Small-molecule semiconductors containing dithienylacrylonitrile for high-performance organic field-effect transistors

Abstract

We designed and synthesized four donor–acceptor-type conjugated small-molecule compounds DPP-CN-DTE-1, DPP-CN-DTE-2, DPP-DTE-CN-1 and DPP-DTE-CN-2. The four compounds contained long alkyl side chains on the diketopyrrolopyrrole acceptor unit and cyano (CN) groups substituted on the dithiophene ethylene donor unit at different positions. The four small molecules exhibited good thermal stability and solution dispersibility. The bottom gate-bottom contact OFET devices based on these compounds showed excellent p-type performances. The relationship between molecular structures and field-effect performances indicated that the alkyl side-chain length and the CN substituted position significantly affected their charge carrier transport properties. The DPP-CN-DTE-1 with side-chain 2-mercaptotetradecyl side-chains and inner-side substituted CN groups exhibited the highest hole mobility of 2.52 cm² V⁻¹ s⁻¹. This work provided a promising approach to develop excellent p-type small-molecule semiconductors with high performance, good solution processability and thermal stability for device fabrications.