Achieving Efficient Triple-Cation Perovskite Solar Cells with Fill Factor Exceeding 86% via a Uniform Interface Passivation Strategy

Interfacial defects in triple-cation perovskite films limit device efficiency and stability, and passivation strategies often face a critical trade-off between defect coverage and charge transport. We propose a uniform interfacial passivation approach using 2-(1-cyclohexenyl)ethylammonium iodide (CHEAI) with a mixed solvent system of chlorobenzene (CB) and isopropanol (IPA). Based on CHEAI passivation, the CB/IPA mixed solvent system manipulates solvent polarity gradients to induce molecular self-assembly, constructing a uniform two-dimensional(2D) perovskite interfacial layer that enables effective defect passivation and rapid charge transport, thereby addressing this trade-off. This strategy achieves a power conversion efficiency (PCE) of 25.72% and a fill factor (FF) of 86.27%, the highest reported values for conventional two-step method-based triple-cation perovskite solar cells (PSCs). Moreover, it demonstrates effectiveness in systems with different passivating agents. This study provides a straightforward and effective approach to improving the efficiency and stability of PSCs.