Fully roll-to-roll processed organic top gate transistors using a printable etchant for bottom electrode patterning

• We produce organic transistors using only roll-to-roll techniques.
• Each step is a continuous roll process.
• Ag bottom electrodes are fabricated by a simple roll-to-roll etching process.
• The etching is completed in a few seconds, no photolithography/resist is used.
• The semiconductor is oriented during printing, depending on the gravure cup size.

We demonstrate a high throughput roll-to-roll process for preparing organic top gate transistors with metallic electrodes on a flexible substrate. The source and drain electrodes are prepared by patterning a roll-to-roll evaporated silver layer with a printable etchant. The etching step is done by a screen printing process with a novel triblock copolymer based etching ink, which enables etching in just a few seconds at low temperatures. The method allows 100 μm resolution in the roll process and can produce thin (35 nm), smooth and nonporous electrodes with high conductivity. In addition, the process is independent on the printing direction and area, providing freedom of design. The polymeric semiconductor and insulator layers are deposited with roll-to-roll gravure printing, which allows orientation – and thus performance – of the semiconducting polymer to be controlled by the cup size and printing direction. The gate is printed with rotary screen, using a solvent-free silver paste as the ink. The properties of the prepared organic transistors are typical for fully printed devices: mobility of 0.017–0.026 cm2/(V s) and ON/OFF-ratio of 102–103 were reached and the leakage current was very low (<0.1 nA).

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