Efficient Inverted Perovskite Solar Cells Enabled by Sequential Passivation Using Two‐Dimensional Perovskites

ABSTRACT Refining the process in which two‐dimensional (2D) perovskites passivate three‐dimensional (3D) perovskites is vital for improving the performance of perovskite solar cells (PSCs), yet is frequently overlooked. Herein, a novel sequential passivation process that initially employs phenethylamine iodide (PEAI) on the 3D perovskite surface, followed by treatment with 4‐trifluoromethylphenylethylamine iodide (CF 3 PEAI) is presented. A comprehensive comparison of the intrinsic molecular structures and their impact on the perovskites reveals that the small‐sized, low‐polarized PEA molecule induces minimal lattice strain and a negative shift of the vacuum energy level of perovskite surface, whereas the large‐sized, high‐polarized CF 3 PEA molecule leads to larger lattice strain and a positive shift of the vacuum energy level. By leveraging the opposing properties of these molecules through our tailored sequential passivation strategy, optimal passivation effects and efficient interface charge transfer are obtained, outperforming the posttreatment with mixed ligands and greatly surpassing posttreatment with a single ligand. Consequently, a champion efficiency of 26.27% is achieved for the inverted PSCs, along with outstanding operational stability featuring a T 80 lifetime exceeding 1000 h under continuous light illumination at the maximum power point tracking.