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Electroluminescence has been widely reported in large band gap insulating polymers under any kind of electrical stress, being ac, dc, impulse etc. but its significance is still the matter of debate. It was first investigated in the late seventies in divergent field experiments (i.e. using needle electrodes embedded in the material) as a precursor of electrical treeing. Later on in the nineties, uniform...
One of the unresolved questions in the EL spectrum of insulating materials in general is the occurrence of red emissions under AC electric field when using e.g. silver or gold as metal electrodes. Surface plasmons (SPs) effects and/or charge recombination on surface states have both been advocated as possible origins for such emissions. In this contribution, EL of 25μm Polyethylene 2, 6-Naphthalate...
Recently, a charge transport model allowing the description of electroluminescence in polyethylene films under AC stress has been developed. The fluid model incorporates bipolar charge injection/extraction, transport and recombination. The model has been very successful in explaining the time-dependence of EL under 50 Hz sinusoidal, triangular and square voltage waveforms. In this work we discuss...
This paper compares two models describing electroluminescence under AC stress in order to gain a better understanding on the interfacial processes, responsible for light emission. Simulated data is also compared with electroluminescence measurements for LDPE samples using three types of applied voltage waveforms: sinusoidal, triangular and square.
More than fifty years after the publication of the early work on electrical transport in disordered insulating solids, we are still unable to describe quantitatively the electrical response of these materials. During this period of time, concepts derived from semiconductor physics have been transposed to the case of insulating solids, and among them, to polymers. In spite of this, there is still no...
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...
The transient light emission from cellular polypropylene ferroelectrets subjected to high electric poling fields, both in high vacuum and at atmospheric pressure, was quantitatively measured and correlated with the piezoelectric d33 coefficient. The spectrum shows strong emission from the second positive system of molecular nitrogen and the first negative system of N2+.
Films of poly(ethylene naphthalate), polyethylene (either low density or cross-linked) and epoxy resins have been irradiated with electrons having kinetic energies of up to 10 keV, i.e. able to break bonds of the polymeric chains (featuring therefore hot electrons effects). The so-called cathodo-luminescence spectrum has been acquired for different electron energies. With the various materials tested,...
Epoxy resins have been used for long as the insulation of electrical systems. It is generally formulated with a dispersion of micro-fillers to improve thermal and mechanical properties. However, there are concerns on the possible influence of these fillers on the electric behavior, especially on the long term ageing under functional stresses. Defects (decohesion between matrix and fillers, macro and...
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