Synthesis of novel ruthenium sensitizers and their application in dye-sensitized solar cells

Ruthenium(H) 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 L9 = 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 TiO2 based solar cells was investigated. These complexes when anchored onto TiO2 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. (c) 2005 Elsevier B.V. All rights reserved.