First-principles computational modeling of fluorescence resonance energy transfer in co-sensitized dye solar cells

TiO2 cosensitization by different dyes having complementary absorption represents an appealing strategy to obtain panchromatic sensitization in dye-sensitized solar cells. Fluorescence (Foster) resonance energy transfer (FRET) from an energy relay dye to a sensitizing dye, both grafted onto TiO2, was effectively shown to produce additional photocurrent (Hardin et al. J. Am. Chem. Soc. 2011, 133, 10662). Here we develop a realistic cosensitization model to provide a precise estimate of the geometrical parameters, which govern the FRET rate. The reliability of our model is fully confirmed by the quantitative reproduction of the experimental spectral shift in the naphtalocyanine absorption band and by the excellent agreement between the experimentally reported FRET rates. Our model provides a realistic picture of the cosensitized TiO2 interface and is capable, at the same time, of predicting the cosensitization mechanism and the associated FRET kinetics based on the sole photophysical characterization of the isolated donor/acceptor partners