Regensburg 2019 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 50: Organic Electronics and Photovoltaics III - Organic Photovoltaics

CPP 50.3: Vortrag

Donnerstag, 4. April 2019, 10:00–10:15, H18

Evaluation of molecular donor-acceptor pairs forming charge-transfer or exciplex states — •Thomas Zechel, Thomas Schröther, and Wolfgang Brütting — Institute of Physics, University of Augsburg, 86159 Augsburg

Intermolecular excited states play a major role in various organic semiconductor applications. Charge-transfer (CT) states were shown to be a major contributor to large voltage losses in organic photovoltaic cells (OPVCs) and exciplex systems are becoming a viable alternative to heavy metal complexes in organic light emitting diodes (OLEDs). Both states are formed by at least two molecules of different kind (acceptor and donor). In both cases for the excited state the hole of the bound exciton resides on the donor and the electron resides on the acceptor molecule. The difference between the two being that the exciplex only exists in the excited state (no direct ground state absorption) while the CT state exhibits a small but measurable direct absorption from the ground state. This main difference is accompanied by considerably larger external electroluminescent quantum yields (EQE_EL) for exciplex systems compared to CT systems.
In this work a number of different donor-acceptor pairs which usually form exciplexes or CT states are investigated using electrical (current-voltage-luminescence, incident photon to current efficiency), optical (EL, PL) and computational (density functional theory simulations) methods to gain further insights into the differences and similarities of CT and exciplex systems on a basic material level.