Stepwise assembly of amphiphilic ruthenium sensitizers and their applications in dye-sensitized solar cell

Abstract

A novel synthetic route for preparation of amphiphilic heteroleptic ruthenium(II) complexes of the type [Ru(H2dcbpy)Cl(cymene)]NO 3 (1) [Ru(H2dcbpy)(dmbpy)(NCS)2] (2), [Ru(H2dcbpy)(dhbpy)(NCS)2] (3) [Ru(H2dcbpy) (dnbpy)(NCS)2] (4) and [Ru(H2dcbpy)(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 μm 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 I2; 0.1 M LiI; 0.5 M tert-butyl pyridine in 1:1 acetonitrile + valeronitrile the films yielded a short circuit photocurrent density of 16±0.5 mA/cm2 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. © 2004 Elsevier B.V. All rights reserved.