Thermally, Operationally, and Environmentally Stable Organic Thin-Film Transistors Based on Bis[1]benzothieno[2,3-d:2′,3′-d′]naphtho[2,3-b:6,7-b′]dithiophene Derivatives: Effective Synthesis, Electronic Structures, and Structure-Property Relationship

By developing an efficient synthetic route to the bis[1]benzothieno[2,3-d;2',3'-d]naphtho[2,3-b;6,7-b']dithiophene (BBTNDT) framework, we have successfully synthesized new BBTNDT derivatives with phenyl (DPh-BBTNDT) or n-hexyl groups (C6-BBTNDT) at the 2 and 10 positions. Characterization of their vapor-deposited thin films revealed that, depending on the substituents introduced, their HOMO energy levels were slightly altered, and DPh-BBTNDT with the HOMO energy level of ca. 5.3 eV was supposed to be a stable organic semiconductor under ambient conditions. In fact, the DPh-BBTNDT-based OTFTs showed not only high mobility of up to 7.0 cm(2) V-1 s(-1) under ambient conditions but also excellent operational and thermal stabilities up to 300 degrees C, whereas the parent and the hexyl derivative were less stable against the thermal treatments at high temperatures. The high mobility observed for the DPh-BBTNDT-based OTFTs can be correlated to the interactive packing structure in the bulk single crystal and thin film state of DPh-BBTNDT, which corroborates the existence of the well-balanced two-dimensional electronic structure in the solid state. With these excellent device characteristics, it can be concluded that DPh-BBTNDT is a promising and practical vapor-processable organic semiconductor, which can afford thermally, operationally, and environmentally stable OTFTs as well as high mobility.