Synthesis and physical properties of brominated hexacene and hole-transfer properties of thin-film transistors

Motonori Watanabe; Takaaki Miyazaki; Toshinori Matsushima; Junko Matsuda; Ching-Ting Chein; Masahiko Shibahara; Chihaya Adachi; Shih-Sheng Sun; Tahsin J Chow; Tatsumi Ishihara

doi:10.1039/c7ra13632c

Synthesis and physical properties of brominated hexacene and hole-transfer properties of thin-film transistors

RSC Adv. 2018 Apr 10;8(24):13259-13265. doi: 10.1039/c7ra13632c. eCollection 2018 Apr 9.

Authors

Motonori Watanabe¹, Takaaki Miyazaki², Toshinori Matsushima^{1

3

4}, Junko Matsuda¹, Ching-Ting Chein⁵, Masahiko Shibahara⁶, Chihaya Adachi^{1

2

3

4

7}, Shih-Sheng Sun⁵, Tahsin J Chow^{5

8}, Tatsumi Ishihara^{1

7}

Affiliations

¹ International Institute for Carbon Neutral Energy Research, Kyushu University 744 Motooka, Nishi-ku, Fukuoka 819-0395 Japan mwata@i2cner.kyushu-u.ac.jp.
² Education Center for Global Leaders in Molecular Systems for Devices, Kyushu University 744 Motooka Nishi-ku Fukuoka 819-0395 Japan.
³ Center for Organic Photonics and Electronics Research (OPERA), Kyushu University 744 Motooka, Nishi-ku Fukuoka Japan.
⁴ Japan Science and Technology Agency (JST), ERATO, Adachi Molecular Exciton Engineering Project 744 Motooka, Nishi-ku Fukuoka 819-0395 Japan.
⁵ Institute of Chemistry, Academia Sinica No. 128, Academia Road Sec 2, Nankang Taipei 11529 Taiwan.
⁶ Division of Natural Sciences, Faculty of Science and Technology, Oita University Dannoharu 700 Oita Japan.
⁷ Department of Applied Chemistry, Faculty of Engineering, Kyushu University Nishi-ku Fukuoka 819-0395 Japan.
⁸ Department of Chemistry, Tunghai University Taichung 40704 Taiwan.

Abstract

A halide-substituted higher acene, 2-bromohexacene, and its precursor with a carbonyl bridge moiety were synthesized. The precursor was synthesized through 7 steps in a total yield of 2.5%. The structure of precursor and thermally converted 2-bromohexacene were characterized by solid state NMR, IR, and absorption spectra, as well as by DFT computation analysis. It exhibited high stability in the solid state over 3 months, therefore can be utilized in the fabrication of opto-electronic devices. The organic thin-film transistors (OFETs) were fabricated by using 2-bromohexacene and parent hexacene through vaccum deposition method. The best film mobility of 2-bromohexacene was observed at 0.83 cm² V^-1 s^-1 with an on/off ratio of 5.0 × 10⁴ and a threshold of -52 V, while the best film mobility of hexacene was observed at 0.076 cm² V^-1 s^-1 with an on/off ratio of 2.4 × 10² and a threshold of -21 V. AFM measurement of 2-bromohexacene showed smooth film formation. The averaged mobility of 2-bromohexacene is 8 fold higher than the non-substituted hexacene.