MOF-808-Modified TiO ₂ /Perovskite Interfaces for Enhanced Efficiency and Stability in Perovskite Solar Cells

Interfacial defect states at the TiO 2 /perovskite junction significantly limit charge extraction and accelerate degradation in mesoscopic perovskite solar cells. Here, we investigate zirconium-based MOF-808 as a chemically active interfacial modifier employing two integration strategies: dispersion within the mesoporous TiO 2 scaffold and insertion as a discrete interlayer. The Zr 6 –oxo clusters provide Lewis acidic coordination sites capable of interacting with under-coordinated Pb 2+ , while carboxylate ligands mitigate halide vacancy defects, collectively suppressing trap-assisted recombination. Structural and spectroscopic analyses reveal improved interfacial contact and reduced non-radiative recombination, consistent with enhanced photoluminescence quantum yield and modified carrier lifetimes. Device measurements show that MOF incorporation increases power conversion efficiency from 17.8% (reference) to 20.1%, with further enhancement to 22.5% upon additional organic ammonium surface passivation. Moreover, MOF-modified devices exhibit improved operational and UV stability, attributed to reduced TiO 2 photocatalytic activity and defect-mediated degradation pathways. These findings establish MOF-808 as an effective coordination-driven interfacial material for controlling recombination kinetics and stabilizing TiO 2 /perovskite interfaces.