Synergetic Dual-Mode Interaction of Lewis Base for High Performance Perovskite Solar Cells

Regulating defects at surfaces and grain boundaries arising from uncontrolled crystallization during perovskite film formation and external stresses is crucial for improving the photovoltaic efficiency and long-term stability of perovskite solar cells (PSCs). Phosphine-based Lewis base ligands that can coordinate with Pb2+ have proven to be effective in regulating perovskite crystallization and defect passivation. However, most previous ligand strategies focus on a single point interaction. Herein, we systematically compared the tri(p-tolyl)phosphine and tris(4-methoxyphenyl)phosphine (pMeO) with different functional groups to investigate optimized ligand structure for high-quality perovskite film. Both ligands promote homogeneity and crystallinity through coordination with the Pb–I framework. pMeO exhibits dual-mode interactions by additional hydrogen bonds with organic cations through multidirectionally distributed methoxy substituents in the perovskite, enabling more uniform films with suppressed grain boundary defects and mitigating ion migration. Consequently, pMeO-treated PSCs achieve a power conversion efficiency of 25.46% with enhanced thermal and moisture stability.