This work reports a theoretical study of the photovoltaic properties of a series of original conjugated metal-free organic dyes containing the triphenylamine (TPA) moiety. These compounds have recently been developed for dye sensitized solar cells (DSSCs). Our (TD)DFT-based procedure made it possible to get insights into the geometrical and electronic structures of the dyes and to unravel the structural modifications optimizing the properties of TPA-based DSSCs. In particular, we aimed at improving the electron injection process as well as the light harvesting efficiency of the dyes. On the other hand, molecular dynamic (MD) investigations of the kinetics of the regeneration step have been performed for both "classical" (CHCl3/I3 -/I-/Li+) and iodide imidazolium-based solvent-free electrolytes (DMII+/I-). The MD simulations helped to understand the regeneration mechanism for the solvent-free electrolyte: it combines the DMII+/DMII0 couple to the I3 -/I- redox system which acts as a "mediator". © 2010 American Chemical Society.