Performance and parameter variation of flexible organic thin film transistors in multicomponent organic sensors

Here we report on the fabrication and detailed characterization of flexible low-voltage organic thin-film transistors directly integrated with pyro-and piezoelectric sensors. The functional layer of the capacitive sensors is a ferroelectric fluoropolymer. The transistors on the other hand are based on a high-k nanocomposite gate dielectric and on pentacene as the organic semiconductor and can be operated well below 5V. It is shown, that the transistors can be fabricated on the fluororpolymer layer. Since the control of parameter spread is a very important topic in large area electronics, it was attempted to investigate the homogeneity of a significant set of devices by individual assessment of the layer composition and thickness, the pentacene morphology, the actual geometry and the electrical parameters. It turned out that starting from the measured device parameters such as layer thickness, capacitance, channel dimension, grain size and threshold voltage, the drain current can be calculated with high accuracy in a specified operation point. In addition, it is shown that the main influence on the parameter spread originates from the variations in the threshold voltage. Storage in air destroys the transistors on the long term, whereas bias stress measurements under inert conditions reveal that the interfaces are very stable.