Model for energy transfer in polymer/dye blends based on point-surface dipole interaction

We report a new model for the Forster energy transfer in blends of Nile Red dye in poly-(9,9-dioctylfluorene) (PFO). We base our discussion on the possible arrangement of the dye molecules distributed in domains surrounded by polymer. These geometric considerations lead to a R -3 functional dependence for the energy transfer, different from the R -6 deduced by Forster for pointlike dipole-dipole interaction. The experimental value found for the Forster radius, namely 3.2 nm, is in good agreement with 3.6 nm obtained from the spectral overlap of donor emission and acceptor absorption.