OLED screens on the way to being printed in a single layer
German scientists have developed a prototype of an organic LED with only an organic-semiconductor layer. The new method can push development towards printable OLED screens
Are you looking for a new OLED screen, either for your TV in the living room or your smartphone, then you have several different brands and brands to choose from. But they are virtually all produced in either South Korea or China by the electronics giants LG and Samsung.
Today, for example, only South Korean LG Display can mass-produce OLED TV panels from its two factories, one in South Korea and a new one in China, which has just opened and has cost dizzying $ 25 billion.
This is due, among other things, to the fact that the manufacturing process behind OLED is enormously complex, where up to seven different layers of organic semiconductors must be placed on top of each other, which in turn must be connected in a giant network of millions of pixels on a flat screen.
But now German polymer scientists from the Max-Planck Institutions für Polymerforschung (MPI-P) in Mainz have presented a new, active principle that can reduce the number of organic semiconductor layers from seven to just one layer that gets current supplied via two electrodes.
The first prototype can already compete with existing products in terms of power and brightness. So says Dr. Gert-Jan Wetzelaer, who, together with his colleagues in German Mainz, has published his findings in a scientific article in Nature Photonics.
Can be printed in one piece
OLED stands for organic light-emitting diodes, ie organic LEDs, and consists of organic components, primarily of carbon, as opposed to conventional LED diodes that also contain gallium. This means that OLED components will often have a lower brightness and lifetime, limiting the spread of OLED in both large flat screens and mobile phones, because components are significantly more difficult to handle.
The German scientists have succeeded in reducing the complexity with a light layer based on the physical principle of Thermally Activated Delayed Fluorescence (TADF). The principle has been known for decades and has been investigated for OLED over the past ten years because it can be used to effectively convert electrical energy into light. In this way, the German polymer scientists believe they can do without the costly rare earths currently used to manufacture existing OLED screens to compensate for the lower brightness and lifetime
2.000 hours of life
In the Nature Photonics article, researchers describe how in an experiment they have succeeded in emitting light with a strength of 10.000 candela / m2 (the SI unit for brightness, ed.), which is 100 times stronger than existing OLED screens and is considered as a world record, partly because they could simultaneously measure an external efficiency of 19%, which is the percentage of electric energy converted to light.
Subsequently, the researchers have tested the lifetime of the OLED prototype, which they have been able to use for 2.000 hours, with a brightness of 10 times the existing screens. Over 2.000 hours, the brightness decreased by 50 percent.
"We hope that we can further improve the concept and achieve even longer lifetimes. This will enable the concept to be used for industrial purposes", says Jan Wetzelaer.
By producing organic LEDs with a TADF-based method, the German researchers expect that they can print OLED components directly in one piece from an inkjet printer because the diode becomes one-dimensional. Thus, it may be possible to produce small OLED screens placed in, for example, clothes or on other flexible surfaces at a reasonable price.
https://ing.dk/artikel/oled-skaerme-paa-vej-at-blive-printet-enkelt-lag-227270
