Triplet exciton transfer mechanism between phosphorescent organic dye molecules

We fabricate simple, solution processed layers containing two kinds of phosphorescent, organic dyes in a poly(methyl methacrylate) (PMMA) matrix. After optical excitation, the close proximity of the emitter molecules with different triplet energies T1 causes a transfer of excitons from the more highly excited dye to the lower one. Optical characterization by photoluminescence (PL) and time resolved PL (TRPL) measurements leads to qualitative and quantitative investigations of the underlying exciton transfer principle. It can be shown that Dexter transfer is not able to describe the experimentally obtained data while an established model for exciton migration between fluorescent molecules, based on Förster theory, presents a consistent picture. Using this model, experimentally obtained values for the characteristic interaction distance R0 agree well with theoretical predictions by basic Förster theory.