Ambient Environmental Patterning of Organic Thin Films by a Second-Generation Molecular Jet (MoJet) Printer

Organic light emitting device (OLED) technology for use in flat panel display (FPD) applications would benefit greatly from the development of a reliable, repeatable, additive patterning tech¬nique of forming organic electroluminescent (EL) thin films. We previously demonstrated that the first-generation molecular jet (MoJet-I) printing technique is superior to the two industrial mainstream methods to pattern the EL layers, namely shadow- masking patterning for molecular organics and InkJet printing for polymeric materials. We present here the concept and application of the second generation (MoJet-II) printing technique. Using an improved silicon MEMS printhead, we demonstrate the feasibility of ambient environmental patterning of molecu¬lar organic EL thin films directly by local evaporative deposition. Three stages are involved in the printing process. In the first stage, thermal InkJet printing technology is used to dispense ink drops into a micro-machined silicon membrane consisting of an array of 8 by 8 micro-pores and an integrated heater. Once the pores are filled, in the second stage, a small current is passed through the heater to completely drive off solvent from the micro-pores. In the final stage, a pulsed current of larger magnitude is applied to heat up the pores to a temperature sufficient to discharge the dry ink materials out of the pores and form molecular flux. The flux is then condensed onto a nearby substrate, forming designated thin-film ELpatterns.

MoJet printing combines the advantages of the film purity of thermally evaporated films with the flexibility of direct patterning to enable "flux on demand" deposition of molecular organic thin film with scalability over arbitrary form/size substrates. ambient environmental patterning can enable high-quality, low-can enable high-cost, on-demand digital fabrication of organic devices.