Preparation and application of new ruthenium(II) polypyridyl complexes as sensitizers for nanocrystalline TiO2

A series of Ru-(II) polypyridyl complexes, containing carboxylic- and sulph onic 'anchor' groups, were synthesized as sensitizers for nanocrystalline T iO2. Depending on number and type of ligands the sensitizers are divided in to three classes: tris-homoleptic complexes 1a-d, tris-heteroleptic complex es 2a-d and his-complexes 3a-f. The compounds were characterized and the ph otophysical and electrochemical properties were examined. These studies pro ved the suitability of 1a-3f as sensitizers for TiO2-based photoelectrochem ical 'Graetzel'-type solar cells. A comparison of the performance of the co mplexes 1a-3f in the cell relative to Ru(dcbpy)(2)(NCS)(2) 3d as internal s tandard for mean efficiency eta is presented, whereby Ru(dcphen)(2)(NCS)(2) 3f is shown to have an efficiency of eta(rel.)=62.3% relative to 3d. A pos sible reason for the particular efficiency of 3d as sensitizer is discussed . (C) 2000 Elsevier Science S.A. All rights reserved.