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The interest in vertical organic transistors as a means to overcome the limitations of conventional organic field-effect transistors (OFETs) has been growing steadily in recent years. Current vertical architectures, however, often suffer from a lack of parameter control, as they are limited to certain materials and processing techniques, making a controlled shift of, e.g., the transistor threshold voltage difficult. In this contribution, we present a vertical OFET (VOFET) operating in the inversion regime. By varying the thickness or doping concentration of a p-doped layer in an otherwise n-type VOFET, we are able to shift the threshold voltage in a controlled manner from 1.61 V (for a normal n-type VOFET) to 4.83 V (for the highest doping concentration of 50 mol. %). Furthermore, it is found that low doping concentrations of 20 mol. % can improve the Off state of the VOFET through reduction of the source-drain leakage current.

The importance of O3 pulse duration for encapsulation of organic light emitting diodes (OLEDs) with ultra thin inorganic atomic layer deposited Al2O3 layers is demonstrated for deposition temperatures of 50 °C. X-ray reflectivity (XRR) measurements show that O3 pulse durations longer than 15 s produce dense and thin Al2O3 layers. Correspondingly, black spot growth is not observed in OLEDs encapsulated with such layers during 91 days of aging under ambient conditions. This implies that XRR can be used as a tool for process optimization of OLED encapsulation layers leading to devices with long lifetimes.