Fundamental investigations on mixing in organic blend layers
January 2018
The field of organic electronics has attracted great interest from the industry within the past years. Flexible, light-weight, efficient and low-cost electronic devices such as organic light-emitting diodes or solar cells have created a growng multi-billion euro market. However, organic electronics are also still ahighly relevant topic for fundamental research since a basic understanding of how molecular properties can be translated into device properties is still missing.
We recently made an important step toward creating this understanding. We found that molecular energy levels of organic semiconductor molecules can be manipulated by long-range charge-quadrupole interactions in thin films [1]. This effect allows us to engineer the electronic bands in blended films which is a key necessity to control important parameters of organic electronic devices – in particular the open-circuit voltage in organic solar cells. The mixing of the molecules in the blended layers has a great impact on the quadrupole field. However, in order to calculate the quadrupole field a precise knowledge of the molecular arrangement is needed.
In cooperation with the Leibniz Institute for Polymer Research (IPF), we have the opportunity to carry out Nuclear Magnetic Resonance Spectroscopy (NMR) on our layers to determine the distance between fluorinated molecules in a blend with non-fluorinated molecules. Therefore, one part of this thesis is the calculation of the expected atom distances which is essential for interpreting the measurement data. The experimental part of the thesis includes the preparation of samples in our vacuum cluster tool and performing measurements, such as absorption or X-ray diffraction (XRD). This investigation is closely affiliated to an ongoing study at the IAPP aiming to describe the energy level alignment and the structural arrangement of the mole-cules within blend layers. Therefore, the applicant will also get a close insight into other techniques such as ultra-violet photoelectron spectroscopy and electron microscopy techniques.
The IAPP is a place where more than 120 physicists, chemists and engineering are working together on allvirtually topics related to organic electronics – fundamentals and applications. Hence, the IAPP provides a perfect platform for the applicant to interact with other scientists in order to get a broad overview on other research topics on organic electronics.
References:
[1] M. Schwarze et al., „Bandstructure engineering in organic semiconductors“, Science 352 (6292), 1446-1449 (2016).
contact person:
Dr. Hans Kleemann
Arbeitsgruppe ODS (Organic Devices and Structures)
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