Functionalized Solid Solubilizer for Modulating Residual PbI₂ toward Efficient and Stable Perovskite Solar Cells

Controlling the aggregation of residual lead iodide (PbI₂) during the perovskite crystallization process is crucial for enhancing the power conversion efficiency (PCE) and stability of perovskite solar cells (PSCs). Herein, a functional solid solubilizer named 1-acetylpyridinium chloride (APC) is incorporated into the perovskite precursor for effectively suppressing the aggregation of residual PbI₂. The carbonyl and pyridine groups in APC form multisite interactions with PbI₂, effectively increasing its solubility, inhibiting the accumulation of residual PbI₂ during perovskite crystallization, and thereby improving film uniformity. The resulting film exhibits vertically oriented grains, without obvious PbI₂ aggregation observed either on the surface or in the bulk, along with a significantly reduced defect density. Benefiting from the effective passivation of PbI₂-rich phases, the PSCs fabricated with APC achieve a champion PCE of 24.87%, much higher than that of the control (23.34%). Moreover, the introduction of APC continuously suppresses the formation of PbI₂ during device fabrication, enhancing the long-term stability of the devices. The target devices retain 90% of their initial average PCE after 1500 h of storage under a N₂ atmosphere at room temperature. Our work offers a simple and feasible strategy for controlling the random aggregation of residual PbI₂ and fabricating highly efficient and stable PSCs.