title: Air-stable n-type organic field-effect transistors based on solution-processable, electronegative oligomers containing dicyanomethylene-substituted cyclopenta[b]thiophene.
abstract: Solution-processable, electronegative, π-conjugated systems containing dicyanomethylene-substituted cyclopenta[b]thiophene were synthesized as potential active materials for air-stable n-type organic field-effect transistors (OFETs). Electrochemical measurements revealed that these compounds exhibited electrochemical stability and that the lowest unoccupied molecular orbital (LUMO) had an energy level less than -4.0 eV. Flash-photolysis time-resolved microwave conductivity (FP-TRMC) measurements were performed, and the value of intradomain electron mobility was determined to be as high as 0.1 cm(2) V(-1) s(-1) . The OFETs were fabricated by spin-coating thin films of the compounds as an active layer. The electron mobility of the OFETs was 3.5×10(-3) cm(2) V(-1) s(-1) in vacuum. Furthermore, electron mobility of the same order of magnitude and stable characteristics were obtained under air-exposed conditions. X-ray diffraction measurements of the spin-coated thin films revealed the difference of molecular arrangements depending on the inner conjugated units. Atomic force microscopy measurements of crystalline-structured films exhibited the formation of grains. The accomplishment of air-stability was attributed to the combined effect of the low-lying LUMO energy level and the molecular arrangements in the solid state, avoiding both the quenching of electron carriers and the intrusion of oxygen and/or moisture.
authors: The Institute of Scientific and Industrial Research, Osaka University, 8-1, Mihogaoka, Ibaraki, Osaka 567-0047, Japan. yutakaie@sanken.osaka-u.ac.jp
authors: Yutaka
authors: Y
authors: Ie
authors: Kazufumi
authors: K
authors: Nishida
authors: Makoto
authors: M
authors: Karakawa
authors: Hirokazu
authors: H
authors: Tada
authors: Atsushi
authors: A
authors: Asano
authors: Akinori
authors: A
authors: Saeki
authors: Shu
authors: S
authors: Seki
authors: Yoshio
authors: Y
authors: Aso