Fabrication and Applications of Flexible Stacked Devices via Open-Hole Integration

Abstract

We present a novel fabrication technique based on soft lithography to achieve flexible stacked inverters via hole integration. Soft lithography facilitates preparation of perforated polyurethaneacrylate (PUA) films replicated from polydimethylsiloxane (PDMS) molds. The thin PUA films (similar to 100 mu m) with open-hole structures are used as substrates of devices for stacking, and the top device can be directly connected to the bottom device via open-hole structures in stack geometry. The thin PUA substrates show high flexibility and adhesive properties, ensuring conformal contact between the top and bottom devices, and thus can be easily applied to flexible and patchable electronics. In this work, organic thin-film transistors using pentacene as an active component were fabricated on both top and bottom substrates, and the pentacene transistors show the carrier mobility of 0.166 cm(2)/V.S and on-to-off ratio of 10(5), respectively. After stacking the two devices, gold electrodes on the top and the bottom devices were electrically connected though the open hole by thermal evaporation for completing the inverter circuit. In consideration of flexible and transparent properties of PUA, this technique is highly compatible with a broad range of applications including three-dimensional device processing, organic electronics, and foldable and printable electronics.