Fused phthalimide-based A–DA′D–A small molecule: New protocol for n-type organic semiconductors

Abstract

Development of well-conjugated building blocks by a concise and efficient synthetic procedure is crucial for organic electronics. In particular, for A–DA′D–A-type (A = donor and D = acceptor) organic semiconductors, which are the most popular and successful small molecular acceptors, the limited number DA′D fused cores limits the variety of these molecules. Herein, we report a new A–DA′D–A-type small molecule, TIIC, containing an entirely new DA′D fused core. The complete synthetic procedure, including a well-designed photocyclization step, resulted in above 50% total yield over five steps. TIIC shows strong light absorption in the complete visible region because of the extended π-conjugation and strong intramolecular charge transfer. The deep lowest unoccupied molecular orbital energy level (−4.0 eV) of TIIC, which indicates the n-type semiconductor property, was further confirmed by the organic field-effect transistor performance with unipolar electron mobility of 3.51 × 10−4 cm2 V−1 s−1.