Bathochromic shift induced by sulfur-containing anchoring groups of organic dyes for DSSC

Dye-sensitizer solar cells (DSSC) are currently considered one of the most promising alternatives to traditional silicon solar cells. The research activity in this field is mostly focused on the design and synthesis of new organic dyes with potential application in this kind of devices. The compounds developed in this work are based on a structure well known design where a donor group (D) and an acceptor group (A) are joined by a conjugate bridge (?). In particular, we focused our efforts on the modification of the acceptor group due to his double function: anchoring the dye on the semiconductor (TiO2) and withdrawing electrons in the excited state of the molecule. We focused on the change of the carboxylic function into the thiocarboxylic and in the dithiocarboxylic ones. The presence of a sulfur atom in the anchoring group shown innovative features such as red-shift of ?max and more generally, a broadening of the absorption spectrum, as predicted by TD-DFT analysis previously carried out. Such improvements against the benchmark (DF15) have been confirmed by UV-Vis and fluorescence analysis on the obtained compounds.