High-efficiency and stable perovskite solar cells via bidentate chelation for facet-engineered growth of FAPbI3 (111) crystals

The long-term stability of perovskite films remains a critical challenge hindering the commercialization of perovskite solar cells (PSCs). Crystal facet engineering has emerged as one of the most promising strategies to enhance film stability. Herein, we introduce a series of bidentate nitrogen-based chelating ligands to precisely regulate the growth of perovskite films. Density functional theory calculations reveal that these ligands interact with lead ions in lead iodide, guiding perovskite crystal growth along the [111] orientation, which has been proven to possess excellent environmental stability. Furthermore, these interactions facilitate efficient charge transfer. X-ray diffraction results confirm that the chelating ligands promote preferential crystallization along the [111] direction. Long-term structural monitoring demonstrates that [111]-oriented films exhibit superior stability under ambient conditions. As a proof of concept, 3,4,7,8-tetramethyl-1,10-phenanthroline, a bidentate nitrogen-based ligand, was employed in formamidinium-lead-iodide-based PSCs, achieving a remarkable power conversion efficiency of 22.02% with exceptional operational stability. Detailed optoelectronic analyses further validated the reliability of this approach. These findings provide a mechanistic understanding of how chelating ligands stabilize perovskite films and present a viable strategy to enhance PSC performance, thus advancing their practical application in next-generation photovoltaic technologies.