title: Characterisation of a ruthenium bipyridyl dye showing a long-lived charge-separated state on TiO2 in the presence of I-/I3-.
abstract: The control of the loss mechanism in a dye sensitised solar cell (DSSC) via recombination of the injected electron with the oxidised dye was investigated by incorporating a redox-active ligand, 6,7-bis(methylthio)tetrathiafulvalene dithiolate (TTF(SMe)(2)), into a ruthenium bipyridyl dye. A series of dyes with general formula [Ru(4,4'-R-bpy)(2)(TTF(SMe)(2)], where R = H, CO(2)Et and CO(2)H, were synthesised and characterised using electrochemistry, absorption and emission spectroscopy, spectroelectrochemistry and hybrid-DFT calculations. In addition, the performance of the acid derivative in a DSSC was investigated using IV measurements, as well as transient absorption spectroscopy. These complexes showed significant TTF-ligand character to the HOMO orbital, as deduced by spectroelectrochemical, emission and computational studies. Upon adsorption of the acid derivative to TiO(2) a long-lived charge-separated state of 20 ms was observed via transient absorption spectroscopy. Despite this long-lived charge-separated state, the dye yielded extremely low DSSC efficiencies, attributed to the poor regeneration of the neutral dye by iodide. As a result, the complex forms a novel long-lived charge separated state that persists even under working solar cell electrolyte conditions.
authors.affiliation: School of Chemistry, University of Edinburgh, King's Buildings, Edinburgh, UK EH9 3JJ.
authors.forename: Keri L
authors.initials: KL
authors.lastname: McCall
authors.forename: Ana
authors.initials: A
authors.lastname: Morandeira
authors.forename: James
authors.initials: J
authors.lastname: Durrant
authors.forename: Lesley J
authors.initials: LJ
authors.lastname: Yellowlees
authors.forename: Neil
authors.initials: N
authors.lastname: Robertson