Optical Properties of Blends: Influence of Mixing-Induced Disorder in Pentacene:Diindenoperylene versus Perfluoropentacene:Diindenoperylene

The optical properties of mixed films of pentacene:diindenoperylene and perfluoropentacene:diindenoperylene in various mixing ratios are studied using spectroscopic ellipsometry and polarization dependent transmission spectroscopy. Compared to the spectra of films of the pure compounds, the absorption spectra of the blends are found to be significantly influenced by interactions of the comixed compounds and the mixing-induced disorder. On the basis of the comparison of the two mixed systems, we address the effects of mixing and ordering behavior on the specific optical transitions of the different blends by analyzing the line shape of the spectra and the energy positions and widths of the characteristic peaks. The results are important for a fundamental understanding of organic semiconductor blends and possible charge transfer effects in these systems relevant for device applications.