The multiple regeneration mechanisms in dye-sensitized solar cells (DSSC), with N3 (Ru(dcbpy)(2)(NCS)(2)) as dye and I-/I-3(-) as redox shuttle, have been studied by DFT methods. Our results show that different reaction pathways are possible within the same dye and the actual mechanism is controlled by the initial geometry of the dyeI complex. By considering the rapid interconversion between different N3I geometries, the reaction mechanism where N3I dissociates into neutral dye and l radical is preferred to the mechanism where N3I reacts with a second iodide. (C) 2013 Elsevier B.V. All rights reserved.