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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 1: Focus: Organic Solar Cells Based on Non-fullerene Acceptors: Loss Mechanism and Options for Above 20 % Efficiencies I
CPP 1.10: Talk
Monday, March 27, 2023, 12:30–12:45, GÖR 226
Efficient Nanoscale Exciton Transport in Non-fullerene Organic Solar Cells Enables Reduced Bimolecular Recombination of Free Charges — •Drew B. Riley1, Oskar J. Sandberg1, Nasim Zarrabi1, Ryun Kim2, Paul Meredith1, and Ardalan Armin1 — 1Swansea Univeristy, Swansea, Wales. — 2Cambridge Univeristy, Cambridge, UK
The origins of reduced bimolecular recombination in high efficiency OPV-based solar cells are debated, and mechanisms related to the charge-transfer (CT) state and free-carrier encounter dynamics have been proposed as underlying factors.[1] Further, it is expected that the CT-state dynamics is strongly influenced by exciton dynamics in low off-set blends.[2]
In this presentation I will explore the role exciton dynamics play in the charge generation and recombination processes. Specifically, I will introduce a photoluminescence-based probe to quantify the acceptor domain size in OPV blends. It will be shown that NFA-based blends form larger domains than fullerene-based systems but that this increase is unable to account for the observed non-Langevin recombination. Further, I will show that the reduction of bimolecular recombination is correlated with enhanced exciton dynamics within the NFA domains. This indicates that the processes responsible for efficient exciton transport also enable strongly non-Langevin recombination in high efficiency NFA-based solar cells with low energy offsets.
[1] A. Armin, et.al. AEM, 11, 2003570, 2021.
[2] A. Classen,et.al. Nat.Energy, 5,2020.