Interfacial Rotational Constraint Govern Buried‐Interface Energetics for Inverted Perovskite Solar Cells

ABSTRACT Self‐assembled monolayers (SAMs) are critical for high‐efficiency inverted perovskite solar cells (PSCs), but their use is limited by incomplete coverage, weak oxide adhesion, solvent desorption, and poor wettability. These issues stem from a structural constraint: conventional SAMs anchor through a single monodentate “hinge,” whose rotation hinders dense packing, creates surface‐energy heterogeneity, and destabilizes bottom and buried interfaces. Here, we introduce a molecular‐interlock strategy by incorporating lactic acid (LA) to pair with Me‐4PACz to restrict this rotational freedom. The carboxyl group of LA forms an additional coordination with hydroxylated NiO x and simultaneously interacts with undercoordinated Pb‐I species at the buried perovskite interface, creating a dual‐anchor configuration that enhances SAM adhesion and structural rigidity. This interlocked SAM improves surface uniformity, increases wettability toward perovskite inks, suppresses PbI 2 ‐related defect formation, optimizes energy‐level alignment, and releases interfacial residual stress, enabling compact and pinhole‐free perovskite films. As a result, PSCs using Me‐4PACz (LA) achieve a PCE of 26.87% (certified 26.31%), maintain 98.8% of their initial output after 1000 h MPP tracking, and retain 90% efficiency after 1200 h ambient storage. Large‐area (47.84 cm 2 ) modules reach 23.18%, demonstrating the broad applicability of rotationally restricted, molecular‐interlocked SAMs for robust and efficient perovskite photovoltaics.