Cyclometalated ruthenium chromophores for the dye-sensitized solar cell

The recent finding that cyclometalated Ru(II) chromophores can generate high power conversion efficiencies (eta) in the dye-sensitized solar cell (DSSC) has ushered in a new era of dye development. This class of dyestuff not only leaves open the opportunity to circumvent the labile monodentate NCS- groups that constitute conventional high performance dyes (e.g., [Ru(dcbpy)(2)(NCS)(2)]; dcbpy =4,4'-dicarboxy-2,2'-bipyridine (N-3) and derivatives thereof), but also offers unprecedented control of the frontier molecular orbitals for DSSC dyes. Indeed, complexes bearing aromatic cyclometalating hgands enable the manipulation of both the ground- and excited state reduction potentials through the judicious installation of substituents. This review outlines how the new and rapidly expanding class of Ru-based sensitizers bearing bidentate and tridentate cyclometalating ligands provide a conduit for potentially enhancing the stability and performance of the DSSC, gaining new insight into interfacial electron-transfer and dye regeneration processes, and utilizing new redox mediators in the DSSC. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.