Molecular design of organic semiconductors for high performance organic field-effect transistors

Abstract

Much attention has been focused on organic field-effect transistors (OFET)s from view point of application purposes for electronic devices as well as basic interest in charge transportation. Development of new semiconductors showing high-performance FET characteristics is particularly important to make progress in this field. For this purpose, we have designed various kinds of heterocyclic compounds with electron-donating or accepting properties. We have used tetrathiafulvalene (TTF) derivatives as semiconductors. High hole mobilities were achived by introducing naphthalene (0.42 cm2/Vs) or quinoxaline (0.20 cm2/Vs) rings to the TTF unit. Furthermore, we have introduced electron-withdrawing halogen groups into the quinoxaline group and found that the derivatives showed high performance n-type behavior. We have also developed high performance n-type FETs by introducing trifluoromethylphenyl groups in heterocyclic π-electron systems. The bithiazole and thiazolothiazole derivatives showed high electron mobilites over 1 cm2/Vs. Decrease of the threshold values was accomplished by introducing strong electron-withdrawing heterocycles such as a benzothiadiazole ring.