**4. Conclusions**

In this chapter, the most promising strategies toward lowering the operational voltage of organic FETs have been reviewed and discussed. This includes reducing the transistor threshold voltage and subthreshold swing. Apart from the semiconductor/insulator interface engineering that is not always straightforward, one either can employ high-k dielectric materials, reduce their thickness, or do both at the same time. The best performing dielectric materials in OFETs appear to be metal oxides. They intrinsically possess high dielectric constants and display low leakage currents. Also, they can be made ultra-thin (*d* ≤ 3 nm), and when deposited on plastic films, they are flexible and robust. However, depending on the intended applications, one can also use pristine organic, organic-inorganic hybrid, or highk/low-k multilayer dielectrics. Anodic oxidation is a very promising technique, which can considerably lower manufacturing costs of high-k materials and realize inexpensive low voltage OFETs and OFET-based circuits. It is a cheap, solutionbased deposition process that can be performed under ambient conditions. Since the anodization is a self-limiting and self-healing process, it can give pinhole-free, homogenous oxide layers that can be grown in ambient atmosphere at room temperature. As such, anodization has a high potential to be used in manufacturing of future OFET-based electronic devices and circuits.

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