Regensburg 2025 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 54: Ultra-fast Phenomena II
HL 54.1: Talk
Thursday, March 20, 2025, 15:00–15:15, H17
Effect of the acceptor strength on intermolecular conical intersection dynamics in aggregates of quadrupolar dyes — •Katrin Winte1, Somayeh Souri1, Daniel Lünemann1, Teresa Kraus2, Elena Mena-Osteritz2, Peter Bäuerle2, Sergei Tretiak3, Antonietta De Sio1, and Christoph Lienau1 — 1Oldenburg University, Germany — 2Ulm University, Germany — 3Los Alamos National Laboratory, USA
Aggregated films of quadrupolar acceptor-donor-acceptor (A-D-A) molecules have emerged as promising materials for organic photovoltaics. The optoelectronic properties in the molecule are governed by an interplay between electronic and vibronic couplings in the molecule. In aggregated films, we have uncovered the existence of intermolecular conical intersections (CoIn) occurring on timescales of less than 50 fs, which funnel energy from the photoexcited bright state into the lower-lying dark electronic state of the aggregate [1]. This raises the question whether the quantum dynamics of the aggregates can be altered by modifying the intramolecular charge transfer character of the A-D-A monomers. Chemical intuition suggests that increasing the acceptor strength might accelerate charge transfer and with it the passage through the CoIn. To explore this hypothesis, we synthesize thin films of A-D-A molecules with varying acceptor strengths and study their ultrafast dynamics by femtosecond time-resolved spectroscopy. Our results show only minimal effects on the CoIn dynamics, suggesting that intermolecular vibronic couplings play the dominant role in the quantum dynamics. [1] A. De Sio et al., Nature Nano 16, 63 (2021).
Keywords: Quadrupolar dyes; Nonadiabatic coupling; Ultrafast spectroscopy; Conical intersections