Bis[1]benzothieno[5,4-d:5′,4′-d′]benzo[1,2-b:4,5-b′]dithiophene Derivatives: Synthesis and Effect of Sulfur Positions on Their Transistor Properties

Bis[1]benzothieno[5,4-d:5',4']benzo[1,2-b:4,5-b']dithiophene, 2-b phene (BBTBDT-2) and its phenyl-substituted derivative were successfully synthesized and characterized. From DFT calculations, highest occupied molecular orbitals (HOMOs) of both compounds are well delocalized and large orbital coefficients exist on sulfur atoms. Single-crystal X-ray analysis revealed that BBTBDT-2 derivatives formed herringbone structures in the solid state. In particular, BBTBDT-2 formed a layer-bylayer structure with effective 2D charge-carrier transporting capability. The fabricated OFETs based on BBTBDT-2 gave mobility up to 0.49 cm(2)V(-1)s(-1) in the vacuum-deposited thin films, which is the highest value among BBTBDT derivatives including our previously reported syn-counterparts. We have also clarified a detailed structure-property relationship of sulfur positions and phenyl substituents as indicated by theoretical calculation, GIWAXS, and AFM analyses.