DSSC: a Synthetic Approach for FRET Increasing LHE of Dyes

Dye-Sensitized Solar Cells (DSSC) are photovoltaic devices where the photoactive compound is a dye molecule. Different kinds of dyes have been investigated in order to increase solar cell efficiency. Our group has focused its attention on D-pi-A organic dyes characterized by a common structural motif: an electron rich donor (D) linked to an electron poor acceptor (A) through a conjugated spacer. Such structure allows intramolecular charge transfer from Donor to Acceptor. Light Harvesting Efficiency (LHE) is a critical feature for dyes aimed at solar cells application. The design and synthesis of compounds with high molar extinction coefficient in a large range of wavelengths can result challenging. The aim of this work has been to design a photosensitizer capable to exploit Förster Resonance Energy Transfer (FRET) between an antenna and a D-pi-A dye, to increase the overall LHE. The antenna fluorescence spectra should overlap the absorption spectra of dyes (>30%) and be spatially adjacent to the chromophore (max 100 Å). A model dye was coupled to a series of fluorescents antennas, using the Cu(I) azido-alkyne coupling (CuAAC) click reaction as a versatile synthetic tool. The methodology might allow the preparation of libraries of dyes coupled with antennas to measure the LHE enhancement due to FRET effect.