van der Waals Epitaxial Growth of 2D Metal-Porphyrin Framework Derived Thin Films for Dye-Sensitized Solar Cells

In this work, monolithic, crystalline, porous, and oriented porphyrin thin films are grown using a novel van der Waals layer-by-layer (lbl) epitaxial growth protocol, yielding an unusual AB-stacking motif of these interesting macrocycles units. Subsequently, these surface-mounted metal-organic frameworks (SURMOFs) are transformed by thermal treatment to yield well-performing counter electrodes (CEs) for dye-sensitized solar cells. During this calcination, the heterocyclic macrocycles are metalated, yielding compact, homogeneous, and very stable metalloporphyrin thin films (ZnTCPP-C) with excellent CE performance. For thin films fabricated using three lbl cycles (thickness approximate to 17 nm), the power conversion efficiency is found to amount to 5.63%, making it a promising candidate to replace Pt CE (6.72%). Such calcined SURMOFs carry huge potential for fabricating electronic and photovoltaic devices.