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Issue 13, 2015
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Effect of side chain length on film structure and electron mobility of core-unsubstituted pyromellitic diimides and enhanced mobility of the dibrominated core using the optimized side chain

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Abstract

Pyromellitic diimides (PyDIs) are π-conjugated electron-transport materials based on an unusually small aromatic core (benzene), which provides low temperature processing and transparency in much of the visible range. We synthesized PyDI derivatives with a systematic series of fluoroalkyl side chains and investigated their film structures and electrical performances in thin-film transistors. The effect of the length of the fluorinated segment in fluoroalkylmethylene side chains was examined. Shorter side chains within this series induce higher electron mobilities, with a maximum of 0.026 cm2 V−1 s−1 achieved with the perfluorobutylmethyl side chain. Atomic force microscopy images and X-ray diffraction peak widths were used as indications of crystallinity correlating with the mobility trend. The perfluorobutylmethyl side chain, when attached to 3,6-dibromo PyDI using a total of three synthetic steps, allowed nearly parallel PyDI cores and an exceptional mobility of 0.2 cm2 V−1 s−1, accompanied by a correspondingly excellent morphology and effective intermolecular packing illustrated by a single crystal X-ray structure. This is the highest PyDI mobility yet reported, and is an unusually high mobility for a compound with such a small core, having such low visible range absorbance, and requiring so few synthetic steps.

Graphical abstract: Effect of side chain length on film structure and electron mobility of core-unsubstituted pyromellitic diimides and enhanced mobility of the dibrominated core using the optimized side chain

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Supplementary files

Article information


Submitted
15 Nov 2014
Accepted
04 Feb 2015
First published
06 Feb 2015

J. Mater. Chem. C, 2015,3, 3029-3037
Article type
Paper

Effect of side chain length on film structure and electron mobility of core-unsubstituted pyromellitic diimides and enhanced mobility of the dibrominated core using the optimized side chain

M. Yeh, S. Wang, J. F. Martínez Hardigree, V. Podzorov and H. E. Katz, J. Mater. Chem. C, 2015, 3, 3029
DOI: 10.1039/C4TC02611J

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