Intramolecular Locked Dithioalkylbithiophene-Based Semiconductors for High-Performance Organic Field-Effect Transistors

New 3,3′-dithioalkyl-2,2′-bithiophene (SBT)-based small molecular and polymeric semiconductors are synthesized by end-capping or copolymerization with dithienothiophen-2-yl units. Single-crystal, molecular orbital computations, and optical/electrochemical data indicate that the SBT core is completely planar, likely via S(alkyl)⋯S(thiophene) intramolecular locks. Therefore, compared to semiconductors based on the conventional 3,3′-dialkyl-2,2′-bithiophene, the resulting SBT systems are planar (torsional angle <1°) and highly π-conjugated. Charge transport is investigated for solution-sheared films in field-effect transistors demonstrating that SBT can enable good semiconducting materials with hole mobilities ranging from ≈0.03 to 1.7 cm² V⁻¹ s⁻¹. Transport difference within this family is rationalized by film morphology, as accessed by grazing incidence X-ray diffraction experiments.