4,4′-Unsymmetrically substituted-2,2′-bipyridines: novel bidentate ligands on ruthenium(ii) [3 + 2 + 1] mixed ligand complexes for efficient sensitization of nanocrystalline TiO2 in dye solar cells†
Abstract
A series of five new ruthenium [3 + 2 + 1] complexes coded as MC107–MC111, with novel unsymmetrical bipyridines as ancillary ligands and terpyridine tricarboxylic acid as an anchoring ligand have been successfully synthesized and characterized by 1H NMR, 13C NMR and UV-Visible spectrometry. Improvement in the molar extinction coefficient of all these sensitizers was observed compared with reference standard N749 dye under comparable conditions. Among all the new sensitizers MC108 exhibited a maximum solar to electrical conversion efficiency of 5.573% (Jsc = 16.81 mA cm−2, Voc = 0.50 V. FF = 0.65) under standard global AM 1.5 G solar condition, when compared to the N749 dye with an efficiency of 6.29% (Jsc = 13.74 mA cm−2, Voc = 0.67 V. FF = 0.68) under similar fabrication and evaluation conditions. Density functional theory (DFT) and time-dependent DFT calculations are carried out for MC107–MC111 to understand their structural, electronic and photophysical properties.