Synergistic Bulk and Interface Passivation via Conjugated Ionic Additives Enables 26% Efficient PTAA‐Based Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) based on poly[bis(4‐phenyl) (2,4,6‐trimethylphenyl) amine] (PTAA) as the hole transport material offer excellent thermal stability but still suffer from open‐circuit voltage ( V _OC ) losses that limit their power conversion efficiency (PCE). These losses are primarily attributed to interfacial defects, energy level mismatches, and suboptimal contact with charge transport layers, which induce non‐radiative recombination. Here, a conjugated ionic additive designed to synergistically integrate interfacial engineering and bulk passivation is reported. The cationic π‐conjugated moiety localizes at grain boundaries and the perovskite/PTAA interface, enabling energy level tuning, defect passivation, and enhanced hole extraction, while the anionic counterpart preferentially resides at the buried perovskite/SnO ₂ interface, passivating interfacial defects and improving film quality. This dual‐site modulation yields high‐quality perovskite films with suppressed energetic disorder and improved charge extraction. As a result, n‐i‐p structured PSCs employing PTAA achieve PCEs of (25.73 ± 0.35)%, alongside a 15.17 cm ² mini‐module delivering (22.96 ± 0.61)% efficiencies. The devices exhibit outstanding stability, retaining 86% of the original PCE following 960 h of thermal aging at 85 °C in nitrogen. This work demonstrates that rationally designed conjugated ionic additives can simultaneously optimize bulk and interfacial properties, offering a viable route toward high‐efficiency, stable PSCs compatible with scalable manufacturing.