A phenylcarbazole functionalized ruthenium dye for efficient dye-sensitized solar cells

A new heteroleptic Ru(II) complex of [Ru(Hcpip)(Hdcbpy)(NCS)2] [N(C4H9)4]+ H2O {where Hcpip = 2-(4-(9H-carbazol-9-yl)phenyl)- 1H-imidazo[4,5-f] [1,10]phenanthroline, Hdcbpy = 4-carboxylic acid-40-carboxylate-2,20-bipyridine} has been synthesized and demonstrated to function as an efficient sensitizer for nanocrystalline TiO2-based dye-sensitized solar cell (DSSC). The DSSC based on this Ru(II) complex showed a short-circuit photocurrent density of 19.2 mA cm 2, an open-circuit photovoltage of 630 mV, a fill factor of 57.7%, corresponding to an overall light to electricity conversion efficiency of 6.98% under simulated solar light irradiation at 100 mW cm 2. This efficiency value is 2.81- and 1.08-fold efficiency values of 2.48% and 6.47% observed for carbazole-free parent complex [Ru(Hpip)(Hdcbpy)(NCS)2] [N(C4H9)4]+ H2O {where Hpip = 2-phenyl-1H-imidazo[4,5-f][1,10]phenanthroline}- and cis-bis(isothiocyanato) bis(4,40-dicarboxylic acid-2,20-bipyridine)ruthenium(II) N3-based solar cells respectively, under identical experimental conditions. The molecular structures and electronic properties of the Ru(II) complexes were also investigated by means of density functional theory calculations in an effort to understand the device performance observed. 2011 Elsevier Ltd. All rights reserved.