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

The experimental transient electroluminescence response of a bilayer organic light-emitting diode reported here shows an initial overshoot when sufficient direct current bias is superimposed to pulse excitation. Using a theoretical model giving the kinetic equations which govern the time evolution of electrical fields, currents and charge densities in the device, we calculate transient response of light emission. The results show a good agreement with experiments and evidence the charge carriers accumulation occurring in the region of organic–organic interface due to unipolar injection. Application of periodic excitation indicates that a characteristic time of 300 ms is needed to recover the initial electrical equilibrium state.