According to foreign media reports, researchers at Princeton University in the United States have developed a new method to effectively improve the brightness, light efficiency and clarity of LEDs.
The research team headed by Stephen Chou, a professor of electrical engineering, developed a new system, PlaCSH, using nanotechnology. With this system, the brightness and light efficiency of the OLED are increased by 57%, and the image quality of the LED display can be improved by 400%. Researchers say their approach should work equally well for LEDs. The results of this study were published on August 19th in the online edition of Advanced Functional Materials.
Stephen said that the main problem facing LEDs today is how to reduce the light trapped inside the LED structure. Although LEDs are known for their high luminous efficacy, in reality, LEDs emit only 2%-4% of the light they produce. The light trapped in the structure not only darkens the LED, but also reduces the light efficiency, which makes the LED "short-lived", because the light trapped inside the LED will continue to heat up, greatly reducing the service life of the LED.
Stephen said: "The most important thing in the LED manufacturing process is the light extraction rate." Engineers are trying to overcome this problem by adding metal reflectors, lenses or other components to increase the LED light extraction rate. For OLEDs, these methods are indeed feasible, and the light extraction rate can be increased by 38%, but these light extraction techniques can reflect the display, reducing the contrast and making the image look blurry. So, engineers added light-absorbing materials to the display, but Stephen believes that these materials will also absorb the light emitted by the LEDs, resulting in a halving of the brightness and efficacy of the LEDs.
To this end, Princeton University researchers have used nanotechnology to develop a new system, PlaCSH, to improve the brightness and efficacy of LEDs. The picture above shows how light is trapped inside a traditional LED; and in the new system, how PlacSH directs LED light out. According to the researchers, the light extraction rate of PlaCSH LEDs is 60%, which is 57% higher than conventional LEDs.
The physics behind PlaCSH is complex, but its structure is simple. In PlaCSH, a layer of approximately 100 nm thick luminescent material is placed in a metal cavity with a metal film on one side and a 15 nm thick metal mesh on the other side. The metal mesh consists of a 20 nm wide wire. The center distance of each net is 200 nanometers. According to Stephen, the price of PlaCSH is quite cheap, because it is made of nano-embossed, just as the printing machine produces newspapers.
In addition, Princeton has filed a patent application for "OLEDs and LEDs using the PlaCSH system."