Synthesis and characterization of anthra[2,3-b]thiophene and tetraceno[2,3-b]thiophenes for organic field-effect transistor applications

A series of thiophene-fused acenes, anthra[2,3-b]thiophene (1), tetraceno[2,3-b]thiophene (2), and 2-n-decyl-tetraceno[2,3-b]thiophene (3), were synthesized. The crystal structures of 1 and 2 were determined. A weak dipole results from the addition of the thiophene ring, and the crystal packing changes from the triclinic structure of acenes to orthorhombic, with the molecules maintaining the herringbon e arrangement with the molecular long axis antiparallel to the neighbors. Theoretical calculation showed that the molecules have higher oxidation potential and comparable hole mobility as acene analogues with the same number of rings. Thin film transistor devices were fabricated from these materials. With compound 1, a field-effect mobility of 0. 134 cm(2)/V s and on/off ratio of 10(8) can be achieved when deposited at a substrate temperature of 25 degrees C, whereas a mobility of 0.245 cm(2)/V s and on/off ratio of 106 were observed for compound 2 deposited at 80 degrees C.