Time-resolved fluorescence studies and Monte Carlo simulations of relaxation dynamics of photoexcitations in a polyfluorene film

Time-resolved fluorescence spectroscopy is used to investigate relaxation o f electronic excitations in films of a pi -conjugated polyfluorene polymer in the ps time domain. Results are consistent with theoretical predictions based on a model for relaxation of the excitations by incoherent hopping be tween localized states through Forster type energy transfer with a Forster radius R-0 similar to 20 Angstrom. Excitons created by a photon with an ene rgy <2.92 eV are found to remain immobile during their lifetime. In additio n the measurements indicate that for excitation energies >2.94 eV additiona l relaxation processes, ascribed to ultrafast intrachain vibrational relaxa tion, are operative. (C) 2001 Elsevier Science B.V. All rights reserved.