Strong Light–Matter Coupling Leads to a Longer Charge Carrier Lifetime in Cavity Organic Solar Cells

Strong light–matter coupling has shown great potential for modifying the electrooptical 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 being 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 the CT state(s) of higher energy is enabled in cavity devices. This study demonstrates that strong coupling can effectively modify the device and photophysics in OSCs and opens a new pathway for engineering more efficient OSCs.