Time dependence of the steady state fluorescence in polymer guest-host systems

The fluorescence of guest-hot systems composed of an amorphous polymer matrix and various concentrations of selected chromophores is considered. Such systems are of interest for applications in organic light emitting diodes. The observation is that the fluorescence results predominantly from excimers and that the excimer emission is strongly reduced as a function of irradiation time in the polymer matrix while no such effects were found for solutions of the chromophore in low molar mass solvents. The rate of change of steady state fluorescence depends on the polymer matric and the process is partially reversible in some guest-host systems. We tentatively attribute the effect to time dependent configurational changes taking place within the chromophore-polymer matrix due to irradiation.