Photooxidation quantum yield efficiencies of naphthalene diimides under concentrated sun light in comparisons with perylene diimides

Thermal stabilities, solubilities redox potentials and photophysical parameters of 10 synthesized N-alkyl(aryl) derivatives of naphthalene diimides were studied for selecting the best derivatives at concentrated sun light experiments. N-aryl substitutions created better thermal stabilities than the N-alkyl substitution in naphthalene diimides. LUMO energy levels of NDIs, calculated from redox potentials, in the range of -3.55/-3.68 ev, proved that the naphthalene diimides can inject electrons efficiently in titania based organic dye sensitized solar cells. Fluorescence lifetimes of naphthalene diimides, tau(f) = 11-34 ps, are faster than that of perylene diimides, tau(f) = 4 ns. Calculated photooxidation quantum yields with a naphthalene diimide photosensitizer for the direct sun light oxidation reaction of anthracene is phi=0.014, and for the concentrated sun light of 10.2 sun is phi=0.044. In general photooxidation quantum yield efficiencies of naphthalene diimides under concentrated sun light irradiations are found to be higher with respect to the perylene dimide photosensitizers, due to production of both singlet oxygen and superoxide anion radical and enhancement of low wavelength solar radiation with aluminium surfaced mirror under concentrated sun light. (c) 2005 Elsevier B.V. All rights reserved.