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