Ammonium salt and halogen co-functionalized fullerene for interfacial modification layer of inverted perovskite solar cells

Htigh-quality perovskite light harvesters and the interface between perovskite and charge transport layers are essential for achieving high-performing perovskite solar cells (PSCs). we introduced conductive fullerene derivatives (C60-DBI-R) co-functionalized with halogen and quaternary ammonium salt between lead perovskite and an electron transport layer (ETL) to passivate defects on the surface of perovskite, which enhances efficiency and the tolerance against moisture. The incomplete coordination of MA+ and Pb2+ on the perovskite surface are repaired by the double-site action of halogen and quaternary ammonium salt respectively, which inhibits ion migration and prevents perovskite degradation. The effects of various halogen groups on device performance are examined, and the factors contributing to their differing impacts are explored. Finally, the C60-DBI-Cl-based device achieved the highest efficiency of 20.7% and demonstrated superior stability, with 91% of its initial PCE retained after being stored at 85% relative humidity for 1000 h.