Excitation energy migration in highly emissive semiconducting polymers

The process of excitation energy migration (EEM) in conjugated polymers, which is relevant both for light emitting diodes and laser applications, is probed by doping the blue light emitting methyl-substituted ladder-type poly(para-phenylene) with small concentrations of a highly fluorescent π-conjugated macromolecule. The experimentally attained temperature and concentration dependence of the steady state photoluminescence is modeled and discussed by means of a two-step EEM process: (1) a thermally activated migration within the host and (2) transfer from the host to the guest. In particular we show that a Förster-type mechanism alone cannot account for the experimental facts in such a guest host system.