Delayed electroluminescence via triplet-triplet annihilation in light emitting diodes based on poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene]

A spectroscopically resolved delayed electrofluorescence is observed from poly[2-methoxy-5-(2(')-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) thin film at low temperature. From the measurements of the delayed fluorescence intensities at a particular delay time as well as the decay kinetics of the delayed fluorescence spectra at different temperatures, we conclude that the delayed fluorescence is generated via triplet-triplet annihilation. It is suggested that the triplet state of MEH-PPV thin film has a lifetime much shorter than that of polyfluorene thin film, which is consistent with the triplet energies of these polymers. (C) 2003 American Institute of Physics.