromolecules. In order to create nanowires, nanohelixes and assemblies of these, we coordinate semiconducting or metallic polymers to biomolecular polymers in the form of DNA and misfolded proteins. Optoelectronic and electrochemical devices utilizing these shaped materials are discussed.
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4.
  • 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)).
5.
  • Gadisa, Abay, et al. (författare)
  • Bipolar Charge Transport in Fullerene Molecules in a Bilayer and Blend of Polyfluorene Copolymer and Fullerene
  • 2010
  • Ingår i: ADVANCED MATERIALS. - 0935-9648. ; 22:9, s. 1008
  • Tidskriftsartikel (refereegranskat)abstract
    • Efficient polymer solar cells typically contain the fullerene derivative [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), which promotes dissociation of excited states and enhances charge transport. The ability of PCBM to transport holes in solar cell bulk heterojunction films is monitored via the electroluminescence emission of a bulk heterojunction blend of PCBM and a polyfluorene copolymer. In polymer/fullerene bilayer diodes, fullerene emission is also observed.
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6.
  • He, Youjun, et al. (författare)
  • Poly(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b ]dithiophene vinylene): Synthesis, Optical and Photovoltaic Properties
  • 2010
  • Ingår i: JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY. - John Wiley and Sons, Ltd. - 0887-624X. ; 48:8, s. 1822-1829
  • Tidskriftsartikel (refereegranskat)abstract
    • A new benzodithiophene (BDT)-based polymer, poly(4,8-bis(2-ethylhexyloxy)benzo[1,2-b:4,5-b]dithiophene vinylene) (PBDTV), was synthesized by Pd-catalyzed Stille-coupling method. The polymer is soluble in common organic solvents and possesses high thermal stability. PBDTV film shows a broad absorption band covering from 350 nm to 618 nm, strong photoluminescence peaked at 545 nm and high hole mobility of 4.84 x 10(-3) cm(2)/Vs. Photovoltaic properties of PBDTV were studied by fabricating the polymer solar cells based on PBDTV as donor and PC70BM as acceptor. With the weight ratio of PBDTV: PC70BM of 1:4 and the active layer thickness of 65 nm, the power conversion efficiency of the device reached 2.63% with V-oc = 0.71 V, I-sc = 6.46 mA/cm(2), and FF = 0.57 under the illumination of AM1.5, 100 mW/cm(2).
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7.
  • 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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8.
  • 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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9.
  • 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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10.
  • 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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