Aza-dipyrrinato ruthenium sensitizers for enhancement of Light-Harvesting ability of Dye-Sensitized solar cells

[Display omitted] •Three new aza-dipyrrinato ruthenium sensitizers AZA-BPY, AZA-BPY-NCS, and AZA-TER have been designed and synthesized.•Aza-dipyrrinato ancillary ligand showed better light-harvesting capability compared to the traditional dipyrrinato ligand.•We have observed the panchromatic absorption (250 nm to 1000 nm) in aza-dipyrrinato ruthenium sensitizers.•We successfully demonstrated the tuning of optical properties of sensitizer by tailoring of dipyrrinato ancillary ligands. Three new aza-dipyrrinato ruthenium sensitizers AZA-BPY, AZA-BPY-NCS, and AZA-TER, have been designed and successfully synthesized. We have studied the effect of aza-dipyrrinato ligands on the photo-physical and electrochemical properties. The aza-dipyrrinato ancillary ligand exhibited enhancement in the light-harvesting capability compared to the traditional dipyrrinato ligand by coordinating ruthenium metal. The strong σ-donor characteristic of the aza-dipyrrinato ligand showed more adequate properties: red-shift in the absorption extended into the NIR region ( ≈ 1000 nm), and redox potentials compared to our earlier reported dipyrrinato sensitizer (GS3), which are confirmed by the UV–Vis absorption spectroscopy and cyclic voltammetry. All the characteristics features shows that these dyes are a good sensitizer candidate for DSSCs.