Tomas Backlund

Development of TFT device stack for integration of organic semiconductors into flexible displays

To enable the integration of organic transistors into flexible displays we have developed passive materials for a robust, layer-to-layer compatible device stack to be manufactured using a variety of industrially applicable coating and printing processes. The solution processable materials for the OSC protection and the passivation material are designed for good interlayer adhesion and OTFT stability. The 365 nm UV-curable protection layers for the OSC are compatible with fabrication processes commonly used in the display industry, e.g., sputtering of metals. Fabrication of ink-jet printed devices is demonstrated with usage of a passive material suitable for further pixel integration. The bias stress and ambient stability was shown for the integrated stacks of transistors with the carrier mobility greater than that of amorphous silicon. We further demonstrate the development of formulations, suitable for high throughput roll-to-roll processing of soluble small molecule semiconductors allowing a high degree of structural order in the final solid film. Transistor mobility <2 cm2/V·s is achieved with a range of viscosity values compatible with flexographic printing. Fine pattern of OSC is demonstrated with flexographic printing by adjusting the viscosity of the formulation. Uniform layers are achieved with coating and printing techniques and uniformity values are sufficient for display application.