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.

Four new porphyrin based sensitizers have been synthesized with furan hetero aromatic ring between the porphyrin macrocycle and anchoring group either at meso-phenylor at pyrrole-β position of porphyrin. The porphyrin macrocycle acts as donor, furan hertero cycle acts as π-spacer and either cyanoacetic acid or malonic acid group acts as acceptor. The furan hetero aromatic ring at meso or β position can change the charge injection properties in dye sensitized solar cells. The DFT modelling to find HOMO and LUMO level for foreign at different positions has been studied and verified with experimental techniques.Figure optionsDownload as PowerPoint slide