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Träfflista för sökning "WAKA:ref ;pers:(Inganäs Olle);pers:(Andersson Mats R);pers:(Zhou Yi)"

Sökning: WAKA:ref > Inganäs Olle > Andersson Mats R > Zhou Yi

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1.
  • Cai, Tianqi, 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)).
2.
  • Gedefaw, Desta A, et al. (författare)
  • Conjugated polymers with polar side chains in bulk heterojunction solar cell devices
  • 2014
  • Ingår i: Polymer international. - Wiley-Blackwell. - 0959-8103. ; 63:1, s. 22-30
  • Tidskriftsartikel (refereegranskat)abstract
    • Two polymers with polar side chains, namely poly[2,7-(9,9-dioctylfluorene)-alt-5,5-(5,8-di-2-thienyl-(2,3-bis(3-(2-(2-methoxyethoxy)ethoxy)phenyl)quinoxaline))] (P1) and poly[2,7-(9,9-bis(2-(2-methoxyethoxy)ethyl)fluorene)-alt-5,5-(5,8-di-2-thienyl-(2,3-bis(3-(2-(2-methoxyethoxy)-ethoxy)phenyl)quinoxaline))] (P2), were synthesized for solar cell application. A series of bulk heterojunction solar cells were systematically fabricated and characterized by varying the electron-acceptor materials, processing solvents and thickness of the active layer. The results show that P1, with a higher molecular weight and good film-forming properties, performed better. The best device showed an open circuit voltage of 0.87 V, a short circuit current of 6.81 mA cm(-2) and a power conversion efficiency of 2.74% with 1:4 polymer:[6,6]-phenyl-C71-butyric acid methyl ester (PCBM[70]) mixture using o-dichlorobenzene (o-DCB) as processing solvent. P2 on the other hand showed a poorer performance with chlorobenzene as processing solvent, but a much improved performance was obtained using o-DCB instead. Thus, an open circuit voltage of 0.80 V, short circuit current of 6.21 mA cm(-2) and an overall power conversion efficiency of 2.22% were recorded for a polymer:PCBM[70] mixing ratio of 1:4. This is presumably due to the improvement of the morphology of the active layer using o-DCB as processing solvent.
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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.
  • Müller, Christian, 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.
6.
  • Zhou, Yi, et al. (författare)
  • Black Polymers in Bulk-Heterojunction Solar Cells
  • 2010
  • Ingår i: IEEE JOURNAL OF SELECTED TOPICS IN QUANTUM ELECTRONICS. - Institute of Electrical and Electronics Engineers (IEEE). - 1077-260X. ; 16:6, s. 1565-1572
  • Tidskriftsartikel (refereegranskat)abstract
    • The active materials in polymer solar cells have a decisive role on the performance of the cells. Polymers with extended absorption, i.e., black polymers with absorption covering the whole visible region are desired in order to capture the important parts of the solar irradiation. Different ways of achieving black active materials are discussed and two new alternating polyfluorene (APFO) copolymers with broad absorption, APFO-Black 1 and APFO-Black 2, using two different design strategies are described. The UV-Vis absorption spectra of the polymers extend to approximately 850 nm, and the polymers were used as donors and [6,6]-phenyl-C-61-butyric acid methyl ester (PCBM)[60] or PCBM[70] as acceptors in solar cell devices in various mixing ratios. The best combinations yielded an overall power conversion efficiency of 1.2% for APFO-Black 1 and 1.5% for APFO-Black 2.
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7.
  • Zhou, Yi, et al. (författare)
  • Observation of a Charge Transfer State in Low-Bandgap Polymer/Fullerene Blend Systems by Photoluminescence and Electroluminescence Studies
  • 2009
  • Ingår i: ADVANCED FUNCTIONAL MATERIALS. - 1616-301X. ; 19:20, s. 3293-3299
  • Tidskriftsartikel (refereegranskat)abstract
    • The presence of charge transfer states generated by the interaction between the fullerene acceptor PCBM and two alternating copolymers of fluorene with donor-acceptor-donor comonomers are reported; the generation leads to modifications in the polymer bandgap and electronic structure. In one of polymer/fullerene blends, the driving; force for photocurrent generation, i.e., the gap between the lowest unoccupied molecular orbitals of the donor and acceptor, is only 0.1 eV, but photocurrent is generated. It is shown that the presence of a charge transfer state is more important than the driving force. The charge transfer states are visible through new emission peaks in the photoluminescence spectra and through electroluminescence at a forward bias. The photoluminescence can be quenched under reverse bias, and can be directly correlated to the mechanism of photocurrent generation. The excited charge transfer state is easily dissociated into free charge carriers, and is an important intermediate state through which free charge carriers are generated.
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