Dynamics of charge separation in polymer:fullerene blends, correlating structural and photophysical length scales

Organic solar cells are undergoing a revival with the discovery of non-fullerene electron acceptors, achieving relatively high photovoltage and light harvesting yields compared to older fullerene systems. There are however scientific questions regarding their excited state dynamics which continue to be unresolved including the role of singlet and triplet excited states before and after charge generation at the electron donor-acceptor interface in the device photoactive area. The presentation will discuss our recent progress in understanding the diffusion of excited states in non-fullerene electron acceptors before charge transfer and the charge dynamics after generation, based on time-resolved laser spectroscopy experiments covering timescales from femto- to microseconds. Our analysis sheds light on the importance of both interfacial energetics and molecular packing on the excited state dynamics.