Comparison between photo-, cathodo-, and electro-luminescencespectra of polyethylene naphthalate films and relationship withelectrical aging

摘要

This work is a contribution to the identification of the spectralcomponents observed in the electroluminescence (EL) of insulatingpolymers. The approach aims at improving our current understanding ofthe nature of the interactions between electrical charges and the hostmaterial. In previous studies of poly(ethylene 2,6-naphthalate)-PEN, wehave shown that some spectral features of the light emitted under highfield could be associated with polymer degradation since they are notcharacteristic of the photophysical behavior of the material as probedby using mild UV-photons in photoluminescence experiments. So long asthe nature of the degradation mechanism is not identified, support tothis hypothesis can be brought considering other sources of excitationof the material that are likely to produce significant chemicaldegradation. Cathodoluminescence has been used in this respect, and acomparison between electro-, photo-, and cathodo-luminescence spectra isproposed. Some features of the EL spectrum that cannot be interpreted onthe basis of the photoluminescence spectrum are present in thecathodoluminescence spectrum. Consideration of the excitation mechanismsin the three kinds of experiment gives conclusive evidence of materialdegradation signatures in the EL spectrum