The external quantum efficiency of white OLED can reach 76.3%

Since the first development of white OLED in the 1990s, researchers have made many attempts to achieve a balance between white spectrum and high luminous efficiency at actual brightness levels.

However, without the assistance of additional light extraction technology, the external quantum efficiency (EQE) of white OLEDs can currently only reach 20% to 40%. Of the light particles (photons) generated, approximately 20% are trapped in the glass layer of the device. The reason for this phenomenon is the total internal reflection of particles at the interface between glass and air. Later, more photons will be wave guided in the organic layer, and other photons will eventually disappear at the interface with the top metal electrode.

Researchers have devised a variety of methods to extract the absorbed photons from the OLED. It is reported that an international research team led by Dr. Simone Lenk and Prof. Sebastian Reineke of the Dresden University of Technology recently proposed a new method of releasing light particles in the famous "Nature Communications" magazine.

These physicists introduced a simple and scalable method without photolithography to generate controllable nanostructures with directional randomness and dimensional order, which greatly improved the efficiency of white OLEDs. This nanostructure is produced by reactive ion etching. Therefore, this process has the advantage that the morphology of nanostructures can be controlled by adjusting the process parameters.

In order to understand the results achieved, the scientists developed an optical model that can be used to illustrate the results of improved OLED efficiency. Subsequently, the scientists integrated these nanostructures into the white OLED, and the external quantum efficiency reached 76.3%.

For Dr. Simone Lenk, this new method opens up many new avenues: “We have been looking for a method that can be used to specifically control nanostructures. Through reactive ion etching, we have found a method that can be used on large surfaces and Economical process, and also suitable for industrial use. Its advantage is that the periodicity and height of nanostructures can be fully adjusted by process parameters, so the best light extraction structure for white OLED can be found. These quasi-periodic nanostructures The structure is not only suitable as the light extraction structure of OLED, but also has more application potential in the fields of optics, biology and mechanics."