Transient response of a bilayer organic electroluminescent diode: Experimental and theoretical study of electroluminescence onset

The experimental transient electroluminescence response of a bilayer organi c light-emitting diode reported here shows an initial overshoot when suffic ient direct current bias is superimposed to pulse excitation. Using a theor etical model giving the kinetic equations which govern the time evolution o f electrical fields, currents and charge densities in the device, we calcul ate transient response of light emission. The results show a good agreement with experiments and evidence the charge carriers accumulation occurring i n the region of organic-organic interface due to unipolar injection. Applic ation of periodic excitation indicates that a characteristic time of 300 ms is needed to recover the initial electrical equilibrium state. (C) 2001 Am erican Institute of Physics.