Thermally Activated Reverse Electron Transfer Limits Carrier Generation Efficiency in PM6:Y6 Non?Fullerene Organic Solar Cells

Transient absorption and time-resolved fluorescence measurements in a wide temperature range are used to investigate the mechanism of charge carrier generation efficient organic solar cells based on PM6:Y6 donor–acceptor blend. The mechanisms differ significantly under excitation donor or acceptor. investigations reveal temperature-dependent interplay between formation interfacial transfer (CT) states intra-moiety CT acceptor, their separation into free carriers recombination. is ensured by over small energy barrier, which easily surmountable at room temperature. However, overall yield reduced recombination due thermally activated back electrons from acceptor via highest occupied molecular orbit (HOMO) levels, enabled offset HOMO levels