Multilateral Passivation Strategy in Post-Synthetic Flexible Metal-Organic Frameworks for Enhancing Perovskite Solar Cells

Thepreparation of MIL-88B-1,3-SO3H and MIL-88B-1,4-SO3H with multiple functional groups (-NH2,-NH-, and -SO3H) involved the utilizationof post-synthesis modification to introduce 1,3-propan sultone and1,4-butane sultone into the MIL-88B-NH2 framework, whichinteracted with uncoordinated Pb2+ in perovskite films,thereby passivating the inherent defects in the perovskite films andultimately leading to improved optoelectronic performance and long-termstability of perovskite solar cells. The photovoltaic performance of perovskite solar cellsis severelylimited by the innate defects of perovskite films. Metal-organicframework (MOF)-based additives with luxuriant skeleton structuresand tailored functional groups show a huge potential to solve theseproblems. Here, a multilateral passivation strategy is performed byintroducing two alkyl-sulfonic acid functionalized MOFs, MIL-88B-1,3-SO3H and MIL-88B-1,4-SO3H, respectively, obtainedfrom MIL-88B-NH2 through a post-synthetic process, forcoordinating the lead defects and inhibiting non-radiative recombination.The flexible MIL-88B-type frameworks endow both functionalized MOFswith excellent electrical conductivity and preferable carrier transportin the hole-transport materials. Compared with the original MIL-88B-NH2 and MIL-88B-1,4-SO3H, MIL-88B-1,3-SO3H exhibits optimal steric hindrance and multiple passivation groups(-NH2, -NH-, and -SO3H), achieving the champion doped device with an enhanced power conversionefficiency (PCE) of 22.44% and excellent stability, which maintains92.8% of the original PCE under ambient conditions (40% humidity and25 & DEG;C) for 1200 h.

Automated summary

The preparation of MIL-88B-1,3-SO3H and MIL-88B-1,4-SO3H with multiple functional groups significantly improved the optoelectronic performance and long-term stability of perovskite solar cells by passivating the inherent defects in the perovskite films using post-synthesis modification. This new approach shows great potential in solving the limitations of perovskite solar cells.