Ultraviolet-light–dark cycle analysis of degradation in perovskite solar cells

The stability of perovskite solar cells must be evaluated under realistic outdoor conditions, such as light–dark cycles, because their reversible performance changes under such conditions. Therefore, in this study, we performed light–dark cycle analysis of lead halide perovskite solar cells under ultraviolet (UV) light irradiation to evaluate their metastability and UV degradation. The power drop under UV irradiation was recovered after storing the cells in dark because of ion-migration effects. Furthermore, the energy yield during 6 h of UV irradiation reduced slightly during the light–dark cycles, similar to the reduction in energy yield observed under a white-light-light-emitting diode. This change in energy yield indicates that the power drop observed after 6 h of UV irradiation cannot be attributed to UV-induced degradation of the perovskite used in this study. Our findings show that light–dark cycle analyses are effective for distinguishing between metastability and UV-induced material degradation.