Effect of lithium perchlorate doping and prebiasing on electrical conduction of molecularly doped poly (N-vinylcarbazole) light emitting diode

The effect of lithium perchlorate (LiClO4) doping on the electrical propert ies of Light emitting diodes prepared by spin coating from the mixtures of Alq(3) and Coumarin 6 and poly (N-vinylcarbazole) was investigated in this study. We compared the current density-voltage (I-V) and the luminance-volt age (L-V) characteristics of the devices with and without LiClO4. It was fo und that the charge injection and the efficiency of the luminance were enha nced by doping a small amount of LiCLO4. We also investigated the effect of prebiasing on the current flows and the time response of current flows (I- t curves) during the prebiasing. The current flow in the film with LiClO4 d ecreased in the first several 10 a, and then gradually increased and reache d a constant value, whereas the current flow in the film without LiClO4 dec reased monotonously during the prebiasing. The charge injection was improve d by the prebiasing, and it was ascribed to the field enhancement effect du e to the: accumulation of ionic charges at the electrode/film interface.