Phthalocyanine-Based Multifunctional Additives for Efficient Defect Passivation in Perovskite Solar Cells

The long-term operational stability of perovskite solar cells (PSCs) is critically hindered by intrinsic ionic defects, particularly at grain boundaries and interfaces, which promote nonradiative recombination and accelerate performance degradation. In this study, we introduce a novel defect passivation strategy using functionalized phthalocyanine (Pc) derivatives incorporating both positively charged imidazolium (IZ) cations along with various counter-anions (I^-, TFSI^-, BF₄^-, and PF₆^-). These multifunctional additives simultaneously interact with under-coordinated Pb²⁺ sites and halide vacancies through Lewis acid-base interactions, thereby passivating defect states and reducing trap-assisted charge recombination. Density functional theory (DFT) calculations support the dual-site binding mechanism and reveal enhanced electronic coupling with the perovskite layer. Photophysical characterization reveals a significant reduction in nonradiative recombination, extended charge carrier lifetimes, and enhanced optoelectronic properties. The incorporation of Pc additives into PSCs leads to significant improvements in both photovoltaic performance and device durability. Notably, the BF₄^--modified Pc delivers a power conversion efficiency (PCE) exceeding 22% and exhibits superior stability under continuous illumination and thermal stress. This work emphasizes the capability of tailored Pc-based additives as an effective route to highly efficient and stable perovskite devices.