Triplet Sensitized Red-to-Blue Photon Upconversion

Sensitized red-to-blue upconversion with a record 0.8 eV anti-Stokes shift has been achieved utilizing platinum(II) tetraphenyltetrabenzoporphyrin (PtTPBP) as the triplet sensitizer and perylene as the energy acceptor/annihilator in deaerated benzene. Selective 635 nm excitation of PtTPBP results in the observation of perylene fluorescence centered at 451 nm. Stern−Volmer analysis of dynamic phosphorescence quenching of PtTPBP by perylene yields a triplet−triplet energy transfer quenching constant of 4.08 × 10 9 M −1 s −1 . Clear evidence for the subsequent triplet−triplet annihilation of 3 perylene* was afforded by the quadratic dependence of the integrated perylene fluorescence spectra with respect to incident 635 nm light power. The maximum upconversion quantum yield of perylene fluorescence under our sensitized excitation conditions is 0.0065 ± 0.0001, as ascertained by relative actinometry. The present chromophore combination was successfully translated into the solid state using a low glass transition temperature polyurethane host polymer, which produced upconverted photons for months when stored under ambient conditions.