Stanford University’s collaboration with Samsung paid off – achieving an OLED display with a density of 10,000 ppi

Stanford University’s collaboration with Samsung paid off – achieving an OLED display with a density of 10,000 ppi

Stanford University’s collaboration with Samsung paid off – achieving an OLED display with a density of 10,000 ppi Pixel density is one of the important factors in display quality. is considered. Currently, the 4K display in the smartphone Xperia 1 II has the densest display among 2020 smartphones with a density of 643ppi. But according to the recent news from Stanford University Published, with a special method, the density of the screen can be increased to more than 15 times what was said. Samsung company researchers, in collaboration with researchers from Stanford University, have succeeded in designing an OLED display with a density of about 10,000 ppi. To better understand the issue, it is good to know that a 6-inch display with a resolution of 32K (equivalent to 17,280 x 30,720 pixels) will have a density of approximately 6,000 ppi!

Achieving a pixel density of 10,000 ppi is the result of the research of a material science scientist at Stanford University It is called “Mark Brongersma” (Mark Brongersma), which was obtained as a result of his collaboration with “Samsung Advanced Institute of Technology” or SAIT. Brangerzma initially entered this research with the aim of creating ultra-thin solar panels.

Mark Brangerzma, a professor of materials engineering at Stanford University, described his research by publishing an article in the prestigious journal Science on October 22 (November 1). He says: “We have taken advantage of the fact that at the nanoscale, light can float around objects like water. The field of nanoscale photonics has always been full of new surprises, and now we have begun to influence real technologies. Our designs worked very well for solar cells, and now we have the opportunity to influence the next generation of displays.”

OLD’s “paraphotonic” or metaphotonic displays also set a new record for pixel density. Compared to the current versions, they are brighter and have higher color accuracy. In addition, the production of these displays will be easier and less expensive.

Hidden Gems

At the heart of an OLED display is an organic light emitting material. These materials are placed between highly polished and semi-transparent electrodes from above and below, which allow the injection of current into the device. As electricity flows into the OLED, the emitters emit red, green, or blue light. Each pixel in an OLED display is made up of smaller sub-pixels that produce these primary colors. When the resolution is high enough, these pixels are visible to the human eye as one color. OLEDs are an attractive technology because they are thin, light and flexible, and produce brighter and more colorful images compared to other types of displays.

In total, we have two types of OLED displays, and this research aims to provide an alternative for these two types. The first type – called red-green-blue (RGB) OLED – has individual subpixels, each of which contains only one color of emitter. The manufacturing process of these OLEDs is done by spraying each layer of material through a fine metal mesh to control the composition of each pixel. Of course, it should be noted that this type of OLEDs can only be produced on a small scale, such as the display used in smartphones.

But the second type of OLEDs – which is called white OLED – is used in larger devices such as televisions. . In this type of OLEDs, each subpixel contains a set of all 3 emitters and a filter is used to determine the color of the final subpixel. In this way, it will be easier to make these types of OLEDs. Because filters reduce light output, white OLED displays are more energy-efficient.

When Won-Jae Joo, one of the scientists of SAIT (Advanced Technology Institute Samsung), visiting Stanford University between 2016 and 2018, had ideas about OLED displays in mind. At that time, he listened to a lecture by one of the graduates of Stanford University named Majid Esfandiarpour about the ultra-thin technology of solar cells. Esfandiarpour was developing these cells in the Brangerzma laboratory and realized that these cells have other uses in addition to generating renewable energy from the sun.

After Esfandiarpour finished his lecture, Joe approached him with an idea he had in mind, and this led to the formation of a collaboration between researchers from Stanford, SAIT, and Hanyang University in South Korea. According to Esfandyarpour, it is very interesting that a problem that was previously thought of in a different context can have such a significant impact on OLED displays. Joe, who is one of the lead authors of a paper published in the journal Science, said: “The research topics of Brangerzema were all very deep and fundamental academically, and to me as an engineer and researcher at Samsung Electronics, they were like hidden gems.” /p>

A basic foundation

The main innovation behind solar panels and the new OLED display is a base layer of polished metal with very small wrinkles on the nanoscale (smaller than the microscopic scale). . This layer is called “optical metasurface”. This metasurface can provide the possibility of intensifying different colors in pixels by manipulating the reflective properties of light. These resonances play an important role in facilitating efficient light extraction from OLEDs.

According to Brangerzma, this is just like the process in which musical instruments use acoustic resonances to produce beautiful melodies that are easily audible.

For example, red emitters have longer wavelengths compared to blue emitters, and this in RGB OLEDs means subpixels with different heights. Therefore, in order for the display to have a flat surface, the materials accumulated on top of the emitters must be placed on top of each other in unequal thicknesses. In contrast, in this new OLED, the folds in the base layer make each pixel have the same height, which simplifies the process of producing displays (both on a large scale and on a small scale).

It should be noted that researchers succeeded in producing miniature pixels (proof-of-concept) in laboratory tests. Compared to white OLEDs (with color filters) – which are currently used in OLED TVs – these new pixels have higher color purity and their luminance efficiency is doubled. Brightness efficiency means the degree of brightness of the display in relation to its consumption.

As mentioned before, about 10,000 pixels are placed in each inch of the screen that is made of these pixels. The density of 10,000 pixels per inch can produce stunning images with real-world details. These features make such a display a suitable option for use in virtual reality and augmented reality headsets that are only a few centimeters away from the face. Needless to say, this display is currently made in the laboratory and the next step is its commercial production, which is followed by Samsung.

You might think that it is impossible to reach a density higher than 10,000 ppi, but the simulations of this research team show that theoretically, the maximum density that can be imagined for a display is 20,000 pixels per inch. Of course, in order to achieve such a density, a serious challenge is on the way of the researchers: creating a balance in the brightness, when the pixel dimensions are reduced to less than 1 micron.

Not to mention, some other research groups have also developed screens whose density is said to vary between 10,000 and 30,000 pixels. Among these displays – which are designed thanks to micro-LED technology – we can mention Jade Bird Display in China and VueReal in Canada. Of course, Brangarzma claims that their display has a higher color purity.

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