Supramolecular Engineering of Oligothiophene Nanorods without Insulators: Hierarchical Association of Rosettes and Photovoltaic Properties |
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Authors: | Prof?Dr Shiki Yagai Mika Suzuki Dr Xu Lin Marina Gushiken Takuya Noguchi Prof?Dr Takashi Karatsu Prof?Dr Akihide Kitamura Prof?Dr Akinori Saeki Prof?Dr Shu Seki Dr Yoshihiro Kikkawa Yuki Tani Prof?Dr Ken‐ichi Nakayama |
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Institution: | 1. Department of Applied Chemistry and Biotechnology, Graduate School of Engineering, Chiba University, 1‐33 Yayoi‐cho, Inage‐ku, Chiba 263‐8522 (Japan), Fax: (+81)?43‐290‐3039;2. CREST, JST, Chiyoda‐ku, Tokyo 102‐0075 (Japan);3. Department of Applied Chemistry, Graduate School of Engineering, Osaka University, 2‐1, Yamadaoka, Suita, Osaka 565‐0871 (Japan);4. National Institute of Advanced Industrial Science and Technology (AIST), 1‐1‐1 Higashi, Tsukuba, Ibaraki 305‐8562 (Japan);5. Graduate School of Science and Engineering, Yamagata University, 1‐1‐1 Higashi, Tsukuba, Ibaraki 305‐8562 (Japan) |
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Abstract: | Supramolecular rosettes of oligothiophenes that do not bear long aliphatic tails have been designed as semiconducting nanomaterials for solution‐processable bulk heterojunction solar cells. The rosettes consist of six barbiturated thienyloligo(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. |
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Keywords: | nanostructures oligothiophene photovoltaics self‐assembly supramolecular chemistry |
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