Energy transfer and excitation migration in a doped organic semiconductor

摘要

We have studied energy transfer to a dioxolane-substituted pentacene derivative, 6,14-bis-(triisopropylsilylethynyl)-1,3,9,11-tetraoxa-dicyclopenta[b,m]pentacene (TP-5), from tris(8-hydroxyquin-8-olinato) aluminum(III) (Alq_3) by steady state and time-resolved photoluminescence (PL) spectroscopy. The Foerster transfer radius is 27 A, calculated from the fluorescence spectrum of Alq_3 and the absorption spectrum of TP-5. We find that pentacene emission dominates the PL spectra of TP-5:Alq_3 guest-host films, even at concentrations where the typical guest separation is significantly larger than the Foerster transfer radius. Monte Carlo simulations of energy transfer to randomly dispersed guest molecules in the host matrix show that Foerster-type energy transfer cannot completely account for the PL dynamics of the guest and host. Exciton diffusion within the Alq_3 host followed by fluorescence of the host molecules or energy transfer to the guest explains the PL spectra and dynamics.