Photophysical properties of new cyclometalated ruthenium complexes and their use in dye sensitized solar cells.

A new class of cyclometalated ruthenium complexes, Ru(C^N^N')(N^N'^N'')·Cl where N^N'^N'' = 4,4',4''-tricarboxy-2,2':6',2''-terpyridine and C^N^N' = substituted 6-phenyl-2,2'-bipyridine, for Dye Sensitized Solar Cells (DSSCs) is proposed. We have investigated the effect of different substituents (R = COOH, thiophen-2-yl, F and OCH(3)) on the ancillary C^N^N' ligand on the photophysical properties and performance of the six different cyclometalated ruthenium complexes in DSSCs. Using an ionic liquid based electrolyte, efficiencies up to η = 3.06% have been attained under 1 sun irradiation. Moreover, the T66 based DSSC exhibited a good stability under 1000 W m(2) light soaking at 60 °C for 24 days, retaining 92.8% of its initial efficiency.

Enhancement of photocurrent in dye sensitized solar cells incorporating a cyclometalated ruthenium complex with cuprous iodide as an electrolyte additive.

A new cyclometalated ruthenium complex, [Ru(6'-phenyl-4'-thiophen-2-yl-[2,2']bipyridinyl-4-carboxylic acid)(4,4',4''-tricarboxy- 2,2':6',2''-terpyridine)]Cl, for Dye Sensitized Solar Cells (DSSCs) is proposed. We have investigated the use of cuprous iodide (CuI) as an electrolyte additive, which in turn has shown photocurrent enhancements of more than 25% in our dye based cells. Using an ionic liquid based electrolyte, an efficiency of η = 5.7% has been accomplished under 1 sun irradiation. The origin of this photocurrent enhancement upon the CuI addition was studied by means of impedance spectroscopy and cyclic voltammetry under dark conditions. The reason behind such a photocurrent enhancement is attributed to an electrocatalytic effect of the CuI on the regeneration of the oxidized dye. Furthermore, the CuI addition did not affect the recombination processes between the injected electrons and the electrolyte nor the electron lifetime in the semiconductor TiO(2) film, which in turn resulted in no changes in the photovoltage.

Re-evaluation of recombination losses in dye-sensitized cells: the failure of dynamic relaxation methods to correctly predict diffusion length in nanoporous photoelectrodes.

Photocurrents generated by thick, strongly absorbing, dye-sensitized cells were reduced when the electrolyte iodine concentration was increased. Electron diffusion lengths measured using common transient techniques (L(n)) were at least two times higher than diffusion lengths measured at steady state (L(IPCE)). Charge collection efficiency calculated using L(n) seriously overpredicted photocurrent, while L(IPCE) correctly predicted photocurrent. This has implications for optimizing cell design.