Solution-processable n-type organic field-effect transistor (OFET) materials based on carbonyl-bridged bithiazole and dioxocyclopentene-annelated thiophenes.

A series of electronegative π-conjugated compounds composed of carbonyl-bridged bithiazole and alkyl-substituted dioxocyclopenta[b]thiophene were synthesized as a candidate for solution-processable n-type organic semiconductor materials and characterized on the basis of photophysical and electrochemical properties. Cyclic voltammetry measurements showed that the first half-wave reduction potentials of these compounds are between -0.97 and -1.14 V versus ferrocene/ferrocenium, which corresponds to lowest unoccupied molecular orbital energy levels between -3.83 and -3.66 eV. Thanks to hexyl or dodecyl groups in the molecules, the compounds are sufficiently soluble to realize the fabrication of their thin films through a spin-coating method. As a result, the prepared organic field-effect transistors based on these newly developed compounds exhibited n-channel characteristics not only under vacuum but also in air, and the best field-effect electron mobility observed under vacuum was 0.011 cm(2) V(-1) s(-1) with an on/off ratio of 10(8) and a threshold voltage of 16 V.