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

Abstract

A new series of amphiphilic heteroleptic ruthenium(II) sensitizers [Ru(H2dcbpy)(dhbpy)(NCS)2] (C1), [Ru(H2dcbpy)(dchobpy)(NCS)2] (C2), [Ru(H2dcbpy)(mubpy)(NCS)2] (C3), [Ru(H2dcbpy)(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(II) sensitizers, when anchored to nanocrystalline TiO2 films from ethanol solutions, achieve very efficient sensitization in the visible range yielding ≈80% incident photon-to-current conversion efficiency (IPCE) and display a short circuit photocurrent density of 15 mA/cm2 and an open circuit voltage of 0.75 V corresponding to an overall conversion efficiency of 7.4% under standard AM 1.5 sunlight. © 2003 Elsevier Science B.V. All rights reserved.