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Organic Semiconducting Materials from Sulfur-Hetero Benzo[k]fluoranthene Derivatives: Synthesis, Photophysical Properties, and Thin Film Transistor Fabrication

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journal contribution
posted on 18.07.2008, 00:00 by Qifan Yan, Yan Zhou, Ben-Bo Ni, Yuguo Ma, Jian Wang, Jian Pei, Yong Cao
A new family of air-stable sulfur-hetero oligoarenes based on the benzo[k]fluoranthene unit has been facilely developed as the active materials for thin film organic field-effect transistors. The Diels−Alder reaction between cyclopentadienone 1 and 2,2′-(ethyne-1,2-diyl)bisthiophene followed by decarbonylation afforded fluoranthene derivative 2. After bromination and subsequent substitution through Suzuki coupling reaction, the FeCl3-oxidative cyclization produced sulfur-hetero benzo[k]fluoranthene derivatives 812. In dilute chloroform solution, the absorption and emission behaviors of 2 and 47 showed characteristic features of the fluoranthene units, while their emission λmax red-shifted with an increase of the effective conjugation length. The steady state absorption and emission spectra of these newly synthesized compounds were thoroughly investigated and discussed. Thin film organic field-effect transistors (OFETs) using 811 as active materials were fabricated in a “top contact” configuration. Substituents at the skeleton play an important role in the film morphologies, which lead to different mobilities, while the charge mobilities of 811 from OFETs were improved after thermal annealing of the thin films. A carrier mobility as high as 0.083 cm2 V−1 s−1 and current on/off ratio of 106 were achieved through vacuum-deposited film followed by the thermal annealing process from 11.