High Resolution Organic Vapor Jet Printing of Phosphorescent Organic Light Emitting Diode Arrays
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Organic light emitting diodes (OLEDs) are widely used in mobile devices due to their thin form factor, wide color gamut, and high efficiency. The introduction of OLEDs into televisions and monitors has been slowed, in part, by the difficulty of patterning organic thin films over large areas at micron-scale resolutions. A practical patterning technology must also be compatible with efficient device architectures, such as phosphorescent OLEDs (PHOLEDs). Organic vapor jet printing (OVJP) is an approach for depositing and patterning the emissive layers of OLED displays in a scalable manner. An inert carrier gas is used to mix organic vapor from multiple material sources. The vapor mixture is then distributed to a Si micronozzle array that collimates it into multiple jets to deposit well-defined thin film features onto a chilled substrate. Features smaller than 20 µm and arrays of 100 µm wide multicolor PHOLED segments have been printed by this technique. An experimentally validated deposition model predicts that full color (red-green-blue) pixel pitches of 150 µm are obtainable without cross-contamination of dopants between adjacent sub pixels. Green PHOLEDs with an external quantum efficiency of 8.0Â±0.7%, comparable to that achieved with standard techniques, were fabricated with OVJP. Since the micronozzle array is fabricated using standard Si processing techniques, this approach is readily scalable. Based on the performance of the laboratory system, a production OVJP tool has the potential to print a full color OLED emissive layer onto Gen 8 (4 m2) substrate in as little as 250s.