In this contribution, we describe the working principles of organic field effect transistors. To place it in context, we start with a brief description of some aspects of semiconductor field effect transistors. We then describe the standard structure and properties of laterally aligned field effect transistors and at the end, touch upon some properties of the newly developed vertically stacked field effect transistors.

Like most of the vertical transistors, the Patterned Source Vertical Organic Field Effect Transistor (PS-VOFET) does not exhibit saturation in the output characteristics. The importance of achieving a good saturation is demonstrated in a vertical organic light emitting transistor; however, this is critical for any application requiring the transistor to act as a current source. Thereafter, a 2D simulation tool was used to explain the physical mechanisms that prevent saturation as well as to suggest ways to overcome them. We found that by isolating the source facet from the drain-source electric field, the PS-VOFET architecture exhibits saturation. The process used for fabricating such saturation-enhancing structure is then described. The new device demonstrated close to an ideal saturation with only 1% change in the drain-source current over a 10 V change in the drain-source voltage. Published by AIP Publishing.

We demonstrate a low-temperature layer-by-layer formation of a metal-oxide-only (AlOx) gate dielectric to attain low-voltage operation of a self-assembly based vertical organic field effect transistor (VOFET). The AlOx deposition method results in uniform films characterized by high quality dielectric properties. Pin-hole free ultrathin layers with thicknesses ranging between 1.2 and 24 nm feature bulk dielectric permittivity, εAlOx, of 8.2, high breakdownfield (>8 MV cm(-1)), low leakage currents (<10(-7) A cm(-2) at 3MV cm(-1)), and high capacitance (up to 1 μF cm(-2)). We show the benefits of the tunable surface properties of the oxide-only dielectric utilized here, in facilitating the subsequent nanostructuring steps required to realize the VOFET patterned source electrode. Optimal wetting properties enable the directional block-copolymer based self-assembly patterning, as well as the formation of robust and continuous ultrathin metallic films. Supported by computer modeling, the vertical architecture and the methods demonstrated here offer a simple, low-cost, and free of expensive lithography route for the realization of low-voltage (VGS/DS≤3 V), low-power, and potentially high-frequency large-area electronics.

The application of orthogonal photolithography to micro-scale organic field effect transistors and complementary inverters on flexible substrate Appl.

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