• Gann, Eliot
• Maniam, Subashani
• Langford, Steven J.
• Welford, Adam
• Thomsen, Lars

Abstract

<p>The replacement of the imide oxygen atoms with sulfur atoms in the naphthalene diimide (NDI) framework is an attractive strategy for tuning of the electronic properties of such molecules. Here we report the synthesis and characterization of the full series of six thionated NDI molecules with branched side chains. In order to provide a direct comparison with the unthionated parent molecule, a top-gate, bottom contact geometry is adopted, with work function-modified gold electrodes facilitating electron injection. The highest electron mobility was observed for the S2-cis molecule, with a mobility of 0.20 cm²/Vs compared to 0.068 cm²/Vs for the parent molecule. Mobilities slightly lower than that achieved for the S2-cis molecule were also achieved for the S2-trans and S3 derivatives, with the S1, S4 and S2-cis imide derivatives showing mobilities lower than the parent molecule. The thin film microstructure of these molecules has also been explored using a combination of grazing-incidence wide-angle X-ray scattering and near-edge X-ray absorption fine-structure spectroscopy. The performance and microstructure of thin films deposited either by spin-coating or blade coating are also compared. • Synthesis and OFET performance of the full set of 6 thionated NDI derivatives reported.• A top-gate geometry and blade-coating yields higher electron mobilities than previously reported.• An electron mobility of 0.20 cm²/Vs achieved for the S2-cis molecule.• Highly ordered microstructures achieved with blade-coating with molecular terracing evident.• Thin film microstructure evaluated with synchrotron-based techniques.</p>

Topics

• impedance spectroscopy
• microstructure
• mobility
• thin film
• Oxygen
• gold
• wide-angle X-ray scattering
• chemical ionisation