Regensburg 2004 – scientific programme
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SYOH: Organic and Hybrid Systems for Future Electronics
SYOH 5: Poster
SYOH 5.90: Poster
Thursday, March 11, 2004, 18:00–21:00, B
Origin of delayed fluorescence in conjugated polymers — •Dirk Hertel1 and Chan Im2 — 1Institute of Physical Chemistry, University of Cologne, Luxemburger Str. 116, 50939 Cologne, Germany — 2Max-Planck Institute for Polymer Research, Ackermannweg 10, 55021 Mainz, Germany
We report on measurements of phosphorescence (Ph) and delayed fluorescence (DF) in poly(2,7-(9,9-bis(2-ethylhexyl)fluorene)) (PF2/6) present as dilute solid solution as well as in bulk films. From combined experimental investigations of the time and intensity dependence of DF and Ph as well as the temperature dependence of DF we are able to show that DF in PF2/6 both in solution and film is dominated by triplet-triplet annihilation (TTA). As a consequence of the intra-chain diffusion and, hence, relaxation of triplets, the kinetics of the bimolecular reaction show a turn-over from dispersive to non-dispersive regime as borne out by the DF decay. This in accord with theoretical predictions of TTA in disordered solids.
The dominance of TTA as source of DF in PF2/6 films is in marked contrast to the DF in MeLPPP, although the chemical structures of the materials are similar. In MeLPPP geminate pair recombination is responsible for DF. In order to understand the relation between chemical structure and routes of DF generation we have investigated the delayed fluorescence on the electron-accepting poly(9,9-dioctylfluorene-co-benzothiadiazole) F8BT present as film and solid solution.