- 'Donor-free' oligo(3-hexylthiophene) dyes for efficient dye-sensitized solar cells
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The common trend in designing dyes for use in DSSCs with iodide-based electrolyte is based on a donor-π spacer-acceptor (D-π-A) architecture. Here, we report two 'donor-free' cyanoacrylic end-functionalized oligo(3-hexylthiophene) dyes (5T and 6T). Despite having no donor group, both dyes show reversible first oxidation process. Both 5T and 6T have n-hexyl alkyl chains to retard aggregation at different positions as well as different numbers of thiophene moieties. However, the dyes showed similar absorption properties and redox potentials. The DSSCs based on these dyes give power conversion efficiencies of more than 7%, although a significant difference in the VOC and FF has been observed. Using electrochemical impedance spectroscopy, this is attributed to the presence of more trap states when 6T attaches to TiO2 and modifies the surface, mainly affecting the fill factor. Overall, these dyes introduce a new and effective design concept for liquid-electrolyte DSSC sensitisers.
- Hu, Yue,Ivaturi, Aruna,Planells, Miquel,Boldrini, Chiara L.,Biroli, Alessio Orbelli,Robertson, Neil
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p. 2509 - 2516
(2016/02/20)
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- Supramolecular engineering of oligothiophene nanorods without insulators: Hierarchical association of rosettes and photovoltaic properties
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Supramolecular rosettes of oligothiophenes that do not bear long aliphatic tails have been designed as semiconducting nanomaterials for solution-processable bulk het-erojunction solar cells. The rosettes consist of six barbiturat-ed thienyl[oligo(hexylthiophene)] units (Bar-T-hTn; n = 3,4,5) aggregated by multiple hydrogen bonds, which have been directly visualized by scanning tunneling microscopy (STM) at a solid-liquid interface. 1H NMR spectroscopy in [D8]toluene showed that Bar-T-hTn exists as a mixture of monomers and small hydrogen-bonded aggregates. Hierarchical organization of the hydrogen-bonded aggregates took place through π - π stacking interactions upon casting their toluene solutions, resulting in the growth of highly ordered nanorods whose widths are consistent with the diameters of the rosettes. The nanorods could be generated in the presence of soluble fullerene derivatives via solution casting or the annealing of the resulting thin films. The solar cells fabricated based on these bulk heterojunction films showed power conversion efficiencies of 1-3%, which are far higher than those of the non-hydrogen-bonded reference oligothiophene and the derivative that possesses long aliphatic tails.
- Yagai, Shiki,Suzuki, Mika,Lin, Xu,Gushiken, Marina,Noguchi, Takuya,Karatsu, Takashi,Kitamura, Akihide,Saeki, Akinori,Seki, Shu,Kikkawa, Yoshihiro,Tani, Yuki,Nakayama, Ken-Ichi
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supporting information
p. 16128 - 16137
(2015/02/19)
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- Concise synthesis of well-defined linear and branched oligothiophenes with nickel-catalyzed regiocontrolled cross-coupling of 3-substituted thiophenes by catalytically generated magnesium amide
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The synthesis of linear and branched oligothiophenes of well-defined structures is performed with regioselective deprotonation of 3-substituted thiophenes and nickel-catalyzed cross-coupling of the thus formed metalated species with a bromothiophene. The reaction of 3-hexylthiophene with EtMgCl and 2,2,6,6-tetramethylpiperidine (TMP-H, 10 mol %) induces the metalation selectively at the 5-position by use of the catalytically generated hindered magnesium amide (TMPMgCl) and the subsequent reaction of a 2-halo-3- hexylthiophene (bromide or chloride) in the presence of a nickel catalyst affords a head-to-tail (HT)-type dimer. By repeating the same sequence, the linear oligothiophene up to a 4-mer is synthesized in good yield. The reaction of 3-hexylthiophene with 2,3-dibromothiophene also takes place to afford a branched oligothiophene 3-mer in quantitative yield. The obtained 3-mer is also metalated at the sterically less-hindered position in a regioselective manner furnishing a 7-mer in >99 % yield after a further coupling reaction with 2,3-dibromothiophene. These dendrimers react with several multifunctionalized organic electrophiles, leading to a variety of branched oligothiophenes. Copyright
- Tanaka, Shota,Tanaka, Daiki,Tatsuta, Go,Murakami, Kohei,Tamba, Shunsuke,Sugie, Atsushi,Mori, Atsunori
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supporting information
p. 1658 - 1665
(2013/02/25)
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- "fibonacci's route" to regioregular oligo(3-hexylthiophene)s
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We describe a new synthetic approach to regioregular monodisperse oligo(3-alkylthiophene)s allowing for simple separation of regioregular material in gram quantities. The number of repeat units follows the Fibonacci numbers up to a length of 21. In a small adaption of this approach, introduction of a protecting group was used to synthesize an oligo(3-hexylthiophene) with 36 repeating units, the longest regioregular 3-hexylthiophene oligomer synthesized to date.
- Koch, Felix P. V.,Smith, Paul,Heeney, Martin
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p. 13695 - 13698
(2013/10/01)
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- Synthesis of well-defined head-to-tail-type oligothiophenes by regioselective deprotonation of 3-substituted thiophenes and nickel-catalyzed cross-coupling reaction
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Iterative growth of thiophene oligomers by single-step extensions has been realized by regioselective metalation of 3-substituted thiophenes with the Knochel-Hauser base (TMPMgCl·LiCl) and coupling with bromothiophene using a nickel catalyst. Treatment of 3-hexylthiophene with TMPMgCl·LiCl induces metalation at the 5-position selectively. Subsequent addition of 2-bromo-3-hexylthiophene and a nickel catalyst leads to the corresponding bithiophene. The obtained bithiophene is converted to the terthiophene and then to the quaterthiophene by repeating the similar protocol. A concise synthesis of MK-1 and MK-2, which are organic dye molecules bearing an oligothiophene moiety that are used in photovoltaic cells, has been achieved.
- Tanaka, Shota,Tamba, Shunsuke,Tanaka, Daiki,Sugie, Atsushi,Mori, Atsunori
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supporting information; experimental part
p. 16734 - 16737
(2011/12/14)
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