Regensburg 2019 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 3: Molecular Electronics and Excited State Properties
CPP 3.9: Vortrag
Montag, 1. April 2019, 12:00–12:15, H13
Absence of Charge Transfer States at Crystalline Perfluoropentacene/Pentacene 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
The formation of charge transfer (CT) states plays an important role in charge seperation and impacts the efficiency of organic photodetectors and photovoltaics. Pentacene:Perfluoropentacene (P:PFP) has been largely studied in mixed films as a prototypical CT system by its suited donor/acceptor (D/A) energy levels [1][2]. However, the role of molecular orientation on charge transfer has not been elucidated, so far. For this purpose, we used heteroepitaxial growth of PFP on P (001) crystal interfaces to achieve long-range ordered D/A heterojunctions of edge-on molecular orientation as confirmed via X-ray diffraction. By means of temperature dependent cw fluorescence spectroscopy and in-situ differential reflectance spectroscopy we determined the optical characteristics of the PFP/P thin films and demonstrate the absence of CT state formation at the generic (001) edge-on crystalline interface. We discuss these findings with respect to possible implementation in organic solar cells where the suppression of strongly bound CT states at D/A heterointerfaces yields an increase in open circuit voltage, and thus in device performance.
[1] K. Broch et al., Phys. Rev. B 83, 245307 (2011)
[2] T. Breuer, G. Witte, J. Chem. Phys. 21, 138 (2013)