The challenge in creating the next generation of organic light-emitting diode (OLED) displays is finding ways to improve color brilliance without compromising electrical efficiency. Researchers have now found a way to accomplish this by applying basic scientific principles.
OLED displays are everywhere, from high-definition smartphones to computer monitors to giant television screens. OLEDs consist of thin carbon-based semiconductor layers that emit light when electricity is applied by adjacent electrodes. OLEDs work similarly to traditional LEDs, but instead of using layers of n-type and p-type semiconductors, they use organic molecules to generate electrons.
A simple OLED consists of six layers. The top (seal) and bottom (substrate) have layers of protective glass or plastic. In between are a negative terminal (cathode) and a positive terminal (anode), and between them are two layers of organic molecules. Next to the cathode is a light-emitting layer where light is produced, and a conductive layer. next to the anode.
The organic molecules used to create these layers have inherently broad emission spectra, affecting lighting properties and limiting the range of colors (color space) and saturation available in high-end displays. increase. Color filters and optical cavities can artificially narrow the emission spectrum, which can reduce energy efficiency.
Researchers from the University of Cologne, Germany, and the University of St. Andrews, Scotland, have teamed up to tackle this problem head-on by applying a basic scientific principle of the strong coupling of light and matter.
“If photons (light) and excitons (matter) show a sufficiently large interaction with each other, they will bind strongly, producing so-called exciton polaritons,” the researchers say. “This principle can be compared to the energy transferred between two pendulums coupled, but here both light and matter are coupled with each other, continuously exchanging energy. .”
Researchers have found that embedding OLEDs between thin mirrors made of metallic materials, already widely used in the display industry, can greatly improve the coupling between light and organic materials.
To avoid the loss of electrical efficiency that usually results, the researchers added another thin film of strong light-absorbing molecules, such as those used in organic solar cells. They found that the additional layer amplifies the effect of strong light-matter coupling without significantly reducing the efficiency of the light-emitting molecules within the OLED.
“Polariton-based OLEDs are very interesting to the display industry because they have efficiency and brightness comparable to OLEDs used in commercial displays, but with significantly improved color saturation and color stability. It’s something,” said Malte Gather, the study’s lead author.
Polariton-based OLEDs (POLEDs) are already known in the scientific world, but their practical application has been hampered by poor energy efficiency and low brightness.
Having addressed these issues, the researchers hope their work will not only produce the next generation of OLED displays, but also have broader applications in lasers and quantum computing.
The study was published in a journal nature photonics.
Source: University of Cologne
