Active members
Dr. Sonja Schröder
PhD Student Forschungszentrum JülichQuantum Nanoscience (PGI-3)Biographical Info
2017 |
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| 2. | S. Schröder Structural and electronic characterization of hetero-organic NTCDA-CuPc adsorbate systems on Ag(111) PhD Thesis 2017, ISBN: 978-3-95806-239-9. @phdthesis{Schröder2017,Ching Tang and Steven van Slyke invented the first organic light emitting diode (OLED)in 1987 after they discovered that light can be emitted by passing current througha carbon-based material [TV87]. Since then organic molecules have been used additionally in organic field transistors (OFETs) [KTA03] and photovoltaic cells (OPVC)[YSF05]. Organic solar cells are very promising as they have many advantages compared to inorganic devices: 10 times thinner active layers are sufficient, the costs are much less and the production is easier. To compete with inorganic solar cells however the efficiency of the organic solar cells has to be increased by a factor of 2-3 [Kie07]. For further development and an increase of the efficiency of these devices, different materials have been studied as small organic molecules and polymers. This should lead to deeper knowledge of fundamental mechanisms at organic-metal and organic-organic interfaces, in order to find the material of choice. Many different homomolecular prototype systems of semiconducting molecules on metals have therefore been investigated extensively in the last decade [Tau07], [For97], [EBST04], [BLC+10], [SHK+09], [KSS+10], [DGS+07]. Studying the formation of the first layer is necessary as it is crucial for the growth of the subsequent layers [BCK05], in the end defining the properties of the organic device. [...] |
2015 |
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| 1. | B. Stadtmüller, S. Schröder, C. Kumpf Heteromolecular metal-organic interfaces: Electronic and structural fingerprints of chemical bonding Journal Article In: J. Elec. Spec. Relat. Phenom., vol. 204A, pp. 80-91, 2015. @article{Stadtmüller2015,Beside the fact that they attract highest interest in the field of organic electronics, heteromolecular structures adsorbed on metal surfaces, in particular donor–acceptor blends, became a popular field in fundamental science, possibly since some surprising and unexpected behaviors were found for such systems. One is the apparent breaking of a rather fundamental rule in chemistry, namely that stronger chemical bonds go along with shorter bond lengths, as it is, e.g., well-known for the sequence from single to triple bonds. In this review we summarize the results of heteromolecular monolayer structures adsorbed on Ag(111), which – regarding this rule – behave in a counterintuitive way. The charge acceptor moves away from the substrate while its electronic structure indicates a stronger chemical interaction, indicated by a shift of the formerly lowest unoccupied molecular orbital toward higher binding energies. The donor behaves in the opposite way, it gives away charge, hence, electronically the bonding to the surface becomes weaker, but at the same time it also approaches the surface. It looks as if the concordant link between electronic and geometric structure was broken. But both effects can be explained by a substrate-mediated charge transfer from the donor to the acceptor. The charge reorganization going along with this transfer is responsible for both, the lifting-up of the acceptor molecule and the filling of its LUMO, and also for the reversed effects at the donor molecules. In the end, both molecules mutually enhance their respective donor and acceptor characters. We argue that this effect is of general validity for π-conjugated molecules adsorbing on noble metal surfaces. |
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