Abstract
Ruthenium(II) complexes [Ru(L
2)(NCS)
2] (K8) and [Ru(L)(L
9)(NCS)
2] (K9) (where L
=
4,4′-bis(carboxyvinyl)-2,2′-bipyridine and L
9
=
4,4′-dinonyl-2,2′-bipyridine) were synthesized and characterized by spectroscopic and electrochemical techniques. The performance of K8 and K9 complexes as charge transfer photosensitizers in nanocrystalline TiO
2-based solar cells was investigated. These complexes when anchored onto TiO
2 films exhibit very efficient sensitization yielding 75
±
5% incident photon-to-current efficiencies (IPCE) in the visible region using an electrolyte consisting of 0.6
M methyl-
N-butyl imidazolium iodide, 0.05
M iodine, 0.1
M LiI and 0.5
M
tert-butylpyridine in 50/50
(v/v) mixture of valeronitrile and acetonitrile. At one sun, the K8 complex gave a short circuit photocurrent density of 18
±
0.5
mA/cm
2, the open circuit voltage 640
±
50
mV and fill factor of 0.75
±
0.05, corresponding to an overall conversion efficiency of 8.64
±
0.5%. Under similar conditions, the K9-sensitized solar cell gave a photocurrent density of 16.5
±
0.5
mA/cm
2, 666
±
50
mV open circuit potential and 0.71
±
0.05 fill factor yielding 7.81%
±
0.6% efficiency.