Strukturforschung mit XFELs und Synchrotronstrahlung
Using mixtures of organic molecules to turn light into electric charges has long been a promising concept for renewable energy supplies but has not found widespread application due to limited efficiencies, the underlying reasons of which are not fully understood. An important model system to study these fundamental light-to-charge conversion processes consists of a combination of copper-phthalocyanine (CuPc) and C60 molecules, whereby light is absorbed in the CuPc molecules to generate so-called excitons that travel towards the interface with the C60 molecules, where they can separate into electric charges. Excitons come in different characters, designated singlet and triplet, which may have very different charge generation capabilities but they are notoriously hard to track. Our recent study provides, for the first time, relative charge generation efficiencies from singlet and triplet excitons in a CuPc-C60 heterojunction. Contrary to common belief, the slowly traveling triplet excitons contribute to a significantly larger extent to the total charge than the much faster but short-lived singlet excitons. The findings constitute an important advance in the atomic-scale understanding of the electronic dynamics underlying emerging molecular electronics concepts.
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Further reading:F. Roth, S. Neppl, A. Shavorskiy, T. Arion, J. Mahl, H. O. Seo, H. Bluhm, Z. Hussain, O. Gessner, W. Eberhardt
Efficient charge generation from triplet excitons in metal-organic heterojunctions
Physical Review B 99 (2019) 020303(R)
2 SWS Vorlesung als Blockveranstaltung am DESY in Hamburg
22. bis 27. September 2019