Appearance of a 64-pixel organic EL display created using this method and an image of the characters "HELLO" scrolling on the display
``3D-printed flexible organic light-emitting diode displays'' developed by a research team consisting of the University of Minnesota in the US, the Korea Institute of Industrial Technology (KITECH) in South Korea, and Pusan National University in South Korea is a customized tabletop 3D printer. It is a system that can be used to completely create an organic EL display (OLED). Since the entire display is covered with silicon, it is highly flexible and continues to emit light even when it is bent. [Image] View from the side with the display bent This time, we will prototype an 8 x 8 64-pixel organic EL display with a side of about 4 cm. The functional parts of the OLED display consist of six layers 3D-printed on a polyethylene terephthalate (PET) flexible film, and from bottom to top, the structure is as follows. - Bottom wiring printed with silver nanoparticle (AgNP) ink.・A conductive polymer PEDOT:PSS (polyethylenedioxythiophene and polystyrene sulfonic acid dispersion) arranged in a thin film. • Thin-film arrays of MDMO-PPV, a electroluminescent polymer. An active layer that emits light by recombination of electrons and holes.・A silicon-based insulating layer that exposes only the active region of the organic EL to the cathode. • An array of eutectic gallium-indium (EGaIn) droplets, later reconstituted to form the upper cathode structure. • Create terminal contact pads in an array of top interconnects that interact closely with the EGaIn array. In order to form these six layers of different materials, we made improvements to integrate two different ink supply methods (extrusion printing and spray printing) on a common 3D printer. Only the deposition of the MDMO-PPV thin film used a spray printing method in which the ink of the active material is atomized. Compared to extrusion-printed active layers, spray-printing provides better layer uniformity and controllable thickness. The performance of an organic EL display is affected by the uniformity and thickness of the active layer, so it can be said that it is an essential approach to improving the reliability and performance of the device. The remaining five layers are deposited by a pneumatically operated extrusion printing process. This time, in order to create a bendable organic EL display with high flexibility, the base material and six layers were sealed with PDMS (polydimethylsiloxane), a type of silicon. An 8×8 organic EL display, with anodes and cathodes electrically interconnected along the same column and row respectively, processes in a passive manner, with data and scan signals input to two electrode sets. As a result, it was confirmed that all the pixels of the 3D-printed organic EL display worked normally, and information such as characters and images could be scrolled. In the bending endurance test, it showed a relatively stable luminescence result over 2000 bending cycles. Source and Image Credits: Journal Article, Ruitao Su, Sung Hyun Park, Xia Ouyang, Song Ih Ahn, and Michael C. McAlpine “3D-printed flexible organic light-emitting diode displays” SCIENCE ADVANCES, 7 Jan 2022, Vol 8, Issue 1. DOI: 10.1126/sciadv.abl8798 * Written by Hiroki Yamashita, who presides over the web media "Seamless" that introduces the latest research in technology. Mr. Yamashita picks up highly novel scientific papers and explains them.
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