Synergistic Anion‐π Interaction With an Electron‐Deficient Porphyrin Stabilizes Perovskite for High‐Performance Printable Carbon‐Electrode Mesoscopic Solar Cells

ABSTRACT The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has progressed rapidly, but operational stability under light and thermal stresses remains a critical challenge, largely due to the migration of weakly bound iodide ions at the lattice terminations. Here, we introduce an electron‐deficient macrocycle, 5,10,15,20‐tetrakis(4‐nitrophenyl)porphyrin (TNPP), as a terminal ion stabilizer in printable carbon‐electrode mesoscopic PSCs (p‐MPSCs). The strongly electron‐withdrawing nitro groups create an electropositive cavity in TNPP, enabling synergistic anion‐π and hydrogen‐bonding interactions with the perovskite lattice. This dual interaction mechanism anchors terminal iodide ions and A‐site cations, effectively suppressing ion migration and subsequent perovskite decomposition under environmental stressors. Consequently, TNPP‐modified devices achieve a champion PCE of 21.38% alongside exceptional stability. They retain > 95% of their initial PCE after 2000 h in ambient air (50%–70% RH), > 90% after 1040 h at 85°C under inert atmosphere, and > 95% after 1200 h of maximum power point tracking (MPPT) at 55°C under continuous illumination. This work demonstrates a potent molecular design strategy for stabilizing the perovskite lattice through synergistic non‐covalent interactions.