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Sökning: WAKA:ref > Inganäs Olle > Andersson Mats > Perzon Erik > Chalmers tekniska högskola

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1.
  • Admassie, Shimelis, et al. (författare)
  • Electrochemical and optical studies of the band gaps of alternating polyfluorene copolymers
  • 2006
  • Ingår i: Synthetic Metals. ; 156:7-8, s. 614-623
  • Tidskriftsartikel (refereegranskat)abstract
    • The electrochemical and optical properties of a series of alternating polyfluorene copolymers with low band gaps were determined. These polymers incorporated fluorene units alternating with groups including electron-withdrawing (A) and electron-donating (D) groups in donor-acceptor-donor (DAD) sequence to achieve the lowering of band gaps. The polymers were solvent-casted on platinum disk electrode and the band gaps were estimated from cyclic voltammetry (CV). These values were compared with values obtained from optical absorption measurements. Although the electrochemically determined band gaps were found to be slightly higher than the optical band gap in most cases, values are well correlated. The values of the band gaps determined range from 2.1 to 1.3 eV. © 2006 Elsevier B.V. All rights reserved.
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2.
  • Chen, Miaoxiang, et al. (författare)
  • High carrier mobility in low band gap polymer-based field-effect transistors
  • 2005
  • Ingår i: Applied Physics Letters. - 0003-6951. ; 87:25, s. 252105-1-252105-3
  • Tidskriftsartikel (refereegranskat)abstract
    • A conjugated polymer with a low band gap of 1.21 eV, i.e., absorbing infrared light, is demonstrated as active material in field-effect transistors (FETs). The material consists of alternating fluorene units and low band gap segments with electron donor-acceptor-donor units composed of two electron-donating thiophene rings attached on both sides of a thiadiazolo-quinoxaline electron-acceptor group. The polymer is solution-processable and air-stable; the resulting FETs exhibit typical p-channel characteristics and field-effect mobility of 0.03 cm2 V−1 s−1.
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3.
  • Gadisa, Abay, et al. (författare)
  • Stoichiometry dependence of charge transport in polymer/methanofullerene and polymer/C70 derivative based solar cells
  • 2006
  • Ingår i: Organic electronics. - 1566-1199. ; 7:4, s. 195-204
  • Tidskriftsartikel (refereegranskat)abstract
    • Charge transport in a near infrared absorbing polyfluorene copolymer (APFO-Green1) and its blends with methanofullerene [6,6]-phenyl C61-butyric acid methyl ester (PCBM), and 3′-(3,5-bis-trifluoromethylphenyl)-1′-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) is reported. PCBM and BTPF70 are electron acceptor and transporting molecules in polymer based solar cells. The BTPF70 has emerged as a new electron acceptor molecule that provides adequate exciton dissociation when blended with the low band gap polyfluorene copolymer APFO-Green1. Electron transport in both net PCBM and BTPF70 films are subjected to positional and energetic disorder, with the degree of disorder being more pronounced in BTPF70. On the other hand, mixing PCBM with conjugated polymers usually leads to increased hole mobility. We have investigated and compared the acceptor concentration dependence of charge transport in APFO-Green1/PCBM and APFO-Green1/BTPF70 blend films. For better understanding of the charge transport in the heterojunction films, the field and temperature dependence of hole transport in pure APFO-Green1 films has also been studied. It is observed that the behavior of hole mobility in the blend layer is sensitive to the acceptor type. For APFO-Green1/PCBM hole only devices, the hole mobility attains a local maximum at 67 wt.% of PCBM, while on the contrary mixing any amount of BTPF70 with APFO-Green1 results into degradation of hole transport. Electron transport in both blends, however, increases monotonically as a function of acceptor loading.
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4.
