Pyrenesulfonic Acid Sodium Salt for Effective Bottom‐Surface Passivation to Attain High Performance of Perovskite Solar Cells

In perovskite solar cells, not only defects on the top perovskite film surface seriously affect device performance, those buried in the bottom perovskite–electron‐transfer layer (ETL) interface damage carrier extraction, transport, and device efficiency as well. Herein, a novel double‐sided passivation strategy is designed using a single π‐conjugation‐induced 1‐pyrenesulfonic acid sodium salt (PyNa + ). It is found that it effectively passivates top and bottom interface defects to render high device performance. The π‐conjugated pyrene‐containing sodium salt electronically contributes to the surface band edges and influences the carrier dynamics by passivating defects at both top hole‐transfer layer (HTL)–perovskite and bottom perovskite–ETL interfaces. The density functional theory (DFT) calculation confirms that the Pb cluster and I—Pb antisite defects can be effectively passivated by the O···Pb coordination and electrostatic interaction of PyNa + . The carrier lifetimes are prolonged, the interface defect density is effectively reduced as measured by space‐charge‐limited current (SCLC). Through the double layer passivation of PyNa + , the device delivers improved power conversion efficiencies of 21.22% relative to that of a reference perovskite, and enhanced stability with 85% of original efficiency after 1440 h in atmospheric environment. Double‐sided passivation provides a comprehensive strategy for high‐performance perovskite solar cells.