The Kinetics of Aggregated and Non-Aggregated Phases in Y6 in Time-Resolved Pump-Probe Spectroscopy

Aggregation in non-fullerene acceptors such as Y6 is essential to achieve the high performance of current organic solar cells. In previous work,[1] we employed temperature-dependent steady-state UV-Vis absorption and photoluminescence spectroscopy combined with Franck-Condon analysis to identify the spectral signatures of two types of aggregates and the disordered phase of Y6 in solution and film. We could demonstrate how the amount and character of aggregates correlates with the device performance [2]. The simultaneous presence of aggregated and non-aggregated Y6 molecules is frequently not considered in the analysis of excited state kinetics that leads to the generation of free charges.[3] We have now identified the different signatures of aggregated and non-aggregated excited state in the fs-ns pump-probe spectra of Y6 and discuss the mechanism of charge generation under this premise.<br/>[1] Kroh et al., <i>Adv. Funct. Mater.</i> <b>2022</b>, 32, 2205711<br/>[2] Perdigón-Toro et al., <i>Adv. Energy Mater.</i> <b>2022</b>, 12, 2103422<br/>[3] Price et al., <i>Nat Commun., </i><b>2022</b>, 13, 2827