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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 49: Organic Electronics and Photovoltaics IV
CPP 49.4: Vortrag
Freitag, 22. März 2024, 10:15–10:30, H 0107
On the role of energy level offset and exciton reformation in non-geminate recombination of organic solar cells — •Nurlan Tokmoldin1, Dieter Neher2, and Safa Shoaee1,3 — 1Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., 10117 Berlin, Germany — 2Soft Matter Physics and Optoelectronics, Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam-Golm, Germany — 3Optoelectronics of Disordered Semiconductors, Institute of Physics and Astronomy, University of Potsdam, D-14476 Potsdam-Golm, Germany
The performance of modern organic bulk-heterojunction solar cells relies on a transition from a localised singlet exciton on an acceptor molecule (S1) to a charge-transfer state (CT), followed by CT dissociation into separated charge (CS) carriers. The latter may afterwards either be extracted or recombine by reforming CT. Losses may occur at every stage of the free carrier generation and during their lifetime and proceed via radiative and non-radiative decay of S1 and CT. The S1 reformation efficiency from CT then comes forward as a key parameter characterizing the distribution of losses via the different channels. We employ a rate equation analysis to determine the singlet reformation efficiency for several low-offset organic solar cells and find a good correlation with the S1-CT offsets extracted from temperature-dependent electroluminescence quantum yield measurements. This supports our earlier observations that the energy offset affects the bimolecular recombination coefficient in OPV blends and indicates that exciton reformation may indeed act a channel for non-geminate recombination.
Keywords: organic solar cell; energy offset; singlet exciton reformation; charge-transfer state