D–π–A system based on zinc porphyrin dyes for dye-sensitized solar cells: Combined experimental and DFT–TDDFT study

A series of four new porphyrin-furan dyads were designed and synthesized by having anchoring group either at meso-phenyl or pyrrole-β position of a zinc porphyrin based on donor–π–acceptor (D–π–A) approach. The porphyrin macrocycle acts as donor, furan hetero cycle acts as π-spacer and either cyanoacetic acid or malonic acid group acts as acceptor. These dyads were fully characterized by UV–Visible, 1H NMR, MALDI-MS and fluorescence spectroscopies and cyclic voltammetry. Both of the observed and TD-DFT simulated UV–Vis spectra has strong correlation which validate and confirm the synthesized dyads and theoretical method for this type of compounds. Both soret and Q-bands are red shifted in the case of pyrrole-β substituted dyads. The redox potentials of all four dyads are not altered in comparison with their individual constituents. The dyads were tested in dye sensitized solar cells and found pyrrole-β substituted zinc porphyrins are showing better performance in comparison with the corresponding meso-phenyl dyads. Optical band gap, Natural bonding, and Molecular bonding orbital (HOMO–LUMO) analysis are in favour of pyrrole-β substituted zinc porphyrins contrast to meso-phenyl dyads.