Two self-assemblies of Schiff base porphyrins to modify titanium dioxide electrodes for supramolecular solar cells

Abstract In this work, two Schiff base porphyrins have been successfully synthesized. The metal-ligand axial coordination assembling strategy has been used to organize two assemblies based on the two porphyrins appended isonicotinic acid ligands. Further, the assemblies were absorbed on the semiconducting TiO₂ electrode surfaces by the carboxylic groups of isonicotinic acid ligands, and their photovoltaic performances were performed under irradiance of 100 mW cm^-2 AM 1.5G sunlight. Photoelectrochemical studies show a significantly enhanced photovoltaic behavior for phenol-based zinc porphyrin assembly compared to pyridine-based zinc porphyrin assembly. The UV-Vis absorption, fluorescence spectra, molecular orbital patterns, and HOMO-LUMO energy gaps of the assemblies were also performed to further understand their photovoltaic features. In addition, the assembled modes of the assemblies immobilized on TiO₂ electrode surfaces were also verified by transmission electron microscopy.