Transient electroluminescence from rubrene light-emitting diodes using double voltage pulse

Light-emitting diodes using a dye-insulating matrix blend of rubrene and arachidic acid have been fabricated using Langmuir–Blodgett film deposition technique. Transient electroluminescence (EL) measurements were performed by applying two consecutive square-wave voltage pulses separated by a short delay. This enabled us to study the effect of accumulated charges during the first pulse separated from that of the injected carriers, which are predominant during the second pulse. During the first voltage pulse, intrinsically accumulated charges recombine to generate an instantaneous EL peak, which is absent during the second pulse. A constant EL was observed during both the pulses. We also have observed an overshoot in EL in the falling edges of mainly negative voltage pulses.