Optimized circuit design for flexible 8-bit RFID transponders with active layer of ink-jet printed small molecule semiconductors

We ink-jet print a blend of 6,13-bis(triisopropyl-silylethynyl)pentacene and polystyrene as the active layer for flexible circuits. The discrete ink-jet printed transistors exhibit a saturation mobility of 0.5 cm² V ^-1 s^-1. The relative spread in transistor characteristics can be very large. This spread is due to the morphology of the TIPS-PEN crystals, and is difficult to control using inkjet printing. Here we apply a novel circuitry design to minimize the probability of differences between the transistors. We include up to four transistors under the same ink-jet printed deposit. With the new design, we demonstrate unipolar circuitry building blocks such as inverters, NANDs and 19-stage ring-oscillators. Additionally, we integrate almost 300 TFTs, on a surface area of 34 mm² of plastic foil, for 8-bit RFID transponder circuits.