Degradation kinetics of the spectral emission in polyfluorene light-emitting electro-chemical cells and diodes

We have studied the well known spectral shift of polyfluorene blue light emitters, using either electrochemical cells or conventional organic light emitting diodes. From the recording of the electroluminescence spectra as a function of "stress" time, we conclude that the degradation mainly depends on the number of electrons which have passed through the conducting polymer, rather than on the hole current magnitude or the dissipated power.