Low-Concentration Pyridine-Derived Molecular Passivation for Efficient Two-Step Assistance-Free Blade-Coated FAPbI₃ Solar Cells

The two-step blade-coating method exhibits several advantages such as simple operation and high reproducibility, making it a promising scalable deposition process for high-efficiency perovskite solar cells. However, a large number of defects exist at the interface, leading to nonradiative carrier recombination losses, which negatively impact device performance and stability. Introducing pyridine derivatives at the interface to passivate defects is an effective strategy. However, most pyridine-derived molecules are used in large quantities and high concentrations, which compromises process reproducibility, reduces manufacturing reliability, and increases production costs. This study demonstrates the introduction of 3,5-Difluorpyridin-2,6-Diamin (2NF-Py) molecules at the perovskite/hole transport layer interface. Through the –NH2 group and pyridine nitrogen on the 2NF-Py molecule, which interact with interfacial uncoordinated Pb2+ and free I–, defects are effectively passivated. Meanwhile, the F group on the 2NF-Py pyridine ring increases the electrostatic center shift, thereby improving its reaction activity and enhancing its defect passivation capability. As a result, an efficiency increases from 18.07 to 21.82% was achieved at a low concentration of 0.2 mg/mL, marking the highest efficiency for perovskite solar cells (PSCs) fabricated using a two-step blade-coating process without additional assistance and the device maintained 90% of its initial efficiency after being placed in air for 1536 h.