Effect of trap position on the electrical properties of unipolar organic semiconductor devices

We investigated the electrical properties of a unipolar organic device with traps that were intentionally inserted into a particular position in the device. Depending on their inserted position, the traps significantly alter the charge distribution and the resulting electric field as well as the charge transport behavior in the device. In particular, as the traps are situated closer to a charge-injection electrode, the band bending of a trap-containing organic layer occurs more strongly so that it effectively imposes a higher charge injection barrier. We propose an electrical model that fully accounts for the observed change in the electrical properties of the device with respect to the trap position.