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

Two strategies for improving solar energy efficiencies,tripletfusion and singlet fission, rely on the details of triplet-tripletinteractions. In triplet fusion, there are several steps, each ofwhich is a possible loss mechanism. In solution, the parameters describingtriplet fusion collisions are difficult to inspect. Here we show thatthese parameters can be determined by examining the magnetic fielddependence of triplet fusion upconversion. We show that there is areduction of the magnetic field effect for perylene triplet fusionas the system moves from the quadratic to linear annihilation regimeswith an increase in laser power. Our data are modeled with a smallset of parameters that characterize the triplet fusion dynamics. Theseparameters 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.