Crystallization Manipulation Through Buried Pyridinium-Induced Tunable Interactions in Perovskite Solar Cells

The interaction between the hybrid component of self-assembled monolayers (SAMs) and the perovskite precursor could delay the crystallization process, resulting in high-quality perovskite film and highly efficient perovskite solar cells (PSCs). However, the intensity of interaction affects more precise control of crystallization speed. Herein, we introduce two pyridinium cation species to compare the intensity of their interaction with iodide. Our systematic investigation reveals that the more electron deficient 1-methyl-4-(trifluoromethyl)pyridinium (CF₃Py⁺)-based hybrid SAM enables a champion power conversion efficiency (PCE) of 27.07% (certified 26.8%) for a 0.06-cm² PSC, surpassing hybrid 1-methylpyridinium (Py⁺)-based device (26.42%) and pure 4PADCB-based device (25.12%). The impressive PCE stems from fine-tuning of crystallization speed through more intensive interaction between CF₃Py⁺ and I^-. Moreover, the stronger interaction inhibits iodide migration, which improves the light and thermal stability of the optimized PSCs. Our work demonstrates an effective approach to strengthening the interaction between pyridinium cations and iodide by incorporating an electron-withdrawing group into the aromatic core, providing crucial insights into the manipulation of perovskite film crystallization.