Fabrication of Organic Thin-Film Transistors on ThreeDimensional Substrates Using Free-Standing Polymeric Masks Based on Soft Lithography

Here, a novel fabrication technique for integrated organic devices on substrates with complex structure is presented. For this work, free-standing polymeric masks with stencil-patterns are fabricated using an ultra-violet (UV) curable polyurethaneacrylate (PUA) mixture, and used as shadow masks for thermal evaporation. High flexibility and adhesive properties of the free-standing PUA masks ensure conformal contact with various materials such as glass, silicon (Si), and polymer, and thus can also be utilized as patterning masks for solution-based deposition methods, such as spin-coating and drop-casting. Based on this technique, a number of integrated organic transistors are fabricated simultaneously on a cylindrical glass bottle with high curvature, as well as on a flat silicon wafer. It is anticipated that these results will be applied to the development of various integrated organic devices on complex-structured substrates, which can lead to further applications.