Novel patterning techniques for manufacturing organic and nanostructured electronics

Abstract

Molecular organic semiconductors and nanometer size particles are two new classes of functional materials allowing fabrication of electronic devices on low-cost and large area substrates. Patterning these electronic materials requires the development of unconventional techniques, and the scientific understanding behind the manufacture processes. We introduce the first-generation Molecular Jet (MoJet) printing technique for vacuum deposition of evaporated thin films and apply it to the fabrication of high-resolution pixelated (800 ppi) molecular organic light emitting devices (OLEDs) based on aluminum tris(8-hydroxyquinoline) (Alq3), and the fabrication of pentacene based organic field effect transistors (OFETs) with narrow channel (15 gm) and asymmetric silver/gold contacts. Patterned printing of both organic and metal films is demonstrated, with the operating properties of MoJet-printed OLEDs and OFETs shown to be comparable with the performance of devices fabricated by conventional evaporative deposition through a metal stencil. This MoJet printing technique is reconfigurable for digital fabrication of arbitrary patterns with multiple material sets and a high print accuracy of better than 5gtm, and scalable to large area substrates.

(cont.) Analogous to the concept of "drop-on-demand" in Inkjet printing technology, MoJet printing is a "flux-on-demand" process and we show it capable of fabricating multi-layer stacked film structures, as needed for engineered organic devices. We present the concept and the applications of the second-generation MoJet printing technique. Using this technique, we demonstrate patterned molecular organic semiconducting thin films directly printed by a three-step local evaporative deposition, in conjunction with using the HP thermal InkJet printing technology. This MoJet printing technique can be applied to pattern solution-processable molecular organic thin films, providing flux-on-demand in an ambient environment. We develop an Inkjet assisted micro-contact printing technique for the patterning of colloidal semiconductor nanoparticles. Active OLEDs incorporated with a uniform thickness layer of colloidal nanoparticles are fabricated by using this Inkjet printing plus stamp transferring technique. The material usage efficiency is largely boosted. To our knowledge, these three novel patterning techniques presented in this study provide for the first time unprecedented capabilities for manufacturing organic and nanostructured electronic devices.