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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 31: Organic Electronics and Photovoltaics II
CPP 31.1: Talk
Wednesday, March 20, 2024, 15:00–15:15, H 0110
N-type charge transfer complex in DBTTF:HATCN mixtures — •Hongwon Kim1, Andreas Opitz2, Marie Siegert3, Lennart Frohloff2, Jens Pflaum3, and Wolfgang Brütting1 — 1Experimental Physics IV, Institute of Physics, University of Augsburg, Germany — 2Supramolecular System, Institute of Physics, Humboldt University of Berlin, Germany — 3Experimental Physics VI, University of Würzburg, Germany
Mixtures of the electron donor DBTTF and the acceptor HATCN form a charge transfer complex (CTC), which leads to the appearance of new optical absorption bands below the band gap of the two pristine materials and a significant enhancement of the electrical conductivity. We prepared thin films by co-evaporation through systematic variation of their mixing ratio from pure DBTTF to pure HATCN and measured the temperature-dependent conductivity as well as charge carrier concentration and mobility. Surprisingly, we found n-type behavior for all compositions, except pure DBTTF. This can be understood from the electronic structure of the mixtures through ultraviolet photoelectron spectroscopy (UPS), which conclusively indicate that charge injection and transport occurs via the lowest unoccupied molecular orbital (LUMO) of the CTC. Furthermore, insight into the rich behavior of the electrical conductivity can be gained from morphological studies using Atomic Force Microscopy (AFM).
Keywords: organic semiconductor; charge transfer complex; electical conductivity; carrier mobility