The fluorescence of guest-hot systems composed of an amorphous polymer matr
ix 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 excimer
s and that the excimer emission is strongly reduced as a function of irradi
ation time in the polymer matrix while no such effects were found for solut
ions of the chromophore in low molar mass solvents. The rate of change of s
teady state fluorescence depends on the polymer matric and the process is p
artially reversible in some guest-host systems. We tentatively attribute th
e effect to time dependent configurational changes taking place within the
chromophore-polymer matrix due to irradiation.