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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 56: Focus: Exploitation of Anisotropy in Organic Semiconductors II (joint session CPP/HL)
CPP 56.5: Vortrag
Mittwoch, 18. März 2020, 10:45–11:00, ZEU 222
Anistropic Charge Transfer Formation at Crystalline Pentacene/Perfluoropentacene Interfaces — •Sebastian Hammer1, Clemens Zeiser2, Katharina Broch2, and Jens Pflaum1,3 — 1Experimental Physics VI, Julius Maximilian University of Würzburg, 97074 Würzburg — 2Institute for Applied Physics, University of Tübingen, 72076 Tübingen — 3ZAE Bayern, 97074 Würzburg
Strongly bound charge transfer (CT) states critically influence the performance of devices based on donor/acceptor (D/A) heterojunctions such as light emitting diodes or photovolatic cells. Whereas the excited states in the archetypical CT system Pentacene:Perfluoropentacene (P:PFP) have been vastly studied in thin films [1][2], the role of molecular orientation on CT formation and energetics has not been evaluated to the same extent, so far. Utilizing heteroepitaxial growth of PFP on P (001) single crystals surfaces we were able to prepare long-range ordered D/A heterojunctions in an edge-on molecular configuration as confirmed by XRD. Optical analyses by temperature dependent cw-fluorescence spectroscopy and in-situ differential reflectance spectroscopy on the PFP/P interfaces revealed no indication for CT formation in case of edge-on molecular orientation, in contrast to the face-to-face geometry. By means of bilayer as well as heterojunction diode structures we demonstrate that by controlling the molecular orientation at the PFP/P interface, thus, utilizing the anisotropic CT characteristics, the overall performance can be significantly improved.
[1] K. Broch et al., Phys. Rev. B 83, 245307 (2011)
[2] T. Breuer, G. Witte, J. Chem. Phys. 21, 138 (2013)