Dual-Functional Molecular Stabilization of Spacer Cation-Mediated Aging Dynamics in Low-Dimensional Perovskite Precursors Enables Efficient Solar Cells.

The aging dynamics of perovskite precursor solutions critically govern the photovoltaic performance of solar cells. However, the underlying degradation mechanisms in low-dimensional perovskite precursors remain elusive, particularly regarding the pivotal role of spacer cations in modulating decomposition pathways. This study elucidates the intrinsic aging mechanisms in low-dimensional perovskite precursors, revealing that spacer cation integration fundamentally governs decomposition kinetics. A dual-functional solution stabilizer, 4-carboxy-2-fluorophenylboronic acid (CFB), is strategically designed to concurrently mitigate precursor degradation and regulate crystallization dynamics. The carboxyl moiety undergoes spontaneous deprotonation to establish robust hydrogen bonds with guanidinium (GA+), effectively suppressing methylamine (MA0)-mediated nucleophilic attacks and preventing irreversible addition-elimination reactions between GA+ and MA0. Simultaneously, CFB orchestrates multi-stage crystallization control through coordination modulation, yielding highly oriented perovskite crystals with passivated grain boundaries. The optimized devices demonstrate exceptional photovoltaic performance with a remarkably low energy loss of 0.38 eV. Notably, devices fabricated from aged precursors maintain 90% of initial efficiency over 42 days of ambient storage. Furthermore, unencapsulated devices deliver optimized humidity stability and thermal stability.