Chasing the "killer" phonon mode for the rational design of low disorder, high mobility molecular semiconductors

Guillaume Schweicher, Gabriele D'Avino, Michael T. Ruggiero, David J. Harkin, Katharina Broch, Deepak Venkateshvaran, Guoming Liu, Audrey Richard, Christian Ruzié, Jeff Armstrong, Alan R. Kennedy, Kenneth Shankland, Kazuo Takimiya, Yves H. Geerts, J. Axel Zeitler, Simone Fratini, Henning Sirringhaus

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Molecular vibrations play a critical role in the charge transport properties of weakly van der Waals bonded organic semiconductors. To understand which specific phonon modes contribute most strongly to the electron – phonon coupling and ensuing thermal energetic disorder in some of the most widely studied high mobility molecular semiconductors, we have combined state-of-the-art quantum mechanical simulations of the vibrational modes and the ensuing electron phonon coupling constants with experimental measurements of the lowfrequency vibrations using inelastic neutron scattering and terahertz time-domain spectroscopy. In this way we have been able to identify the long-axis sliding motion as a 'killer' phonon mode, which in some molecules contributes more than 80% to the total thermal disorder. Based on this insight, we propose a way to rationalize mobility trends between different materials and derive important molecular design guidelines for new high mobility molecular semiconductors.
Original languageEnglish
Article number1902407
Number of pages11
JournalAdvanced Materials
Issue number43
Early online date12 Sep 2019
Publication statusPublished - 25 Oct 2019


  • electron-photon coupling
  • molecular vibrations
  • organic semiconductors

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