Lithium‐Ion Endohedral Fullerene (Li⁺@C₆₀) Dopants in Stable Perovskite Solar Cells Induce Instant Doping and Anti‐Oxidation

Herein, we report use of [Li + @C 60 ]TFSI − as a dopant for spiro‐MeOTAD in lead halide perovskite solar cells. This approach gave an air stability nearly 10‐fold that of conventional devices using Li + TFSI − . Such high stability is attributed to the hydrophobic nature of [Li + @C 60 ]TFSI − repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li + @C 60 ]TFSI − could oxidize spiro‐MeOTAD without the need for oxygen. The encapsulated devices exhibited outstanding air stability for more than 1000 h while illuminated under ambient conditions.