Abstract: Herein, we report use of [Li+@C60]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+@C60]TFSI− repelling moisture and absorbing intruding oxygen, thereby protecting the perovskite device from degradation. Furthermore, [Li+@C60]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. [ABSTRACT FROM AUTHOR]