Effects of oligothiophene π-bridge length on physical and photovoltaic properties of star-shaped molecules for bulk heterojunction solar cells

Jie Min*, Yuriy N. Luponosov, Derya Baran, Sergei N. Chvalun, Maxim A. Shcherbina, Artem V. Bakirov, Petr V. Dmitryakov, Svetlana M. Peregudova, Nina Kausch-Busies, Sergei A. Ponomarenko, Tayebeh Ameri, Christoph J. Brabec

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

The preparation of four different star-shaped donor (D)-π-acceptor (A) small molecules (N(Ph-1T-DCN-Me) 3 , N(Ph-2T-DCN-Me) 3 , N(Ph-2T-DCN-Hex) 3 and N(Ph-3T-DCN-Hex) 3 ) possessing various oligothiophene π-bridge lengths and their use in solution-processed bulk heterojunction small molecule solar cells is reported. Optical and electrochemical data show that increasing oligothiophene π-bridge length leads to a decrease of the optical band gap due to a parallel increase of the highest occupied molecular orbital (HOMO) level. Furthermore, subtle modifications of a molecular π-bridge length strongly affect the thermal behavior, solubility, crystallization, film morphology and charge carrier mobility, which in turn significantly change the device performance. Although the moderately increasing oligothiophene π-bridge length uplifts the HOMO level, it nevertheless induces an increase of the efficiency of the resulting solar cells due to a simultaneous improvement of the short circuit current (J sc ) and fill factor (FF). The study demonstrates that such an approach can represent an interesting tool for the effective modulation of the photovoltaic properties of the organic solar cells (OSCs) at a moderate cost.

Original languageEnglish (US)
Pages (from-to)16135-16147
Number of pages13
JournalJournal of Materials Chemistry A
Volume2
Issue number38
DOIs
StatePublished - Oct 14 2014

ASJC Scopus subject areas

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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