Ultrathin Self-Assembly Two-Dimensional Metal–Organic Framework Films as Hole Transport Layers in Ideal-Bandgap Perovskite Solar Cells

Two-dimensional conjugated metal–organic framework (2D c-MOF) Cu3(HHTT)2 (2,3,7,8,12,13-hexahydroxytetraazanaphthotetraphene, HHTT) is found to be an ideal hole transport material for Pb–Sn perovskite solar cells (PSCs) for the first time. 2D c-MOF films are conveniently prepared by a self-assembly deposition method and used in ideal-bandgap Pb–Sn mixed PSCs. The ultrasmooth surface of the Cu3(HHTT)2 film can facilitate perovskite growth and enable defect passivation on the perovskite surface. The self-assembly approach is suitable for preparing large-area films conformally on a substrate, promising the application of the film in large-area devices. Encouragingly, an efficiency over 22% is obtained from ideal-bandgap PSCs. Moreover, an efficiency of 19.86% for large-area ideal-bandgap PSCs is achieved from devices with an area of 1 cm2. This work demonstrates that 2D c-MOFs are promising charge transport materials for high-efficiency and large-area PSCs.