Hamburg 2001 – wissenschaftliches Programm
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SYOF: Organische Festkörper
SYOF 5: Poster Session
SYOF 5.20: Poster
Dienstag, 27. März 2001, 17:00–19:00, Aula S3
Tuning the optical properties of thiophene oligomers - A theoretical study — •G. Daminelli1, J. Widany1, A. Di Carlo1, P. Lugli1, T. Niehaus2, and T. Frauenheim2 — 1Dipartimento di Ingegneria Elettronica, Università di Roma II “Tor Vergata”, I-00133 Roma, Italy — 2Theoretische Physik, Fachbereich Physik, Universität-Gesamthochschule, D-33098 Paderborn, Germany
The absorption properties of thiophene-based molecules with various substituents have been studied using a time-dependent density-functional based tight-binding scheme. Correlations between structural and electronic properties are discussed.
Modified ter-, quinque- and epta-thiophenes, showing enhanced emission efficiencies, have been choosen as parent molecules. Electron withdrawing or donating substituents have been placed on the two terminal thiophene units in α, β and β’ position with respect to the sulphur atom of the thiophene.
The presence of substituents has in general only minor effects on the geometry of the parent molecules, but strong influence on the optical properties. Electron donating groups in α position cause an increasing absorption red shift with stronger donating character of the group. In the case of electron withdrawing groups, no direct relation can be observed between the character of the group and the shift. The shift effect of β substitution is much weaker: Electron withdrawing groups as -CN, -NO2 and -CSCH3 cause a slight blue shift, weak electron donating moieties as -OCH3 and -SCH3 do not induce spectral changes, while strong electron donors as -NH2 and -N(CH3)2 lead to a small red shift.