Dr. Roberto Otero, Dept de Física de la Materia Condensada, Universidad Autónoma de Madrid & IMDEA-Nano, Madrid, Spain

Charge-Transfer Effects at the Metal/Organic Interface

The working principle underlying organic optoelectronic of photovoltaic devices is ultimately based on the transfer of electron charge across metal/organic interfaces. This charge-transfer process is known to be determined not only by the electronic properties of the organic and metallic sides of the junction, but also on its structural properties (layer density, number of defects, etc.) While much has been learnt during the last few years about the adsorption and self-assembly of organic material on metal substrates in the limit of weak molecule-substrate interaction, much less is known for the case in which this interaction is non-negligible. The molecules used in practical applications in organic electronic devices need to have a rather strong donor or acceptor character from the electronic point of view, leading to the expectation of spontaneous charge-transfer processes between the metal and the organic layer which are usually associated with a rather strong molecule-substrate interaction. In this talk we will explore the multiple effects that charge-transfer between strong organic acceptors and a metal substrate has on the adsorption geometry, adsorption conformation, molecular self-assembly and chemical stability of the organic layer. We will show that the transfer of electrons from the metal to the organic layer affects in a decisive way the mechanical flexibility of the adsorbates, which in turn leads to chemical reactions and aggregation patterns that would have been impossible to predict in the weak molecule-substrate interaction limit. Such effects should be properly accounted for in order to engineer the interfaces in organic optoelectronic and photovoltaic devices, thereby optimizing their performance.

• T.-C. Tseng et al. Nature Chemistry 2, 374 (2010)
• C. Urban et al. ChemComm 50, 833 (2014)