Direct Lead‐Iodide Scaffold Engineering via Macrocyclic Dual‐Function Coordination Breaks the Efficiency‐Stability Gap in 2D Perovskite Solar Cells

Despite the enhanced environmental stability, 2D perovskites exhibit inferior optoelectronic performance compared to 3D counterparts, primarily due to voltage losses induced by phase dispersion and energy disorder. Here, a universal phase‐regulation strategy is presented that directly targets the quantum‐well‐defining lead‐iodide framework, bypassing conventional spacer‐cation‐based colloidal engineering. By incorporating a macrocyclic coordination molecule with dual functionality, dynamic coordination modulation and in situ lead immobilization are synchronously achieve: i) dynamic coordination and spatial confinement to guide colloidal self‐assembly, enabling controlled quantum‐well growth and nucleation via pre‐ordering solvation intermediate phase, and ii) selective chelation of free Pb 2 ⁺ ions through stable metal‐organic bonds, mitigating lead leakage during processing and operation. Colloidal chemistry and crystallization dynamics analyses reveal that macrocyclic reduces n ‐phase polydispersity at the colloidal stage, yielding films with homogeneous phase distribution and minimized energy disorder. This optimizes carrier transport and suppresses energy loss, achieving a record power conversion efficiency of 23.11% for 2D perovskite solar cells. This work establishes a generalizable paradigm for phase regulation in low‐dimensional perovskites, bridging the efficiency‐stability gap by targeting the lead‐iodide scaffold rather than peripheral components.