Since the first development of white OLEDs in the 1990s […]
Since the first development of white OLEDs 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 generated light particles (photons), about 20% are trapped in the glass layer of the device. The reason for this is the total internal reflection of particles at the interface between glass and air. Later, more photons will implement the waveguide in the organic layer, and other photons will eventually disappear at the interface with the top metal electrode.
Researchers have devised multiple methods to extract absorbed photons from OLEDs. It is reported that an international research team led by Dr. Simone Lenk and Professor Sebastian Reineke of the Technical University of Dresden has proposed a new method of releasing light particles in the well-known "Nature Communications" magazine.
These physicists have introduced a simple, scalable, and non-lithographic method for generating controllable nanostructures with directional randomness and dimensional order, which greatly improves the efficiency of white OLEDs. This nanostructure is created by reactive ion etching. Therefore, this process has the advantage that the morphology of the nanostructures can be controlled by adjusting the process parameters.
To understand the results achieved, scientists have developed an optical model that can be used to illustrate the results of increased OLED efficiency. Subsequently, the scientists integrated these nanostructures into a white OLED with an external quantum efficiency of 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 discovered a method that can be used on large surfaces and Economical process and also suitable for industrial use. The advantage is that the periodicity and height of the nanostructures can be fully adjusted by process parameters, so the best light extraction structure for white OLEDs can be found. These quasi-periodic nano The structure is not only suitable for light extraction structure of OLED, but also has more application potential in the fields of optics, biology and mechanics. "