DSSC research and development

Discovered in 1993, the photovoltaic performance of N3 has been unmatched for eight years by virtually hundreds of other complexes that have been synthesised and tested. However, in 2001 the black dye tri(cyanato)-2,2 2 -terpyridyl-4,4 4 -tricarboxylate)Ru(II) achieved 10.4% AM 1.5 solar-to-power conversion efficiency in full sunlight (Nazeeruddin et al, 2001). Conversion efficiencies have meanwhile been improved further, the current record validated by an accredited laboratory being 11.1% (Chiba et al, 2006). 

The most important further gains to be expected in the near term will be in the short-circuit photocurrent. New rntheninm complexes showing increased optical cross-sections and capable of absorbing longer wavelengths are currently under development (Wang et al, 2005a). For example, Fig. 8.8 shows the structure of a new dye coded K-19, which exhibits enhanced absorption by virtue of its. -system. 

A feature that makes the DSSC particularly attractive for tandem cell application is that its optical transmission and short-circuit photocurrent can be readily adjusted by changing the film thickness, pore size, the nature of the dye and the dye loading. This, along with the ease of forming layered structures, for example by producing the 

For most of the common sensitisers, the rate constant for electron injection from the excited state of the dye to the conduction band of the Ti02 particles is in the 

While impressive progress has been made in the development of stable, nonvolatile electrolyte formulations, the conversion yields obtained with these systems are presently in the 7-10% range, below the 11.1% reached with volatile solvents. Future research efforts will be dedicated to bridging the performance gap between these systems. The focus will be on hole conductors and solvent-free electrolytes such as ionic liquids. The latter are a particularly attractive choice for the first commercial modules, owing to their high stability, negligible vapour pressure and excellent compatibility with the environment. 

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