SKM 2021 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 19: Poster Session IV
HL 19.10: Poster
Thursday, September 30, 2021, 13:30–16:30, P
Ultrafast energy transfer triggers ionization energy offset dependent quantum yields in low-bandgap NFA solar cells — •Julien F. Gorenflot1, Safakath Karuthedath1, Yuliar Firdaus1, Catherine S. De Castro1, George Harrison1, Anastasia Markina2, Neha Chaturvedi1, Jafar Khan1, Ahmed H. Balawi1, Sri H. K. Paleti1, Thomas Anthopoulos1, Derya Baran1, Denis Andrienko2, and Frédéric Laquai1 — 1KAUST Solar Center (KSC), Material Science and Engineering program (MSE), Physical Science and Engineering division (PSE), King Abdullah University of Science and Technology, Thuwal, Saudi Arabia. — 2Max Planck Institute for Polymer Research, Mainz, Germany.
Organic solar cells associate an electron donor and an electron acceptor to drive exciton-to-charge conversion where the strong EA acceptor attracts electrons from donor excitons, and the low IE donor attracts holes from acceptor excitons. Recent studies however, claim efficient photocurrent generation in recent non-fullerene acceptor (NFA) based systems with close-to-zero IE or EA offsets. Here, we confirm that sizeable IE offsets are required to drive hole transfer from acceptor exciton. Further charge separation from the interface is however barrierless. Due to fast, Förster Resonant Energy Transfer to the low bandgap acceptor, charge transfer always occurs from the acceptor, making the EA offset unimportant. We model the IE offset dependence of hole transfer and find that two physical parameters are sufficient to describe it. Our model also explains barrierless charge separation and the high charge transfer states energies reported in NFA-based systems.