German researchers are developing a breakthrough method that would make OLED screens cheaper and improve their luminosity.
The team of the Fraunhofer Research Institution for Organics, Materials and Electronic Devices managed to produce mini-OLED screens without using colour filters, substituting their function by an innovative coating technology.
The currently used colour filters are suppressing self-radiance of the OLED displays, so that only about 20 per cent of the emitted light can be used.
By spraying the red, green and blue sub pixels directly onto the OLED unit, the team managed to avoid using the filter entirely. “The sub pixels in the tiny display are typically about 8 square micrometres in size. However, conventional technology only allowed for the processing of units greater than 50 square micrometres,” explained the research leader Rigo Herold.
To address the problem, the team employed a special technology developed by their partner VON ARDENNE – world's lead manufacturer of advanced coating equipment.
The technology facilitates targeted vaporization of organic layers locally, under heat, thus enabling processing of surfaces smaller than 10 square micrometres. “In order to use the technology for OLED micro displays, we redesigned the entire manufacturing process. It is therefore possible to load the red, green and blue colour pixels directly. The use of the colour filter is no longer necessary and it is possible to use 100 per cent of the light emitted,” Herold said.
As it has been the expensive colour filters what has been driving the costs of OLED production unreasonably high, the new technology promises to make the whole process much more affordable.
OLEDs, standing for Organic Light Emitting Diode, unlike ordinary crystal display screens, don’t require background lighting and make it possible to manufacture flexible, bendable displays as thin as a sheet of paper.
However, the technology is still in its infancy with short lifespans and high acquisition costs being the major obstacle.
Right now, OLED is being used mostly for screens of sizes of just a few square centimetres such as the ViewFinder on digital cameras or – even smaller – on mobile phone beamers