Dipole-Dipole Interaction Between A Fluorescent Dye and a Phosphorescent Dopant In Solid Thin Films: A Concentration and Excitation Intensity Study

摘要

Here we report on the long-range dipole-dipole Forster energy transfer between the fluorescent dye 4,4'-N,N'-dicarbazole-biphenyl (CBP) and the phosphorescent organ-ometallic complex fac tris(2-phenylpyridine) iridium(III) (Ir(ppy)_3). The study is carried out for both molecules dispersed in a polymer matrix forming a solid thin film. By studying the photoluminescence of these films with various concentrations of Ir(ppy)_3 (guest) and CBP (host) molecules at various optical excitation conditions and by comparing our experimental results with the predictions of a numerical model of the Foerster transfer process, we determined the total efficiency of energy transfer and a Forster interaction radius of 3 nm for the pair CBP:Ir(ppy)_3 without having to use time-resolved techniques. From this result, we discuss the optimum dopant to guest ratios in solid films of the pair CBP:Ir(ppy)_3 for maximum energy transfer following optical excitation.