Manipulating Molecular Stacking to Achieve High Electron Mobility in 2D Conjugated Ultra‐Narrow Bandgap Non‐Fullerene Acceptors with Absorption Beyond 1000 nm

Abstract N‐type organic semiconductors are essential for the advancement of organic electronic devices. However, in relation to extensive research on n‐type and p‐type polymers, studies on high‐mobility n‐type small‐molecule semiconductors (SMSCs) are limited. Here, a series of ultra‐narrow bandgap n‐type SMSCs are developed on an A‐D‐A‐type structure. These SMSCs feature an exceptionally large π‐conjugated area, leading to strong intramolecular charge transfer and robust π‐π interactions. For the first time, central core and terminal halogenation are employed to control molecular surface electrostatic potential distribution, thereby regulating the π‐π stacking area (S_π‐π) and studying their correlation. The research reveals that, in n‐type SMSCs with an edge‐on arrangement, introducing fluorine into the 2D central core can reduce the S_π‐π, which is detrimental to the electron mobility (µ_e) of organic field‐effect transistors (OFETs). Conversely, terminal chlorination facilitates electron injection and improves µ_e. Consequently, DTPC‐OD‐4Cl, featuring shorter alkyl side chains and a non‐fluorinated 2D central core and undergoing terminal chlorination, achieved the highest µ_e of up to 0.52 cm² V⁻¹ s⁻¹, ranking among the highest values reported for A‐D‐A type SMSCs. This work not only systematically investigated the influence of molecular structure on mobility but also provided novel insights for designing more efficient n‐type SMSCs.