Regulating Orientational Crystallization and Buried Interface for Efficient Perovskite Solar Cells Enabled by a Multi-Fluorine-Containing Higher Fullerene Derivative

Perovskite films prepared by the solution process usually result in irregular grain orientation and rich buried interface defects, hindering the further improvement of device performance. Herein, multi-fluorine-containing C-60- and C-70 (higher fullerene)-porphyrin derivatives, F60PD and F70PD, are synthesized and pre-buried to modify the SnO2/perovskite heterointerface. The F70PD modification layer provides a better perovskite quality and more effective electron transporting capability compared to the corresponding F60PD, with the F70PD being more effective in regulating the perovskite growth, passivating the buried interface defects, and optimizing the interface energy level alignment. Consequently, the F70PD-based device delivers superior efficiency and stability than the control and F60PD-based devices. The F70PD-based device yields a champion efficiency of 24.09% with negligible hysteresis. Meanwhile, due to the increased activation energy of ion migration, the F70PD-based device maintains 80% of its initial efficiency after operating at the maximum power point for 1620 h. This study highlights the potential of designing higher fullerene materials for buried interface to further improve the perovskite solar cells' performance.