Better, cheaper OLED micro displays do away with color filter
Production of organic LEDs (OLEDs) today is rather expensive. For this reason, OLED screens so far have not gained mass acceptance. The research project of a team around Rigo Herold from Fraunhofer COMEDD (Dresden, Germany) could bring OLED microdisplays production closer to the desired goal.
The research team now announces a major breakthrough: Together with Von Ardenne Anlagentechnik GmbH, the researchers developed a manufacturing process that does away with color filters. In conventional processes, such filters are required because the red, green and blue subpixels could not be applied directly to the electrodes. Typically, the subpixels in such OLED micro displays have a size of about eight square micron. Conventional manufacturing technology however was unable to process areas smaller than about 50 square microns.
In order to resolve this problem, the research team utilized the Flash Mask Transfer Lithography (FMTL) coating technology developed by Von Ardenne Anlagentechnik. This technology makes it possible to selectively vaporize organic layers, enabling users to manipulate areas smaller than 10 square microns. This in turn makes it possible to deposit the color subpixels directly. For this reason, no color filter is required anymore. This reduces the manufacturing costs for the OLED manufacturing process since the filters itself are rather expensive and their assembly requires a high degree of exactness which significantly adds to the overall cost.
And there is another benefit: The technology utilizes 100 percent of the light generated. The color filter reduces the overall brightness of such an OLED by as much as 80 percent. This high reduction rate is caused by two factors: One is that it suppresses two of the three color ranges of an OLED subpixel, respectively. The second reason is that as a layer on top of the OLED reduces the amount of light passing through it.
By saving overall energy consumption, the new technology also could improve the operating time of battery-powered devices such as smartphones or digital cameras, the researcher said.
The technology will be discussed in detail during a presentation at the SID Display Week which will take place in Vancouver, Canada, from May 21 trough 23.
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