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Hybrid interfaces

The Soft Matter Physics group is also a member of the Collaborative Research Center "Hybrid Inorganic/Organic Systems for Opto-Electronics", CRC 951 (HIOS). Within this project the group focuses on fundamental electronic properties of interfaces between inorganic and organic semiconductor materials. Aiming at a conclusive, possibly quantitative, understanding, the mechanisms of charge transfer across as well as the nature of hybrid charge transfer excitons formed at such interfaces are of our particular interest.

In our current research, we combine transparent metal oxides such as ZnO and SnO2 with organic semiconductor materials in a planar geometry with a well-defined, flat interface. These structures form hybrid photovoltaic cells. We employ temperature dependent photovoltaic characterization, electroluminescence (EL) spectroscopy as well as spectrally resolved photocurrent measurements in order to probe the electronic processes at the hybrid interface. Recently, we demonstrated for the first time a direct correlation between the energy of the hybrid CT state emission, the interface energetics found by UPS and the open circuit voltage of such hybrid inorganic/organic devices.

Photo: The Journal of Physical Chemistry Letters 6, 500-504 (2015)
Sketch of the hybrid charge transfer states (HCTS) at the planar interface between α-NPD and ZnO

F. Piersimoni, R. Schlesinger, J. Benduhn, D. Spoltore, S. Reiter, I. Lange, N. Koch, K. Vandewal & D. Neher, “Charge Transfer Absorption and Emission at ZnO/Organic Interfaces”, The Journal of Physical Chemistry Letters6, 500-504 (2015), DOI: 10.1021/jz502657z

I. Lange, S. Reiter, J. Kniepert, F. Piersimoni, M. Pätzel, J. Hildebrandt, T. Brenner, S. Hecht & D. Neher, “Zinc oxide modified with benzylphosphonic acids as transparent electrodes in regular and inverted organic solar cell structures”, Applied Physics Letters106, 113302 (2015), DOI: 10.1063/1.4916182

I. Lange, S. Reiter, M. Pätzel, A. Zykov, A. Nefedov, J. Hildebrandt, S. Hecht, S. Kowarik, C. Wöll, G. Heimel & D. Neher, "Tuning the Work Function of Polar Zinc Oxide Surfaces using Modified Phosphonic Acid Self-Assembled Monolayers", Advanced Functional Materials24, 7014-7024 (2014), DOI: 10.1002/adfm.201401493