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Air‐Stable n‐Type Organic Field‐Effect Transistors Based on Solution‐Processable, Electronegative Oligomers Containing Dicyanomethylene‐Substituted Cyclopenta[ b ]thiophene
Author(s) -
Ie Yutaka,
Nishida Kazufumi,
Karakawa Makoto,
Tada Hirokazu,
Asano Atsushi,
Saeki Akinori,
Seki Shu,
Aso Yoshio
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002995
Subject(s) - homo/lumo , thiophene , electron mobility , materials science , conjugated system , spin coating , flash photolysis , organic electronics , pedot:pss , organic semiconductor , chemistry , thin film , photochemistry , layer (electronics) , polymer , transistor , optoelectronics , molecule , organic chemistry , nanotechnology , physics , quantum mechanics , voltage , reaction rate constant , kinetics
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.