Abstract
Development of organic semiconducting materials based on π-conjugated systems for use in organic field-effect transistors (OFETs) has become an active area of research. We have designed and synthesized a series of electronegative units: Carbonyl-bridged bithiazole, dialkyl-substituted naphtho[2,3-c]thiophene-4,9-dione, alkyl-substituted dioxocyclopenta[b]thiophene, and dicyanomethylene-substituted cyclopenta[b]thiophene. The electronegative π-conjugated systems containing these units have been synthesized as potential active materials for air-stable and/or solution-processable n-type OFETs. Electrochemical measurements revealed that the annelation of the electron-withdrawing group contributes both to lowering the lowest unoccupied molecular orbital energy level and to stabilizing the formation of anionic species. Some of compounds are sufficiently soluble to realize the fabrication of their thin films through a solution technique. These electronegative compounds exhibited n-type semiconducting behavior not only in vacuum but also under air-exposed conditions.
