Boosting Carrier Mobility in Novel Naphthodithiophene Diimide (NDTI)‐Based Triad Through π‐Conjugation Expansion

Abstract Enhancing the length of π‐conjugation in molecules represents an efficient strategy for fine‐tuning the optoelectronic characteristics of organic semiconductors. Nevertheless, this approach is infrequently conducted for small molecules with n‐type properties. Herein, we report the design and synthesis of a novel naphthodithiophene diimide (NDTI)‐based small‐molecule semiconductor, NDTI‐BBTE , featuring a long benzo[b]thiophen‐2‐ylethynyl (BTE) end cap. NDTI‐BBTE exhibits good solubility in some common organic solvents and a LUMO energy level of −4.15 eV, promoting stable electron transport in ambient conditions. Compared to our previously reported NDTI‐BET with a thiophenylethynyl end cap, NDTI‐BBTE shows improved device performance, achieving a maximum electron mobility of 0.052 cm 2 V⁻¹ s⁻¹ under identical conditions. The XRD and AFM measurements reveal that NDTI‐BBTE has lower d ‐spacing and higher crystallinity than NDTI‐BTE . These results demonstrate that increasing π‐conjugation length of the molecules is a simple and effective strategy for designing solution‐processable, air‐stable n‐type organic semiconductors for printed electronics.