Heterogeneous Nucleation and Enhanced Charge Transfer via Amorphous Metal-Organic Frameworks for Efficient and Stable Perovskite Solar Cells

The two-step sequential deposition method is considered a potential way for the large-scale manufacture of perovskite solar cells (PSCs) with high power conversion efficiency and reproducibility. However, the dense lead iodide (PbI2) film interferes with its full contact with organic solutions, resulting in an inadequate reaction at the interface. Herein, 2 kinds of metal-organic framework (MOF) are introduced, amorphous Ni-MOF-74 (amNi-MOF-74) and crystalline Zn-MOF-74 (crZn-MOF-74), into PbI2 for regulating crystallization. Compared to crZn-MOF-74, the incorporation of amNi-MOF-74 exhibited rapid nucleation, resulting in high-quality perovskite films with large grain size, low trap density, and enhanced charge transfer between the perovskite and charge transfer layers. Meanwhile, the content of unstable phase PbI2 left in perovskite films due to insufficient reaction is also reduced. The amNi-MOF-74 modified PSCs exhibited a champion power conversion efficiency of 24.17% with good humidity and thermal stability. The unencapsulated device maintains 90% of its initial efficiency after 1000 h storage in dark ambient conditions with approximate to 30% relative humidity. This strategy provides an effective approach for promoting the crystallization process of perovskite and fabricating efficient and stable PSCs. The inadequate crystallization of the two-step method has always puzzled researchers in perovskite solar cells. Two kinds of metal-organic frameworks to increase interface contact and reduce the nucleation crystallization barrier, resulting in a high-quality film are introduced. The modified perovskite solar cells exhibited a champion efficiency of 24.17% with good humidity and thermal stability. image