COMMUNICATION www.rsc.org/pps | Photochemical & Photobiological Sciences Cyclometalated iridium(III)-sensitized titanium dioxide solar cells†

Ir(III) dyes used as sensitizers in dye-sensitized solar cells produced quantum yields approaching unity for conversion of absorbed photons to current under simulated air mass 1.0 sunlight, with current production resulting from ligand-to-ligand charge-transfer states, rather than the typical metal-to-ligand charge-transfer states in ruthenium-based cells. Dye-sensitized nanocrystalline TiO2 solar cells (DSSCs) have at-tracted attention because they use inexpensive absorber materials for the conversion of sunlight into electricity.1,2 Efficiencies in excess of 10%have been documented in “champion ” devices of this type.3 Although the quantum yield for photocurrent production is close to unity for light absorbed by the dye (typically>1.7–2.0 eV), the photovoltage is only 0.7–0.9 V under 1 sun air mass (AM) 1.0 illumination.3,4 Efficient sensitization has been achieved with a variety o