Regensburg 2007 – wissenschaftliches Programm
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SYOE: Symposium Organic Thin Film Electronics: From Molecular Contacts to Devices
SYOE 8: Poster Session SYOE
SYOE 8.107: Poster
Dienstag, 27. März 2007, 18:00–20:00, Poster B
Vertically and relaxed excited state properties of neutral and charged oligofluorenses with and without keto-defect — •Mengtao Sun2, Wichard J.D. Beenken1, Tõnu Pullerits3, and Guangjiu Zhao4 — 1Technische Universität Ilmenau, FG Theoretische Physik I, Postfach 100565, 98684 Ilmenau, Germany — 2Chinese Academy of Sciences, Institute of Physics, Beijing, 100080, P. R. China — 3Lunds Universitet, Kemisk Fysik, Box 124, 22100 Lund, Sweden — 4Dalian Institute of Chemical Physics, State Key Laboratory of Molecular Reaction Dynamics, Dalian, 116023, P. R. China
Oxidation is one of the main degradation problems in conjugated polymers. Stimulated from the recent experimental report of optical properties of charged oligofluorenes [Fratiloiu, S; et al. J. Phys. Chem. B 2006, 110, 5984-5993], we studied the electronic structure and optical properties of neutral and charged oligofluorenses with and without the keto-defect by time-dependent density functional theory (TD-DFT). Using 2D site and 3D cube representations of the density matrix, we found the vertically and relaxed excited states (i.e. absorption and emission) for the neutral species being like Frenkel-excitons. For both charged species, however, the first excited states represent spatial oscillations of the electron-hole pair over the whole oligomer chain. A single keto-defect forming a central fluorene-9-on monomer strongly affects the excited states of the neutral and anionic oligo-fluorenes by getting strong charge-transfer character, while those of the cation are nearly unchanged.