Vertical organic light-emitting transistor showing a high current on/off ratio through dielectric encapsulation for the effective charge pathway

We demonstrate a vertical organic light emitting transistor (VOLET) showing a high current on/off ratio through dielectric encapsulation of a finger-like source electrode, which is placed between the bottom gate electrode and the top drain electrode. In such a VOLET configuration, the charge transport occurs largely from the source electrode to an underlying organic semiconductor (OSC) layer through the interface between the OSC and the gate insulator. Accordingly, the current leakage is greatly reduced and the transistor-type switching behavior with a high on/off current ratio is achieved. The on/off current ratio of our VOLET is about 100 times higher than that of an existing VOLET with no dielectric encapsulation. Numerical simulations of the spatial distributions of the charge densities and the charge pathways performed in the two different VOLET configurations are in good agreement with the experimental results. Our dielectric encapsulation approach will provide a versatile method for developing a new class of high-performance OLET displays.