A TD-DFT investigation of ground and excited state properties in indoline dyes used for dye-sensitized solar cells

The ground and excited state properties of three indoline dyes, namely D102, D131 and D149, especially designed for dye sensitized solar cell (DSC) applications have been studied by the means of density functional theory (DFT) and time-dependent DFT (TD-DFT) and compared with experimental absorption and fluorescence spectra. By comparison, insight on the behavior of a related dye (D205) is also given. Beside the good agreement between the computed and experimental spectra further proving the accuracy of the method used, that is, a hybrid (here PBE0) exchange correlation functional in conjunction with a polarizable continuum solvent (PCM) model and a medium size basis set, the calculations allow new insights into the electronic structure of this family of indolines, and in particular the electronic and geometrical structure at the first excited state. Possible insights on the optimization of dyes for photovoltaics applications, as well as warnings on the extrapolation of isolated dye properties towards cells behavior are given.