The effect of side-chain length on the microstructure and processing window of zone-cast naphthalene-based bispentalenes

Katelyn P. Goetz, Kohei Sekine, Fabian Paulus, Yu Zhong, Daniel Roth, David Becker-Koch, Yvonne J. Hofstetter, Elena Michel, Lisa Reichert, Frank Rominger, Matthias Rudolph, Sven Huettner, Yana Vaynzof, Eva M. Herzig, A. Stephen K. Hashmi, Jana Zaumseil

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Abstract

The solubilizing side-groups of solution-processable π-conjugated organic semiconductors affect both the crystal structure and microstructure of the respective thin films and thus charge-carrier mobility in devices. In this work, we explore how the alkyl side-chain length influences thin-film structure and charge transport in field-effect transistors of zone-cast, naphthalene-based bispentalenes. By tuning the alkyl-chain length and the casting speed, we alter the microstructure from highly aligned ribbons, to feathered ribbons, to disordered grains. Concurrently, the hole mobility changes over two orders of magnitude, from 0.001 cm2 V-1 s-1 at the fastest speeds to roughly 0.1 cm2 V-1 s-1 at slower speeds. The highest mobilities correspond to the presence of an aligned ribbon morphology. While optical measurements indicate negligible electronic differences between the molecules, grazing incidence X-ray diffraction measurements show that the films display different degrees of order and alignment. The compound with pentyl side-chains exhibits the largest tolerance to different processing conditions, yielding an aligned ribbon microstructure and high mobility over a wide range of casting speeds. Our results highlight the impact that even small changes to the molecular structure can have on the processing window and transport properties of thin-film devices.

Original languageEnglish
Pages (from-to)13493-13501
Number of pages9
JournalJournal of Materials Chemistry C
Volume7
Issue number43
DOIs
Publication statusPublished - Jan 1 2019
Externally publishedYes

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All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Chemistry

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