Power Dependence of the Magnetic Field Effect on Triplet Fusion: A Quantitative Model.

Two strategies for improving solar energy efficiencies, triplet fusion and singlet fission, rely on the details of triplet-triplet interactions. In triplet fusion, there are several steps, each of which is a possible loss mechanism. In solution, the parameters describing triplet fusion collisions are difficult to inspect. Here we show that these parameters can be determined by examining the magnetic field dependence of triplet fusion upconversion. We show that there is a reduction of the magnetic field effect for perylene triplet fusion as the system moves from the quadratic to linear annihilation regimes with an increase in laser power. Our data are modeled with a small set of parameters that characterize the triplet fusion dynamics. These parameters are cross-validated with molecular dynamics simulations. This approach can be applied to both solution and solid state materials, providing a tool for screening potential annihilators for photon upconversion.