| AVS 60th International Symposium and Exhibition | |
| Surface Science | Thursday Sessions |
| Session SS1-ThA |
| Session: | Organic Layers on Surfaces |
| Presenter: | K. Broch, University of Tuebingen, Germany |
| Authors: | K. Broch, University of Tuebingen, Germany A. Gerlach, University of Tuebingen, Germany C. Lorch, University of Tuebingen, Germany J. Dieterle, University of Tuebingen, Germany J. Novak, University of Tuebingen, Germany A. Hinderhofer, University of Tuebingen, Germany F. Schreiber, University of Tuebingen, Germany |
| Correspondent: | Click to Email |
As possible active layers in optoelectronic devices, binary blends of organic semiconductors are of high relevance for applications. A detailed understanding of the structure-property relation in these complex systems is crucial for device optimization, but due to the variety of film structures and associated optical properties also a challenge for fundamental research [1,2]. In particular for vacuum deposited thin films, post growth studies are often not sufficient for a detailed characterization due to possible pronounced transient effects observable during film growth [3]. These effects can include film thickness dependent changes in the average molecular tilt angle or intermolecular spacing, which may result in significant variations in the relative intensities or energy position of specific peaks in the absorption spectra [3].
Using organic molecular beam depositon we prepare thin mixed films of the prototypical organic semiconductors perfluoropentacene (PFP, C22F14) and diindenoperylene (DIP, C32H16) and follow the film growth in situ in real-time simultaneously using grazing incidence X-ray diffraction and optical spectroscopy. We discuss the result of the competing effects of strong and favourable donor-acceptor interaction and steric incompatibilities due to the size mismatch of PFP and DIP on the structure formation in mixed films, concentrating on the size of coherently scattering islands, which is related to the structural order within the films. By exploiting the advantages of a simultaneous measurement of structural and optical properties of the samples we are able to relate pronounced changes in the relative intensities of specific peaks in the optical absorption spectra to the observed changes in the structural order. The results of these experiments give insight in the complex mechanisms of structure formation and structure-property relations in mixed systems and point towards the possibility to tune the structural and optical properties for the optimization of opto-electronic devices.
[1] A. Hinderhofer and F. Schreiber, ChemPhysChem, 13, 628 (2012),
[2] A. Aufderheide et al., Phys. Rev. Lett., 109, 156102 (2012),
[3] U. Heinemeyer et al., Phys. Rev. Lett., 104, 257401 (2010),