Uniformly Anchored Dibenzothiophene‐Armed Self‐Assembled Molecule Regulates Perovskite Lattice for Efficient and Stable Solar Cells

The molecular aggregation of self‐assembled molecules (SAMs) and their weak anchoring to the perovskite layer result in interfacial non‑radiative recombination and perovskite degradation, significantly impeding improvements in the efficiency and stability of perovskite solar cells (PSCs). Here, we design a novel π ‐conjugated SAM, (4‐(3,6‐bis(dibenzo[b, d]thiophen‐2‐yl)‐9H‐carbazol‐9‐yl)butyl)phosphonic acid (4PADBT), to simultaneously address these challenges. The introduction of two non‐coplanar dibenzothiophene (DBT) units onto the conventional 4PACZ backbone creates a large dihedral angle (∼70°), which effectively suppresses molecular aggregation and promotes the formation of uniform and well‐ordered SAM films. Furthermore, the DBT groups act as a pair of anchoring arms, forming strong coordination bonds between sulfur (S) atoms and Pb 2+ ions at the buried interface. This uniform SAM layer and the strong interactions not only facilitate preferential (100) crystal orientation in the perovskite layer but also induce a lattice strain transition from tensile to compressive type, thereby effectively enhancing the structural stability and reducing defects. With these merits, the 4PADBT‐based device achieves a power conversion efficiency (PCE) of 26.25%, significantly higher than the 23.82% of the control 4PACZ device. Moreover, this design improves both thermal and operational stabilities, highlighting 4PADBT as a promising interfacial material for high‐efficiency and stable PSCs.