Unified model for the injection and transport of charge in organic diodes

This paper presents a unified model for charge injection and transport in organic or polymeric diodes. A special focus is placed on charge injection from the contacts, using existing models such as thermionic emission and tunnel injection. These are combined to produce a compact model that includes effects associated with oxidation/reduction reactions at the electrodes. Charges are formed at the electrodes by oxidation or reduction in a process governed by the Nernst equation, and these charges modulate the injection barrier. A current-voltage relationship for organic or polymeric diodes that incorporates these injection phenomena, as well as the charge transport by the drift mechanism, is presented and discussed. The voltage ranges in which these effects are dominant are estimated. Finally, the resulting current-voltage and current-temperature relations are used to explain published experimental data.