Evidence of hot electron-induced chemical degradation in electroluminescence spectra of insulating polymers

Unlike semi-conducting organics, insulating polymers exhibit electroluminescence features that cannot be interpreted on the basis of the photo physical properties of the material. In particular, it is shown that the spectral components observed in electroluminescence in three different classes of insulating polymers -polyolefin, polyester and epoxy, can only be reproduced when the material is irradiated by an electron beam. This shows that hot electron impact is a driving process in electroluminescence and that the excited states decay route goes along the chemical pathway ending with molecular fragmentation. The results allow to associate electroluminescence and electrical degradation in an implicit scheme, opening the way for defining safety limits in terms of electric stresses applied to a material for a given application.