Molecular engineering on semiconductor surfaces:: design, synthesis and application of new efficient amphiphilic ruthenium photo sensitizers for nanocrystalline TiO2 solar cells

A new series of amphiphilic heteroleptic ruthenium(II) sensitizers [Ru(H(2)dcbpy)(dhbpy)(NCS)(2)] (CI), [Ru(H(2)dcbpy)(dchobpy)(NCS)(2)] (C2), [Ru(H(2)dcbpy)(mubpy)(NCS)(2)] (C3), [Ru(H(2)dcbpy)(dhabpy)(NCS)(2)] (C4) have been developed and fully characterized by UV-visible, emission. NMR and cyclic voltammetric studies (where mubpy 4-methyl-4'-perfluoro 1H, 1H, 2H, 2H, 3H, 3H undecyl-2,2'-bipyridine, dhabpy = 4-4'-dihexylamide-2,2'-bipyridine, dhbpy = 4-4'-dihexyl-2,2'-bipyridine, dchobpy = 4-4'-dicholesteryl-2,2'-bipyridine). The amphiphilic amide heteroleptic ruthenium(11) sensitizers, when anchored to nanocrystalline TiO2 films from ethanol solutions, achieve very efficient sensitization in the visible range yielding approximate to 80% incident photon-to-current conversion efficiency (IPCE) and display a short 2 circuit photocurrent density of 15 mA/cm(2) and an open circuit voltage of 0.75 V corresponding to an overall conversion efficiency of 7.4% under standard AM 1.5 sunlight. (C) 2003 Elsevier Science B.V. All rights reserved.