A Eu 3+ -Eu 2+ ion redox shuttle imparts operational durability to Pb-I perovskite solar cells

A redox road to recovery Device longevity is a key issue for organic-inorganic perovskite solar cells. Encapsulation can limit degradation arising from reactions with oxygen and water, but light, electric-field, and thermal stresses can lead to metastable elemental lead and halide atom defects. Wang et al. show that for the lead-iodine system, the introduction of the rare earth europium ion pair Eu 3+ -Eu 2+ can shuttle electrons and recover lead and iodine ions (Pb 2+ and I − ). Devices incorporating this redox shuttle maintained more than 90% of their initial power conversion efficiencies under various aging conditions. Science , this issue p. 265