Fused π-conjugated molecules have been extensively developed as critical and indispensable components in organic semiconductors due to their desirable physicochemical properties and charge-transport characteristics. Incorporation of acceptor units into fused π-conjugated frameworks has advantages in terms of tuning frontier molecular orbital energies. However, development of fused π-conjugated molecules with donor-acceptor configurations is still lacking due to limited availability and synthetic access to acceptor units. Here, we report the design and synthesis of a new fused donor-acceptor-donor π-conjugated molecule (BDT-NTz) composed of electron-donating benzodithiophene (BDT) units and an electron-accepting naphthobisthiadiazole (NTz) unit. The fused chemical structure of BDT-NTz generated a sharp absorption band and a high quantum efficiency. This indicated that BDT-NTz showed typical p-type responses with a hole mobility of 1.1 × 10−3 cm2 V−1 s−1 in an organic field-effect transistor. We also developed a copolymer based on BDT-NTz and an electron-accepting fluorinated NTz and investigated its photophysical/electrochemical properties and semiconducting characteristics. This study demonstrates that the use of fused π-extended molecules containing NTz can broaden the availability of both small-molecule-based and polymer-based organic semiconducting materials.
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This work was supported by JSPS KAKENHI (20H02814, 20H05841, 20KK0123, 19K15505, 20H04639, and 21K14602), CREST (J205101030), NEDO (21500248-0), and “Dynamic Alliance for Open Innovation Bridging Human, Environmental and Materials” from the Ministry of Education, Culture, Sports, Science and Technology, Japan. YI is grateful to the Takahashi Industrial and Economic Research Foundation and NAGASE Science Technology Foundation. Thanks are extended to the CAC, ISIR, for assistance in obtaining elemental analyses. We appreciate Prof. Dr. Kenji Matsuda (Kyoto University) and Dr. Daiki Shimizu (Kyoto University) for the measurement of fluorescence lifetime and absolute quantum yield. We also wish to express our appreciation to Prof. Dr. Akinori Saeki (Osaka University) for the PYS measurements.
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Asakawa, R., Seo, T., Yokoyama, S. et al. A fused π-extended molecule containing an electron-accepting naphthobisthiadiazole and its incorporation into a copolymer: synthesis, properties, and semiconducting performance. Polym J 55, 451–461 (2023). https://doi.org/10.1038/s41428-022-00716-x