Modified molecule-substrate coupling in self-assembled donor-acceptor nanostructures

Charge transfer processes between donor-acceptor complexes and metallic electrodes are at the heart of novel organic optoelectronic devices such as solar cells. Here, a combined approach of surface-sensitive microscopy, synchrotron radiation spectroscopy, and state-of-the-art ab initio calculations is used to demonstrate the delicate balance that exists between intermolecular and molecule-substrate interactions, hybridization, and charge transfer in model donor-acceptor assemblies at metal-organic interfaces. It is shown that charge transfer and chemical properties of interfaces based on single component layers cannot be naively extrapolated to binary donor-acceptor assemblies. In particular, studying the self-assembly of supramolecular nanostructures on Cu(111), composed of fluorinated copper- phthalocyanines (F16CuPc) and diindenoperylene (DIP), it is found that, in reference to the associated single component layers, the donor (DIP) decouples electronically from the metal surface, while the acceptor (F16CuPc) suffers strong hybridization with the substrate.