PULSED ELECTROLUMINESCENCE IN A PARA-HEXAPHENYL BASED HETEROSTRUCTUREDEVICE

We present the performance of an organic blue-light emitting device un der quasi-stationary pulsed conditions. The transient current and ligh t emission shows a fast initial response that is followed by a continu ous increase of the light output. This behaviour, which is observed on a millisecond timescale is attributed to the formation of a charge ac cumulation layer at the organic layer/cathode interface, together with field enhanced electron injection. Furthermore, it is shown that reve rse biasing the device prior to the actual driving pulse increases the external quantum efficiency, which results into an enhancement of lig ht emission up to 25% by virtue of depleting space charge carriers and charge-filled trap sites.