Triplet-triplet annihilation upconversion kinetics of C 60 -Bodipy dyads as organic triplet photosensitizers.

Three new triplet photosensitizers consisting of a bodipy derivative and C60 moieties were synthesized for triplet-triplet annihilation upconversion of perylene. With the extension of the π-conjugated structure of the bodipy derivative, the three photosensitizers exhibited different absorption wavelengths, e.g. 517 nm for B-2, 532 nm for B-4, and 557 nm for B-6. The steady-state and transient absorption, steady-state fluorescence, and upconverted fluorescence emission were investigated to reveal step-by-step the dynamic processes of the above systems. The quantum yields of intramolecular energy transfer, intersystem crossing, and triplet-triplet energy transfer were measured. From the upconverted fluorescence emission spectra, the overall quantum yield of the triplet-triplet annihilation upconversion, ΦUC , was determined to be 5.80% for B-2, 7.95% for B-4, and 4.99% for B-6.