Multifunctional Metal‐Organic Frameworks Capsules Modulate Reactivity of Lead Iodide toward Efficient Perovskite Solar Cells with UV Resistance

The two-step sequential deposition process is demonstrated as a reliable technology for the fabrication of efficient perovskite solar cells (PVSCs). However, the complete conversion of dense PbI₂ to perovskite in planar PVSCs is tough without mesoporous titanium dioxide as support. Herein, multifunctional capsules consisting of zeolitic imidazolate framework-8 (ZIF-8) encapsulant and formamidinium iodide (FAI) are introduced between tin oxide (SnO₂ ) and lead iodide (PbI₂ ) layer. Intriguingly, the capsule dopant interlayer benefits the formation of porous PbI₂ film due to the porous nanostructure of ZIF-8 that is favorable for the subsequent intercalation reaction. Furthermore, the constituent of the perovskite precursor in ZIF-8 pores can convert into the crystal nuclei of perovskite by reacting with PbI₂ first, thereby promoting further perovskite crystallization. Significantly, the incorporation of ZIF-8 can enhance the resistance of perovskite against UV illumination due to down-conversion effect. Consequently, the modified device achieves a champion power conversion efficiency (PCE) of 24.08% and displays enhanced UV stability, which can sustain 83% of its original PCE under 365 nm UV illumination for 300 h. Moreover, the unencapsulated device maintains 90% of initial PCE after 1500 h storage in dark ambient conditions with a relative humidity range of 50%-70%.