Breaking Electronic Insulation of Monocyclic Aromatic Spacers via Hydrazide‐Induced Orbital Coupling in Ruddlesden‐Popper Perovskites

ABSTRACT Ruddlesden–Popper perovskites are promising photovoltaic materials because their enhanced structural and environmental stability relative to their three‐dimensional counterparts. However, weak interactions between organic spacer and the adjacent inorganic framework often undermine structural stability and impede charge transport. Here, we demonstrate that the hydrazide‐based spacer, thiophene‐2‐hydrazide (ThCH), unexpectedly induces strong interlayer orbital coupling in 2D RP perovskites despite its monocyclic aromatic structure. It is found that the hydrazide group extends electronic conjugation and promotes orbital hybridization between ThCH and the adjacent inorganic framework, a phenomenon not observed in conventional single‐ring aromatic spacers. This effect is further verified by benzo hydrazide, which shares a similar structural motif. Beyond promoting electronic coupling, the hydrazide functionality enhances film formation, yielding enhanced crystallization uniformity and facilitating efficient charge transport. Consequently, ThCH‐based RP perovskite (nominal n = 4) devices achieve record efficiencies of 22.41% (certified 21.74%, 0.074 cm 2 ) for small‐area devices and 20.74% (certified 20.01%, 1.015 cm 2 ) for large‐area devices, the highest reported for quasi‐2D RP PSCs. This study establishes a molecular design strategy that uses multifunctional hydrazide modules to overcome the electronic insulation of single‐ring aromatic spacers, enabling robust and efficient RP PSCs.