  Strong light-matter coupling has shown great potential for modifying the
electro-optical properties of semiconducting materials in recent years. In the
strong coupling regime, excitons and cavity photons form new states named
exciton-polaritons, with their properties a hybrid of each constituent. Herein,
we report strong coupling observed in solution-processed donor:acceptor
bulk-heterojunction organic solar cells (OSCs) evidenced by the observed Rabi
splitting of ~300 meV and the effects of strong coupling on OSC operations.
Combining the transient photovoltage decay measurement and nanosecond transient
absorption spectroscopy, our results reveal that the effective charge carrier
lifetimes are longer in cavity devices, attributed to the reduced bimolecular
recombination. It is also found that access to CT state(s) of higher energy is
enabled in cavity devices. This study demonstrates that strong coupling can
effectively modify the device- and photo-physics in OSCs and opens a new
pathway for engineering more efficient OSCs.
