Cycloruthenated sensitizers: improving the dye-sensitized solar cell with classical inorganic chemistry principles

Abstract

A divergence from the conventional approach to chromophore design has led to the establishment of many exciting new benchmarks for the dye-sensitized solar cell (DSSC), including the first documented power conversion efficiency in excess of 12% at 1 sun illumination [Yella et al., Science 2011, 334, 629]. Paramount to these advances is the deviation from polypyridyl ruthenium dyes bearing NCS(-) ligands, such as [Ru(dcbpy)(2)(NCS)(2)] (N3; dcbpy = 4,4'-dicarboxy-2,2'-bipyridine). While metal-free and porphyrin dyes have demonstrated much promise, the discovery that the NCS(-) ligands of N3 can be replaced by anionic, chelating cyclometalating ligands without compromising device efficiencies has ushered in a new era of ruthenium dye development. A particularly appealing feature of this class of dyestuff is that they offer acute control of the frontier molecular orbitals to enable the precise attenuation of both the ground and excited state redox potentials through judicious chemical modification of the aryl ring. This Perspective summarizes very recent developments in the field, and demonstrates how the new and rapidly expanding class of Ru-based sensitizers provides a conduit for enhancing the performance (and potentially the stability) of the DSSC.

Sticking and patching: tuning and anchoring cyclometallated ruthenium(ii) complexes

“…The solution was decanted to separate a dark purple-red precipitate which was dried under reduced pressure. The solid was dissolved in MeCN (10 mL) and an excess of aqueous NH 4 [Ru(bpy) 2 [Ru(bpy) 2 [Ru(bpy) 2 …”

Substituent and Solvent Effects on the Electrochemical Properties and Intervalence Transfer in Asymmetric Mixed‐Valent Complexes Consisting of Cyclometalated Ruthenium and Ferrocene

“…The low Ru II/III potential (+ 0.74 V) of the cyclometalated ruthenium with a Ru À C bond is due to the electron-rich nature of the carbon anionic ligand. [27] In the near-infrared (NIR) region, an IVCT band at around 1780 nm, arising from charge transfer from the Ru II ion to the Fc + unit, is evident. To extend our work and to understand the effect of substituent and solvent effects on the electrochemical and IVCT properties, a series of complexes have been synthesized by changing the electronic nature of the auxiliary ligand around the ruthenium ion (Scheme 1).…”

Probing the excited state nature of coordination complexes with blended organic and inorganic chromophores using vibrational spectroscopy

“…Systematic studies of the effects of cyclometallation and TAA substituents on the energies of the dπ, π* and TAA π energy levels were performed ( Figure 18). [182,188] Cyclometallation could be used to tune the relative π* energy levels of the distal and proximal ligands, which also affects the dπ energy of Ru similarly to SCN -ligands. [182] Some of the dyes were tested in DSSCs.…”

“…[182,188] Cyclometallation could be used to tune the relative π* energy levels of the distal and proximal ligands, which also affects the dπ energy of Ru similarly to SCN -ligands. [182] Some of the dyes were tested in DSSCs. As expected, the best performing complex was cyclometallated such that the distal ligand had a lower π* energy than the proximal ligand.…”