Stepwise Assembly of Amphiphilic Ruthenium Sensitizers and their Applications in Dye Sensitized Solar Cell

A novel synthetic route for preparation of amphiphilic heteroleptic ruthenium(II) complexes of the type [Ru(H(2)dcbpy)Cl(cymene)]NO3 (1) [Ru(H(2)dcbpy)(dmbpy)(NCS)(2)] (2), [Ru(H(2)dcbpy)(dhbpy)(NCS)(2)] (3) [Ru(H(2)dcbpy)(dnbpy)(NCS)(2)] (4) and [Ru(H(2)dcbpy)(dtdbpy)(NCS)(2)] (5) have been developed starting from dichloro(p-cymene)ruthenium(II) dimer. The performance of these complexes as charge-transfer photosensitizers in nanocrystalline TiO2-based solar cells was studied. When anchored complexes 2-5 onto a 12 + 4 mum thick nanocrystalline TiO2 films achieve very efficient sensitization over 85 +/- 5% incident photon-to-current efficiencies (IPCEs) in the visible region. Under standard AM 1.5 sunlight, using an electrolyte consisting of 0.6 M BMII; 0.05 M I-2; 0.1 M Lil; 0.5 M tert-butyl pyridine in 1:1 acetonitrile + valeronitrile the films yielded a short circuit photocurrent density of 16 +/- 0.5 mA/cm(2) and the open circuit voltage was 700 +/- 50 mV and a fill factor of 0.75 +/- 0.05, corresponding to an overall conversion efficiency of 8.6%. Solar cells based on amphiphilic sensitizers show remarkable stability under both thermal stress and light soaking matching the durability criteria applied to silicon solar cells for outdoor applications.