Herein, we propose a new strategy to develop air-stable n-type organic semiconductors with non-classical thiophene aromatic diimide derivatives by replacing aromatic naphthalene with a heteroaromatic isothianaphthene core. We designed and successfully synthesized the isothianaphthene core based diimide material, N,N′-bis(n-hexyl)isothianaphthene-2,3,6,7-tetra-carboxylic acid diimide (BTDI-C6) as an n-type semiconductor. Compared to N,N′-bis(n-hexyl)naphthalene-1,4,5,8-tetracarboxylic acid diimide (NDI-C6), BTDI-C6 possesses a deeper LUMO energy level of −4.21 eV, which is 0.32 eV lower than that of NDI-C6. Both molecular modelling and experimental results elucidated that organic thin film transistors (OTFTs) based on both of these materials exhibit comparable mobilities; however, the threshold voltage of BTDI-C6 based device (+7.5 V) is significantly lower than that of NDI-C6 based counterpart (+34 V). Moreover, the low-lying LUMO energy level of BTDI-C6 ensures excellent air-stability which is further validated by the device performance. In addition, BTDI-C6 shows high luminescence while NDI-C6 is not luminescent at all in solution, which reveals the potential application of our newly synthesized material in n-type light-emitting transistors.
isothianaphthene non-classical imide n-type
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This work was supported by Shenzhen Science and Technology (JCYJ20170412151139619), Shenzhen Engineering Laboratory (Shenzhen development and reform commission 1592), Guangdong Key Research Project (2019B010924003), Guangdong International Science Collaboration Base (2019A050505003), and Shenzhen Peacock Plan (KQTD2014062714543296).