Synthesis and photovoltaic effect in red/near-infrared absorbing A-D-A-D-A-type oligothiophenes containing benzothiadiazole and thienothiadiazole central units

Yuriy N. Luponosov, Jie Min*, Dmitry A. Khanin, Derya Baran, Sergey A. Pisarev, Svetlana M. Peregudova, Petr V. Dmitryakov, Sergei N. Chvalun, Georgiy V. Cherkaev, Evgeniya A. Svidchenko, Tayebeh Ameri, Christoph J. Brabec, Sergei A. Ponomarenko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

8 Scopus citations

Abstract

Two π-conjugated acceptor-donor-acceptor-donor-acceptor-type (A-D-A-D-A) oligothiophenes, TT-(2T-DCV-Hex)2 and BT-(2T-DCV-Hex)2 were designed and synthesized with thienothiadiazole (TT) or benzothiadiazole (BT) as the core and dicyanovinyl (DCV) as the terminal acceptor groups for comprehensively investigating and understanding structure-property relationships. The resulting oligomers were first characterized by thermal analysis, UV-Vis spectroscopy, and cyclic voltammetry. By simply changing the BT to TT core in these two oligothiophenes, the highest occupied molecular orbital levels were varied from-5.55 eV for BT-(2T-DCV-Hex)2 to-5.11 eV for TT-(2T-DCV-Hex)2, and the optical band gaps were varied from 1.72 eV for BT-(2T-DCV-Hex)2 to 1.25 eV for TT-(2T-DCV-Hex)2, ascribed to the stronger electron accepting character of the TT core. However, the power conversion efficiency of bulk heterojunction organic solar cells (OSCs) with TT-(2T-DCV-Hex)2 as donor and [6,6]-phenyl C70-butyric acid methyl ester (PC71BM) as acceptor was measured to be 0.04% only, which is much lower than that of BT-(2T-DCV-Hex)2:PC71BM (1.54%). Compared to the TT-(2T-DCV-Hex)2 system, the BT-(2T-DCV-Hex)2 based device shows smoother film surface morphology, and superior charge generation and charge carrier mobilities. Therefore, the results clearly demonstrate that in addition to modifying the alkyl side chains and p-bridge lengths, the design of new small molecules for high-performance OSCs should also aim to choose suitable acceptor units.

Original languageEnglish (US)
JournalJournal of Photonics for Energy
Volume5
Issue number1
DOIs
StatePublished - Jan 1 2015
Externally publishedYes

Keywords

  • benzothiadiazole
  • charge carrier mobility
  • charge generation
  • dicyanovinyl group
  • Donor-acceptor oligomer
  • organic solar cell
  • thienothiadiazole

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Renewable Energy, Sustainability and the Environment

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