  • J Lindgren, Lars, et al. (författare)
  • Synthesis, Characterization, and Devices of a Series of Alternating Copolymers for Solar Cells
  • 2009
  • Ingår i: CHEMISTRY OF MATERIALS. - 0897-4756. ; 21:15, s. 3491-3502
  • Tidskriftsartikel (refereegranskat)abstract
    • In this study we report the synthesis, characterization. and photovoltaic properties of a series of six Conjugated polymers based on donor-acceptor-donor (DAD) structure. The polymers are obtained via Suzuki polymerization of different alkoxy-substituted DAD monomers together with a substituted fluorene or phenylene monomer. Application of polymers as light-harvesting and electron-donating materials in solar cells, in conjunction with both [60]PCBM and [70]PCBM as acceptors, show power-conversion efficiencies (PCEs) up to 2.9%, values obtained without extensive optimization work. Furthermore, atomic force microscopy and field-effect transistor (FET) mobility measurements of acceptor-polymer mixtures show that differences in substitution on the polymers affect morphology, mobility, and device performance. Within the series of polymers, all showing similar optical absorption and redox behavior, substituents play an important role in phase separation on a micrometer scale, which in turn has a large impact on device performance. The phase-separation behavior is clearly seen in [70]PCBM devices where the best-performing devices are obtained using the polymers with short alkoxy groups or no substituents together with a high speed of spin coating during device preparation.
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5.
  • Perzon, Erik, 1977-, et al. (författare)
  • An alternating low band-gap polyfluorene for optoelectronic devices
  • 2006
  • Ingår i: Polymer. ; 47:12, s. 4261-4268
  • Tidskriftsartikel (refereegranskat)abstract
    • An alternating polyfluorene (APFO) with low band-gap segments. APFO-Green1, was synthesized for use in optoelectronic devices. The low band-gap segment consists of an electron acceptor (A), fenced by electron donors (D). This D-A-D configuration leads to partial charge transfer in the polymer backbone and a low band-gap of 1.3 eV. Characterization of APFO-Green1 include measurement of light absorption and emission at extended wavelengths and high hole mobility was found. Blends of the polymer with different fullerene derivs. exhibit unusually high photovoltaic performance at long wavelengths, making this type of conjugated polymers promising for application in plastic solar cells. [on SciFinder (R)]
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6.
  • Wang, Xiangjun, et al. (författare)
  • Enhanced photocurrent spectral response in low-bandgap polyfluorene and C70-Derivative-Based Solar Cells
  • 2005
  • Ingår i: Advanced Functional Materials. - 1616-301X. ; 15:10, s. 1665-1670
  • Tidskriftsartikel (refereegranskat)abstract
    • Plastic solar cells have been fabricated using a low-bandgap alternating copolymer of fluorene and a donor-acceptor-donor moiety (APFO-Green1), blended with 3<img src="http://www3.interscience.wiley.com/giflibrary/12/prime.gif" />-(3,5-bis-trifluoromethylphenyl)-1<img src="http://www3.interscience.wiley.com/giflibrary/12/prime.gif" />-(4-nitrophenyl)pyrazolino[70]fullerene (BTPF70) as electron acceptor. The polymer shows optical absorption in two wavelength ranges, <img src="http://www3.interscience.wiley.com/giflibrary/12/lambda.gif" /> &lt; 500 nm and 600 &lt; <img src="http://www3.interscience.wiley.com/giflibrary/12/lambda.gif" /> &lt; 1000 nm. The BTPF70 absorbs light at <img src="http://www3.interscience.wiley.com/giflibrary/12/lambda.gif" /> &lt; 700 nm. A broad photocurrent spectral response in the wavelength range 300 &lt; <img src="http://www3.interscience.wiley.com/giflibrary/12/lambda.gif" /> &lt; 1000 nm is obtained in solar cells. A photocurrent density of 3.4 mA cm-2, open-circuit voltage of 0.58 V, and power-conversion efficiency of 0.7 % are achieved under illumination of AM1.5 (1000 W m-2) from a solar simulator. Synthesis of BTPF70 is presented. Photoluminescence quenching and electrochemical studies are used to discuss photoinduced charge transfer.
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7.
