FRET resonance energy transfer for dye-sensitizer solar cells (DSSC)

Förster resonance energy transfer (FRET) is based on dipole-dipole coupling between two different molecules or molecular fragments separated by a short distance, one of which is able to transfer its energy to the other by means of a non-radiative mechanism. The goal of this study is to demonstrate the physics of FRET effect between two bound organic fragments within the structure of an organic DSSC (Dye-Sensitized Solar Cell) sensitizer. In fact, if the light energy absorbed by the donor (or antenna) moiety gets transferred to the acceptor dye through FRET, it is possible to broaden the light absorption profile of the resulting device, possibly improving its performances. The right choice of the fragments is driven by the good overlap between the emission and the absorption spectra of the compounds. We examined the possibility of designing a new covalent antenna-dye system with a completely organic structure (Figure 1), connecting the two units with a "azide-alkyne cycloaddition" reaction at the end of our route. We selected a typical metal-free DSSC dye characterized by a D-A-?-A (Donor-Acceptor-?-spacer-Acceptor) architecture, while as the antenna we employed a benzothiadiazole scaffold decorated with thiophenes bearing different substituents. In this communication, we will report recent progresses on the synthesis of this new covalent construct, and on its spectroscopic characterization