Tag Archives: LCD

Samsung may be on the brink of self-emissive QLEDs

Researchers at Samsung Electronics recently described a new method that extends the lifetime and efficiency of quantum dot light-emitting diodes (QLEDs). Although researchers are still not sure if they will ever be able to commercialize self-emissive QLED displays, this technology may become a defining component of flagship TVs and displays in the future.

Samsung’s commercially available QLED TV sets don’t actually use quantum dots as the light source. But it happen as early as 2025, South Korean researchers say. Credit: Amazon.

Quantum dots are artificial nanoscale crystals that can transport electrons and have varied properties, depending on their shape and material. Researchers first noticed in the early 1980s that if they made semiconductor particles small enough, quantum effects would come into play — enter the world of quantum dots.

What we now know about quantum dots is that their optical properties can be finely tuned depending on their size. For instance, these nanoparticles can be made to emit or absorb specific wavelengths of light — which is essentially color — by controlling their size. A 3-nanometer quantum dot can convert a spectrum of light into green while a 6-nanometer quantum dot gives off the color red.

Due to their appealing physical properties, quantum dots can be employed in a wide range of applications in such areas as electronics, photonics, information storage, solar energy, medicine, sensing, or medicine — to name just a few.

Most people have heard of quantum dots because of TV screens. Samsung Electronics and LG launched the first QLED TVs in 2015.

However, these TV sets do not use QEDs as a light source. Instead, a liquid crystal display (LCD) acts as the backlight, which is absorbed by a film of quantum dots that emits luminance. But in the future, self-luminating QLEDs might become a reality.

In a new study published in the journal Nature, researchers at Samsung, led by Dr. Eunjoo Jang and Dr. Yu-Ho Won, improved the structure of a quantum dot made out of indium phosphide.

The study describes how the novel structure prevents oxidation of the core and prevents energy from escaping by wrapping the quantum dot into a thick shell.

Results show that the quantum dot diodes have a lifetime of a million hours. Their efficiency also improved by 21.4% compared to the previous record holder. Another important achievement was the usage of indium phosphide, which is non-toxic and environmentally friendly. Most QLED research has employed cadmium, which has the highest performance as a light source due to its extraordinary malleability and integrity. The problem is that cadmium is toxic.

Quantum dots are both photoluminescent and electroluminescent, both properties that will be at the core of the next-generation of displays. Compared to organic luminescent materials used in organic light-emitting diodes (OLDEs), quantum dot-based diodes have purer colors, longer lifetime, lower manufacturing cost, and lower power consumption. And since quantum dots can be deposited on any structure — you can literally spray or paint them on surfaces — QLEDs can be flexible or printed.

Samsung seems very serious about this technology. In October, it vowed to invest $11 billion by 2025 to produce genuine, self-luminating quantum dot displays. The South Korean tech giant has so far over 170 patents on element structure in QLEDs.

Subpixels no antialiasing.

Power to the subpixel: new tech could triple the resolution of LCD screens

University of Central Florida researchers might triple the resolution that LCD screens can pump out by three-fold, virtually overnight. The breakthrough was made possible by a novel surface which allows individual subpixels to display any of the three primary colors.

Television.

Image credits Alexander Antropov.

TVs and every other type of screen have gone a long way since their humble beginnings. But if there’s one thing consumers will always fawn over it’s got to be a bigger, better, crisper display. The first two usually are just a question of how much money you’re looking to spend, while the latter — well, it’s had a hard cap up to now.

One image to rule them all

Think of screens as a reverse compound eye. They build the complete image by stacking lots of tiny images — pixels — together, and by altering each pixel’s color, you alter the final image. In turn, each pixel is built by stacking three tinier images — subpixels — on top of one another. But subpixels are locked to a single color, either red, green, or blue, the three primary colors in television.

A white backlight shines through the subpixels and they’re either turned on or off by a shutter to create the pixel’s final color. For example, if the pixel has to be blue, the LCD shutter will block out the green and red subpixels. If it has to be purple, it will only cover the green subpixel, and so on. Finally, the intensity of the backlight determines the overall brightness of the screen and how light or dark the final color will be.

Subpixels no antialiasing.

Simulation of how an LCD renders a Wikipedia’s infamous ‘W’ in black on a white background. No antialiasing.
Image credits Michael Geary.

So far, so good. The LCD has proven itself on our smartphones, computer screens, TVs and more. But because of its dependency on subpixels there’s a limit to how much resolution it can carry over a given surface. So the way to get a better resolution up to now was to just make the screen bigger, making it more expensive and less portable.

To address the limitation, a team from the University of Central Florida’s NanoScience Technology Center went the other way around and made the subpixel smaller — by making them be the pixels. The researchers showed that by using an embossed nanostructure surface and a reflective aluminum surface, they can create subpixels which can change color as needed. So rather than having one green, one red, and one blue subpixel make up a pixel, each subpixel of the “full-colour plasmonic display” can produce the entire range of color that the screen is capable of displaying.

Less is more

Whoa, right? In theory, since each 1/3 of a pixel can now function as a pixel in its own right, the team’s tech can support three times the resolution of a traditional LCD of similar dimensions. Furthermore, each of these tiny pixels will be on unless they have to render black, meaning the screens will be far brighter than traditional LCDs.

Traditional LCD screen displaying a diagonal white line on a black background. Lines 1 and 3 — no antialiasing. Lines 2 and 4 — with antialiasing to make the line smoother, less blocky.
Image credits Devon Fyson / Wikimedia.

One downside, however, is that the screen is a tad limited in regards to frame rate. The display’s cycling times are “are somewhat invariant to voltage and in the 70 ms range, which equates to 14 Hz.” While this isn’t slow, it’s just not on even footing with the refresh rates traditional LCDs deliver, and nowhere near what high-end LCDs can churn out. So while it will work well on your phone and for other applications where frame-rate isn’t really an issue, if you want to play a fast-paced computer game it just won’t cut it.

But the technology is still in its infancy and as the team notes, it’s already “orders of magnitude faster than other colour-changing technologies”. Hopefully, these teething problems will probably be addressed in time. If so, it could mean a huge step up in image resolution — and as such quality and fidelity. First, however, the team plans to show that the screens are compatible with current hardware by scaling up their prototype.

“It allows you to leverage all the pre-existing decades of LCD technology. We don’t have to change all of the engineering that went into making that,” said Daniel Franklin, co-author of the paper.

The paper “Actively addressed single pixel full-colour plasmonic display” has been published in the journal Nature.