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Electroluminescence from a surface layer of polytetrafluoroethylene (PTFE) has been investigated using a photomultiplier tube and an intensified charge-coupled device (ICCD) camera under ac or half rectified ac (HRAC) electric fields tangential to the polymer surface. The electroluminescence (EL) characteristics from the polymer surface layer showed a similarity to those from PTFE and other polymer films subjected to ac or HRAC electric fields in the normal direction to the surface. ICCD imaging of EL indicated a large area of EL activity where the EL intensity was maximum at the electrode edge and EL was still observable 2 mm from the electrode. The injection and transport of electrons and holes via surface states in the surface layer and the subsequent electron-hole recombination give rise to EL, strongly depending on the spatial distribution of the surface states. The injection length of charges can be estimated to be at least 2 mm from the electrode in the tangential direction to the surface.

Electroluminescence (EL) from HDPE (high-density polyethylene) films subjected to repetitive rectangular-shaped impulse voltages has been investigated at electric fields

EL (electroluminescence) in several polymeric materials was investigated in the electric field range < 90 kV/mm. We used polymeric films with semi-transparent gold electrodes: low-density polyethylene, polypropylene, polytetrafluoroethylene and polyvinylchloride. The EL characteristics were very low EL inception fields (2 to 20 kV/mm) which strongly depend on the material and very low energy photon emission (mainly in the red region of 1.6 to 1.8 eV). These results reveal that EL emission occurs predominantly in the metal-polymer interface region rather than in the bulk of the polymer at the applied field. We present a model of EL emission in the metal-polymer interface region to explain our results qualitatively. In this model, the mechanism of EL emission is the radiative recombination of the electrons and holes trapped at the surface states of the polymer, which causes photon emission in the red region. The EL inception field and EL intensity depend on the density of the surface states of the polymers.