In recent years, organic thin film transistors (OTFTs) are attracting ever increasing attention due to their great potentials in thin/lightweight, flexible, and fashionable electronic product. Driven by the demand for low-cost, large-area, and flexible organic electronic devices, organic complementary circuits comprising both p- and n-channel OTFTs are very important due to their low power dissipation, high operating speed, and good noise margin. Now, the performance of n-type organic semiconductors is far outmatched by that of more intensively investigated p-type materials. The lack of high-performance, ambient-stable n-channel OTFTs, especially those that can be solution-processed in terms of low-cost/large-area virtues, has hindered the development of organic complementary circuits.

　  The researchers (at Shanghai Institute of Organic Chemistry, CAS) and their co-workers (at Institute of Chemistry, CAS) reported on a new class of n-type organic semiconductors based on core-expanded naphthalene diimides fused with 2-(1,3-dithiol-2-ylidene)malonitrile groups (see Figure 1). The first two representatives of these species, derived from long branched N-alkyl chains have been used successfully as active layers for solution-processed n-channel OTFTs. The fabricated devices exhibit high electron mobilities of up to 0.51 cm²V^-1s^-1, with current on/off ratios ratios of 10⁵−10⁷, and threshold voltages below 10 V under ambient conditions. Moreover, their excellent air and operating stability warrant their great potential in organic electronics (see Figure 2). The related work has been applied for a CN patent, some results of which were published in J. Am. Chem. Soc. 2010, 132, 3697-3699.