Field and electron beam-induced luminescence phenomena in polypropylene thin films

Abstract

Field-induced luminescence of insulating polymers is an exciting field of research. Being intrinsically related with the high-field electronic properties of the material, it provides a way to investigate electrical ageing and breakdown processes. It is particularly suited for those materials used in high field applications, e.g. thin films of polypropylene in capacitors. One of the puzzling aspects of electroluminescence in wide band gap polymers is that the emission spectra are only reproduced under electron beam irradiation. In this communication, we report for the first time the field and electron beam induced luminescence in polypropylene films. Measurements were performed on 17 mthick bi-oriented polypropylene films. The home-designed electron gun provides electrons of up to 10 keV in energies. Emission spectra acquired for different beam energies are compared to the electroluminescence spectra obtained under AC stress for fields in the range 150-300 kV/mm. The nature of the excitation process in field and electron beam-induced luminescence is discussed together with the nature of emitting species and their significance for ageing study.

Combined-PSD and LIMM Measurements for Traps Characterization in BoPP Thin Films

“…4) of this peak shows two contributions, located at 229 and 204 nm, in agreement with earlier work [3]. These two contributions have to be correlated with the peaks observed in the absorption spectrum [9] of BoPP, that shows an absorption maximum at 200 nm and a first shoulder at 230 nm, typical of π→π* transitions in C=C double bonds. A second shoulder at 280 nm is rather due to the n→π* transition in carbonyl compounds.…”

“…A first peak with a maximum located at 397 nm is recorded in both cases. This peak is relatively broad (spreading from 480 nm to 360 nm with a FWHM of 50 nm) and does not correspond to known absorption band in BoPP investigated herein [9]. Either it can correspond to additives that could efficiently trap charges, or possibly to localized states formed under the effect of space charge [10].…”

“…A second shoulder at 280 nm is rather due to the n→π* transition in carbonyl compounds. These two wavelengths (230 and 280 nm) are those providing maximum photoluminescence in polyolefins [9]. Fig.…”