Electroluminescence and high-field conduction in poly(ethylene-2, 6-naphthalate)

Electrical properties of poly(ethylene-2 6-naphthalate) (PEN) are investigated under d.c., a.c., and pulsed voltage with fields ranging from 0.1 up to several MV/cm. The onset of electroluminescence is correlated with an abrupt change in the d.c. current-voltage characteristics suggesting a carrier multiplication process controlled by impact ionisation. Pulsed voltage experiments show that light emission can also be due to recombination of injected charges with carriers of opposite polarity trapped in the polymer. Under a.c. voltage, there is a competition between these two light emitting processes as a function of the field magnitude. Emission spectra show distinct features under d.c. and a.c. excitation.