Multifunctional Molecular Design of a New Fulleropyrrolidine Electron Transport Material Family Engenders High Performance of Perovskite Solar Cells

[6,6]‐phenyl‐C61‐butyric acid methyl ester remains indispensable as the electron transport material (ETM) for perovskite solar cells (PSCs), but its synthesis involves complicated multisteps with low productivity. In contrast, the potential of synthesizing simpler fulleropyrrolidine derivatives has long been overlooked, and little has been understood regarding their structure‐dependent effects on photovoltaic (PV) performance. Herein, seven novel fulleropyrrolidine derivatives (F1–F7) are deliberately designed, synthesized, and comprehensively characterized in both solution and thin‐film states and subsequently investigated as ETMs for PSCs. Notably, the F4 delivers the highest power conversion efficiencies over 20% of devices, which surpass all reported fulleropyrrolidine ETMs due to its optimal photoelectric property. Moreover, the structure‐dependent effects of the fullerenes on PV parameters are uncovered, including solubility, intermolecular interaction, packing structure, and charge‐transfer ability, which can guide the future design of high‐performance and stable fullerene ETMs for PSCs. A novel fullerene molecular template with a solubility enhancer arm (R1) and a π–π interaction inducer arm (R2) is deliberately proposed. This design effort delivers the highest power conversion efficiency over 20% of the device with corresponding fulleropyrrolidine electron transport material for the first time.