  • Wang, Xiangjun, et al. (författare)
  • Polymer solar cells with low-bandgap polymers blended with C70-derivative give photocurrent at 1 μm
  • 2006
  • Ingår i: Thin Solid Films. - 0040-6090. ; 511-512, s. 576-580
  • Tidskriftsartikel (refereegranskat)abstract
    • A new series of low-bandgap alternating polyfluorenes with different donor–acceptor–donor moieties have been synthesized. Electrochemical and optical absorption measurement show that onset bandgaps of these polymers range from 1.2 to 1.5 eV. These polymers, blended with a C70-derivative as acceptor, are used for solar cell fabrication. Devices show promising photovoltaic properties, and the spectral response of photocurrent covers all visible and near-infrared wavelength regions with its onset extended to 1 μm. The best data gives a photocurrent density of 3.4 mA/cm2, open circuit voltage of 0.58 V and power conversion efficiency of 0.7% under illumination of AM1.5 (1000 W/m2) from a solar simulator.
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8.
  • Zhang, F. L., et al. (författare)
  • High photovoltage achieved in low band gap polymer solar cells by adjusting energy levels of a polymer with the LUMOs of fullerene derivatives
  • 2008
  • Ingår i: Journal of Materials Chemistry. - 0959-9428. ; 18:45, s. 5468-5474
  • Tidskriftsartikel (refereegranskat)abstract
    • Solar cells based on organic molecules or conjugated polymers attract great attention due to their unique advantages, such as low cost, and their use in flexible devices, but are still limited by their low power conversion efficiency (PCE). To improve the PCEs of polymer solar cells, more efforts have been made to increase short-circuit current (J(sc)) or open-circuit voltage (V-oc). However, the trade-off between J(sc) and V-oc in bulk heterojunctions solar cells makes it tricky to find a polymer with a low band gap to efficiently absorb photons in the visible and near infrared region of the solar spectrum, while maintaining a high V-oc in solar cells. Therefore, it is crucial to design and synthesize polymers with energy levels aligning with the LUMO (lowest unoccupied molecular orbital) of an electron acceptor to minimize the LUMO level difference between donor and acceptor to keep enough driving force for charge generation, thereby maximizing photovoltage in solar cells. Here a novel copolymer APFO-Green 9 was synthesized. Polymer solar cells based on APFO-Green 9 blended with a derivative of fullerene demonstrate high photovoltage by fine tuning the HOMO and LUMO level of APFO-Green 9. Solar cells based on APFO-Green 9 and [6,6]-phenyl-C71-butyric acid methyl ester ([70]PCBM) present a photoresponse extended to 900 nm with J(sc) of 6.5 mA cm(-2), V-oc of 0.81 V and PCE of 2.3% under illumination of AM1.5 with light intensity of 100 mW cm(-2). As a low band gap polymer with a V-oc bigger than 0.8 V, APFO-Green 9 is a promising candidate for efficient tandem solar cells.
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9.
  • Zhang, Fengling, et al. (författare)
  • Polymer Solar Cells Based on a Low-Bandgap Fluorence Copolymer and a Fullerene Derivative with Photocurrent Extended to 850 nm
  • 2005
  • Ingår i: Advanced Functional Materials. - 1616-301X. ; 15:5, s. 745-750
  • Tidskriftsartikel (refereegranskat)abstract
    • Polymer solar cells were fabricated from a low band-gap alternating polyfluorene copolymer, APFO-Green2, combined with [6,6]-phenyl-C61-butyric acid Me ester (PCBM), from org. solns. External quantum efficiencies of the solar cells show an onset at 850 nm and a peak of >10% located at 650 nm, which corresponds to the extended absorption spectrum of the polymer. A photocurrent of 3.0 mA/cm2, photovoltage of 0.78 V, and power conversion efficiency of 0.9% were obtained with solar cells based on this new low-bandgap polymer under an illumination of AM 1.5 (1000 W/m2) from a solar simulator. [on SciFinder (R)]
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