Transient Electroluminescence in the Light-Emitting Diodes of Poly(p-phenylene) Thin Film

Abstract

We have studied the temporal response of the electroluminescence (EL) emission in the lightemitting diodes fabricated with a vacuum-deposited poly (p-phenylene) (PPP) thin lm as an emissive layer sandwiched between indium-tin-oxide (ITO) and Al electrodes. Upon application of a rectangular driving voltage with a forward bias, we observed a time delay between the onset of the bias voltage pulse and the EL emission. The EL time delay results from the charge carrier transport towards the recombination zone. Since the hole mobility is much larger than the electron mobility in PPP, the EL delay time is the transit time for holes in PPP thin films. The hole mobility is estimated to be 1 10􀀀5 cm2/Vs in vacuum-deposited PPP films.