New ruthenium complexes (Ru[3+2+1]) bearing π-extended 4-methylstyryl terpyridine and unsymmetrical bipyridine ligands for DSSC applications

•We synthesized two new ruthenium(II) [3+2+1] mixed ligand complexes.•The UV–Vis absorption extends up to 800 nm.•New sensitizers show high molar extinction coefficient compared to N749 dye.•Complex 1 exhibited high power conversion efficiency of 5.19%.

Two novel heteroleptic Ru[3+2+1] sensitizers, 1 and 2, with unsymmetrical bipyridine as ancillary ligand and electron donating 4-methylstyryl group in the anchoring π-extended terpyridyl ligand were synthesized and characterized. DFT studies reveal that the lowest unoccupied molecular orbital (LUMO) is distributed over the terpyridine. The two new sensitizers showed an improvement in the molar extinction coefficient compared to reference standard N749 dye. Among the two new sensitizers, 1 exhibited maximum solar to electric conversion efficiency (η) of 5.19% with short circuit current density of 14.032 mA cm−2, open circuit voltage of 0.520 V and fill factor of 0.712, under Air Mass (AM) 1.5 sunlight, while the reference N749 sensitized solar cell exhibited η-value of 6.44%.

Graphical abstractTwo novel ruthenium complexes (1 and 2) have been synthesized and characterized for application in dye sensitized solar cells (DSSCs). Sensitizer 1 is found to be more efficient compared to 2.Figure optionsDownload full-size imageDownload as PowerPoint slide