Stabilizing Fullerene for Burn‐in‐Free and Stable Perovskite Solar Cells under Ultraviolet Preconditioning and Light Soaking

Abstract It is crucial to make perovskite solar cells sustainable and have a stable operation under natural light soaking before they become commercially acceptable. Herein, a small amount of the small molecule bathophenanthroline (Bphen) is introduced into [6,6]‐phenyl‐C₆₁‐butyric acid methyl ester and it is found that Bphen can stabilize the C₆₀‐cage well through formation of much more thermodynamically stable charge‐transfer complexes. Such a strengthened complex is used as an interlayer at the in‐light perovskite/SnO₂ side to achieve a champion device with efficiency of 23.09% (certified 22.85%). Most importantly, the stability of the resulting devices can be close to meeting the requirements of the International Electrotechnical Commission 61215 standard under simulated UV preconditioning and light‐soaking testing. They can retain over 95% and 92% of their initial efficiencies after 1100 h UV irradiation and 1000 h continuous illumination of maximum power point tracking at 60 °C, respectively.