U-Shaped Heteroacenes Embedded with Heavy Chalcogen Atoms: Unique Bilayer Self-Organization of Crooked π-Cores Enabling Efficient Charge Transport

Organic semiconductors are indispensable functional materials for next-generation printed electronics, and significant progress has been made in the development of high-mobility organic semiconductors in recent years. Most of these molecules rely on the use of linearly π-extended polycyclic heteroaromatic systems, referred to as heteroacenes, as the functional core. Here, to expand the scope of the rational design of organic semiconductors, a new series of U-shaped heteroacenes that features unprecedented “U” geometric configuration together with systematic chalcogen modification is elaborated. This U-shaped molecular geometry promotes the formation of supramolecular bilayer lamellar assemblies, in which the U-shaped molecules are packed into a head-to-head arrangement via the multiple intermolecular chalcogen interactions. Importantly, the incorporation of heavier chalcogen atoms (selenium and tellurium) instead of sulfur atoms can systematically modulate the key electronic properties of materials by influencing the molecular geometry, frontier orbital energy levels, and noncovalent intermolecular interactions. Consequently, anisotropic, high hole mobilities of up to 3.8 cm² V⁻¹ s⁻¹ can be attained in thin-film organic field-effect transistors based on the selenium-embedded U-shaped heteroacene. In this study, the relationship between the molecular structures, supramolecular self-organization, and charge transport properties among these U-shaped heteroacenes are investigated from computational and experimental perspectives.