Transient electroluminescence under double rectangular voltage pulses in light-emitting devices based on Evans blue

Transient electroluminescence (EL) characteristics of light emitting devices fabricated with Evans blue have been studied. A sequence of two rectangular voltage pulses separated by a time delay has been applied. The voltage amplitude and the separation between the pulses have been varied, and EL intensity has been measured. These studies have helped us to understand the behaviour of the space charges accumulated at the interfaces of the active layer with two electrodes. The variation of EL intensity during the second pulse for different separation times gives information regarding the relaxation process of accumulated charges in the device. The EL under a square-wave ac voltage further supports the role of accumulated charge in device operation.