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).