Hannover 2013 – scientific programme
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MO: Fachverband Molekülphysik
MO 14: Poster 1: Cluster, Femtosecond Spectroscopy
MO 14.15: Poster
Tuesday, March 19, 2013, 16:00–18:30, Empore Lichthof
The ultrafast dynamics of electron-transporting analogs of pentacene — •Julia Herz1, Jens Engelhart2, Tiago Buckup1, Uwe Bunz2, and Marcus Motzkus1 — 1Physikalisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany — 2Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, D-69120 Heidelberg, Germany
Pentacene derivatives are attractive targets to construct electron transporting materials in organic electronic devices. While pentacene is utilized in organic field effect transistors, the modified aza-pentacenes could find application as acceptor molecules in organic solar cells. The presence of electronegative nitrogen atoms in the systems changes the ground state as well as the excited state behaviour considerably. Transient-absorption spectroscopy allows the observation of the population flow after photo excitation. The evolution of the exciton and furthermore the formation of states and the charge generation process can be followed. We demonstrate preliminary studies of Diaza-TIPS-pentacene and Tetraaza-TIPS-pentacene in two different solvents. The ground state properties of these two molecules are presented as well as time-resolved absorption and fluorescence measurements. The influence of the nitrogen substitution and the symmetrical charge distribution on the excited state lifetimes are presented. The revealed oscillations of 270 cm−1 from the excited state are more distinctive in an unpolar solvent like toluene compared to THF. We find a pronounced concentration dependence on the excited state absorption signal, thus the aggregation of molecules in solution has to be considered.