Dresden 2020 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 76: Organic semiconductors II (joint session HL/CPP)

CPP 76.1: Invited Talk

Wednesday, March 18, 2020, 15:00–15:30, POT 112

Ultrafast nonadiabatic dynamics and intermolecular conical intersections in organic photovoltaic materials — •Antonietta De Sio — Institut für Physik, Universität Oldenburg

Conjugated polymer and molecular aggregates, used as photoactive materials in organic optoelectronic devices, are large supramolecular assemblies which often present complex energy landscapes and many vibrational degrees of freedom. Coupling of electronic and nuclear motion in molecules may lead to special topologies of potential energy surfaces, such as conical intersections (CoIns). At CoIns, strong vibronic couplings drive ultrafast and efficient nonadiabatic transitions between electronic states and may thus profoundly influence the ultrafast pathways of energy flow and motion of charges. CoIns are of key importance in many photochemical and biological intramolecular processes. So far, however, not much is known about their possible occurrence and relevance for intermolecular excitations in functional condensed-phase assemblies. Here we discuss how ultrafast two-dimensional electronic spectroscopy (2DES) can provide detailed insight into vibronic couplings and nonadiabatic dynamics in technologically relevant organic materials. Specifically, high-time resolution 2DES allows us to experimentally reveal the ultrafast, sub-50-fs passage of a coherent vibrational wavepacket through an intermolecular CoIn in molecular aggregate thin films used in organic photovoltaics. Our results suggest that vibronic couplings and CoIns may help to efficiently steer the energy flow in functional nanostructures, thus opening up new opportunities for controlling transport in organic-based devices.