A Multidentate Coordination Complex-Based Self-Assembled Monolayer Stabilizes Perovskite Interface

Self-assembled monolayers (SAMs) have emerged as promising hole-selective contacts for buried-interface engineering in inverted perovskite photovoltaics. However, most reported SAMs rely on a single phosphonic-acid anchoring group, which is prone to desorption during device fabrication and operation. In addition, their limited affinity for perovskite precursors often leads to poor wettability and non-ideal interfacial film formation. Here, we report a multidentate Fe(III) porphyrin complex as a co-SAM component that simultaneously reinforces substrate anchoring and promotes interfacial coupling with the perovskite, thereby stabilizing the buried interface. The four phosphonic-acid groups on porphyrin enable robust tetradentate chelation with the oxide substrate, increasing the adsorption energy by more than threefold. Meanwhile, the Fe center stabilizes the axial chloride ligand, which interacts with perovskite precursor, increases the apparent surface energy by ∼30%, and reduces the contact angle by ∼40%, thereby promoting high-quality perovskite crystallization. As a result, small-area devices achieve a power conversion efficiency of 27.06% (certified 26.82%), while perovskite modules deliver 24.1% efficiency over a 21.54 cm² aperture area, together with substantially improved operational stability. These results establish coordination-complex-based SAMs as an effective platform for stabilizing buried interfaces in perovskite photovoltaics.