Photovoltaic performance of ruthenium complex dye associated with number and position of carboxyl groups on bipyridine ligands

A series of ruthenium complex dyes with different number and position of carboxyl groups on bipyridine ligands, such as Ru(4-carboxyl-4′-methyl-2,2′-bipyridine)(4,4′-dimethyl-2,2′- bipyridine)(NCS)₂ (denoted as Ru1A), Ru(4-carboxyl-4′-methyl-2,2′-bipyridine)₂(NCS)₂ (Ru11A), Ru(4,4′-dicarboxyl-2,2′-bipyridine)(4,4′-dimethyl-2,2′-bipyridine)(NCS)₂ (Ru2A), and Ru(4-carboxyl-4′-methyl-2,2′-bipyridine)(4,4′-dicarboxyl-2,2′-bipyridine) (NCS)₂ (Ru3A) were synthesized and compared with Ru(4,4′-dicarboxyl-2,2′-bipyridine)₂ (NCS)₂, commonly known as N3 dye for the adsorption behavior on the TiO₂ surface and photovoltaic properties of dye-sensitized solar cells. The experimental results show that the tilt angle of ruthenium dyes on the TiO₂ surface which is dependent on the number and position of their carboxyl groups strongly affected the photovoltaic performance. - Highlights: • Ruthenium dye with different number of carboxyl groups adsorbed on the TiO₂ with different tilt angle. • Ruthenium dye injected the electrons to the TiO₂ through the carboxyl groups. • Photocurrent of DSSC, increased with the number of carboxyl groups on the ruthenium dye