Two self-assembled N-heterocyclic-substituted zinc porphyrins and isonicotinic acid dyads and their applications in supramolecular solar cells

In this work, two self-assembled N-heterocyclic-substituted zinc porphyrins and isonicotinic acid dyads formed by the coordination bonds of Zn-to-ligand, have been designed and organized. Further, the dyads were immobilized on the semiconducting TiO₂ electrode surfaces by the carboxylic groups of isonicotinic acid ligands, and their photovoltaic performances were measured under irradiance of 100 mW cm^-2 AM 1.5G sunlight. Photoelectrochemical studies reveal a significantly improved photovoltaic behavior for the dyad of tetrazole-based zinc porphyrin compared to the dyad with iminazole-based zinc porphyrin under the similar experimental conditions. The UV-Vis absorption, fluorescence spectra, molecular orbital (MO) patterns and HOMO-LUMO energy gaps of the dyads were studied to further reflect these photovoltaic features. In addition, the assembled modes of the dyads modified on TiO₂ electrode surfaces were also determined by transmission electron microscopy (TEM).