Current–voltage characteristics of organic heterostructure devices with insulating spacer layers

• A device model for dark current-bias property of donor/spacer/acceptor planer heterostructure is proposed.
• The model can explain the different behaviors of current-bias curves as a function of spacer thickness.
• Relevant experimental data of current density-bias curves for different spacer thicknesses are also proposed and discussed.

The dark current density in donor/acceptor organic planar heterostructure devices at a given forward voltage bias can either increase or decrease when an insulating spacer layer is added between the donor and acceptor layers. The dominant current flow process in these systems involves the formation and subsequent recombination of interfacial exciplex states. If the exciplex recombination rate limits current flow, an insulating interface layer decreases the dark current. However, if the exciplex formation rate limits the current, an insulating interface layer may increase the dark current. We present a device model to describe this behavior, and we discuss relevant experimental data.

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