Impacts of alkyl side chain length on film formation and charge transport in π-extended anthradithiophenes

Thienoacenes, particularly anthradithiophene (ADT), have emerged as promising semiconductor materials for organic field-effect transistors (OFETs). ADT, an isoelectronic analogue of pentacene, features an extended π-system with an anthracene core connected to two thiophene rings. To enhance the solubility and stability of solution-processed ADT thin films, alkyl or alkylphenylethynyl side chain substitutions have been proposed. However, the limited understanding of how these side chain modifications influence the optical and electrical properties of ADT derivatives hinders the rational design of high-performance OFETs. To address this challenge, we synthesized a series of ADT derivatives substituted with alkylphenylethynyl groups (C_n-PEADT, n = 4, 6, 8, and 10) and systematically studied the effects of varying side chain lengths on crystal structure, optical properties, and electrical performance. Our findings offer valuable insights into the relationship between side chain modifications and the microstructure and performance of these semiconducting materials, contributing to the advancement of organic electronic devices.