Crown Ether‐Based Co‐Self‐Assembled Monolayer Enhances the Interaction with Perovskite for High‐Performance Solar Cells

ABSTRACT The interface engineering of perovskite solar cells (PSCs), especially the optimization of the buried interface, is crucial for enhancing device efficiency and stability. To overcome the limitations of conventional self‐assembled hole transport monolayers (SAMs), such as insufficient film density, inadequate defect passivation, and suboptimal energy level alignment with perovskites, we designed and synthesized a novel multifunctional SAM functionalized with crown ether, named 15C5Ph‐4PACz, and utilized it in combination with Me‐4PACz to form a mixed SAM system. This mixed strategy ingeniously integrates hole transport (carbazole group), substrate anchoring (phosphonic acid group), and defect passivation (crown ether‐phenyl group) functions into one. The crown ether group can coordinate with uncoordinated Pb ²⁺ on the perovskite surface, significantly passivating interface defects and suppressing non‐radiative recombination. Furthermore, the mixed SAM optimizes interface energy level alignment, increases the work function and built‐in potential, and significantly enhances the interface charge extraction capability. As a result, the fabricated inverted devices achieved a power conversion efficiency of 25.39%. Additionally, the devices based on mixed SAM exhibit much improved stability. This work demonstrates a rational molecular design strategy for simultaneous interfacial defect passivation and efficient charge transport management, offering a promising pathway toward high‐performance and stable PSCs.