Excitation Intervals Enhance Performance in Perovskite Solar Cells.

Halide perovskites face intrinsic stability challenges primarily due to light- and bias-induced ion migration. To mitigate ion-mediated degradation on operationally relevant time scales, this work investigates how introducing brief periodic intervals of light and darkness (LD cycling) can stabilize the average efficiency of perovskite films and devices. Systematic photoluminescence (PL) studies reveal that dark intervals on the order of seconds significantly suppress nonradiative recombination and slow degradation. The extent of PL enhancement depends on the duration of the dark time, the material composition, and critically, the sample's age. Remarkably, LD cycling increases PL by more than 7-fold even in aged samples that would otherwise undergo photodarkening under continuous illumination. Moreover, the PL kinetics under LD cycling mirror the corresponding open-circuit voltage dynamics in full solar cells, showing that local emission changes provide a direct measure of device-level behavior. Device measurements similarly show that LD cycling enhances the power conversion efficiency compared to continuous illumination and mitigates deterioration over extended operation. This strategy highlights a potential pathway to dynamically preserve or even improve perovskite performance in future optoelectronic applications.