Synthesis of novel cyanine-fullerene dyads for photovoltaic devices

Two novel cyanine-fullerene dyads have been synthesized by means of the Prato reaction from the corresponding cyanine-aldehyde, N-methylglycine and C60. As well as a thorough characterization using MS-TOF, 1H-NMR, 13C-NMR and elemental analysis, the optical and electrochemical properties of these two dyads were investigated. The fluorescence of the cyanine-fullerene dyads was quenched efficiently as compared to the pristine cyanine, which we have attributed to photo-induced electron transfer from the cyanine to C60. The redox potentials obtained by cyclic voltammetry provide evidence that this electron transfer is energetically favorable. Single and double layer photovoltaic devices were fabricated to evaluate the photovoltaic properties of the dyad. The energetic conversion efficiency of the double layer device exceeds 0.1% under 3.1 mW cm-2 white light irradiation. The results show that cyanine-fullerene dyads are promising materials for photovoltaic devices