Interface Molecular Locking Synergized with Self‐Assembled Monolayers for Efficient Perovskite Solar Cells

Abstract The uniformity of self‐assembled monolayers (SAMs) and the interfacial defects in perovskite films significantly affect the performance of inverted perovskite solar cells (IPSCs). Herein, we develop an innovative interface molecular locking (IML) strategy synergized with SAMs to enhance the properties of buried interface. Specifically, two SAMs—(4‐(3,6‐dimethoxy‐9H‐carbazol‐9‐yl)phenyl)phosphonic acid (MeO‐PhPACz) and 5‐indoleboronic acid (5‐IBA)—are employed to combine their advantages and form an enhanced SAM (E‐SAM). Due to the strong π–π interactions between MeO‐PhPACz and 5‐IBA, the E‐SAM exhibits a denser and more uniform morphological coverage. Introducing thiabendazole (TBZ) additive into the perovskite precursor further ameliorates the buried interface properties through its self‐assembly behavior, owing to its large molecular dipole moment and strong interactions with the E‐SAM. This strategy not only achieves favorable energy level alignment but also improves the crystallinity and reduces the trap density of perovskite films, thereby significantly enhancing hole extraction and suppressing non‐radiative recombination. Consequently, both (FA 0.95 MA 0.05 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.05 ) 3 and FA 0.95 Cs 0.05 PbI 3 ‐based IPSCs achieve high efficiencies exceeding 26.0%, along with significantly enhanced stability. Notably, (FA 0.95 MA 0.05 ) 0.95 Cs 0.05 Pb(I 0.95 Br 0.05 ) 3 solar cells deliver a high voltage of 1.21 V, one of the highest reported among IPSCs with a 1.56 eV bandgap. Our findings provide unique insights into achieving high‐performance IPSCs by synergistically engineering buried interface.