Berlin 2012 – wissenschaftliches Programm
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HL: Fachverband Halbleiterphysik
HL 34: Organic Electronics and Photovoltaics: Simulations and Optics I (jointly with DS, CPP, O)
HL 34.1: Vortrag
Dienstag, 27. März 2012, 09:30–09:45, H 2032
Excited states of terminally dicyanovinyl-substituted oligothiophenes and C60: Frenkel vs. charge-transfer excitons — •Björn Baumeier1, Denis Andrienko1, and Michael Rohlfing2 — 1Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany — 2Department of Physics, University of Osnabrück, Barbarastr. 7, 49076 Osnabrück, Germany
Excited states of terminally dicyanovinyl-substituted oligothiophenes (DCVnT) and C60, a donor-acceptor combination used in state-of-the-art small-molecule-based organic photovoltaic devices, are studied using ab initio many-body Green’s functions theory within the GW approximation and the Bethe-Salpeter equation. Calculations including resonant-antiresonant transition coupling and dynamical screening for DCVnT monomers yield excitation energies in excellent agreement with spectroscopic data. More importantly, it is possible with this approach to explicitly treat excited states in model dimers of DCVnT and C60. This in particular allows to gain nanoscale insight into the relative energies of local (Frenkel) and charge-transfer excitations, which influence the charge generation in devices.
We will present results for model systems of DCV4T:C60 and DCV5T:C60 and will analyze the dependence of the relative excitations on, e.g., the arrangement of donor and acceptor molecules in the dimer and the length of the donor, as well as discuss the consequences for performance in organic photovoltaic devices.