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

Abstract

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 TiO₂ film, which in turn resulted in no changes in the photovoltage.