Confinement of MACl guest in 2D ZIF-8 triggers interface and bulk passivation for efficient and UV-stable perovskite solar cells

The rational passivation of the defects at the buried interface plays a significant role in reducing energy loss and improving the photovoltaic performance of perovskite solar cells (PSCs). Herein, we have applied a metal-organic framework (MOF)-based host-guest system consisting of zeolitic imidazolate framework-8 (ZIF-8) nanosheets confined with methylammonium chloride (MACl) to modify the SnO2/perovskite interface. The MACl@ZIF-8 not only effectively reduces the oxygen vacancies on SnO2, but also binds with the uncoordinated Pb2+ and halogen ions at the bottom of the perovskite layer. Moreover, the loaded MACl guest plays the role of both crystalline seeds involved in the formation of ZIF-8@perovskite heterojunctions and organic cation vacancy passivators. Thus, the simultaneous passivation of the buried interface and bulk phase of the perovskite is realized, and the photovoltaic performance of devices is enhanced considerably with an optimal efficiency of 22.10%. The introduction of MACl@ZIF-8 also allows the device to achieve excellent moisture stability due to better crystallinity and fewer phase defects. In particular, the UV shielding characteristic of the imidazole ligands in ZIF-8 results in a significant increase in the UV resistance capability.