What is QD-OLED? Why is QD-OLED better than OLED or LCD TV?

If you buy a TV, you'll find several screen technologies to choose from. The two most popular TV brands, Samsung and LG, both use QLED and OLED screens.

However, at CES 2022, Sony announced a new flagship TV model featuring Samsung's new breakthrough technology - QD-OLED screen. But what exactly is QD-OLED technology and how is it better than OLED or LCD TVs? You will learn all of that through the article below.

LCD: The first flat screen technology

LCD technology was first used in the 1960s and is still relevant today. In fact, LED, QLED and Mini-LED TVs are based on the same principle as the first LCD TVs. These displays use a liquid crystal layer to control which part of the screen receives light and how much light. However, the screen must have a light source (called a backlight) to be able to see the image clearly.

This is where the difference between LCD, LED, QLED and Mini-LED comes in. Traditional LCD screens use compact fluorescent lamps as the backlight source, while newer technologies use LED lamps. QLED adds an additional layer of quantum dots to enhance color output, while Mini LEDs use a smaller light source for more precise control.

Improvements are increasing in LCD technology

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Each development of LCD technology has solved the problems that these TVs faced. LCD screens have light edges, which means the light source comes only from the top or bottom of the screen. Furthermore, they only use compact fluorescent lamps, so they do not save energy.

LED screens, on the other hand, allow the entire screen to be lit directly from the back, meaning the LED bulb is directly behind the liquid crystal layer that provides the illumination. This technology provides a brighter display and introduces local dimming, which reduces the intensity or turns off the backlight of black areas on the screen.

QLED adds a layer of quantum dots between the backlight and subpixels. This layer converts a white backlight to red, green, or blue by changing the frequency of the light source. Doing so allows the TV's colors to appear more vibrant.

Finally, Mini-LED improves a TV's contrast by reducing the size of the backlight LED bulbs, allowing for more granular control over each dimming zone.

Light leak problem

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The way LCD/LED technology works means the screen cannot display true black. That's because there will always be a part of the TV that's lit up by the backlight. Even with local dimming, there will still be dark pixels affected by the light of the backlight.

To overcome this problem, LG developed OLED screens in which each pixel lights up individually. This means that OLED screens can produce true blacks and have the best contrast ratio among TVs.

OLED: The current gold standard of TV screens

OLED screens are considered the best when it comes to TV screens. That's because this type of display can deliver deeper blacks and higher contrast ratios when compared to other display technologies.

With an OLED display, you also get the best viewing angles. This allows users to enjoy superior picture quality whether they are sitting in front of the TV or around the edges of the TV. And finally, OLED displays are much thinner than other display technologies.

But why is that so?

How OLED screens work

Instead of requiring a layer of liquid crystals to control which pixels light up, these displays use organic light-emitting diodes, which activate when an electric current passes through it. Each pixel also has a red, green, blue (and white, in some cases) subpixel for color.

Because the brightness of each pixel is directly controlled, the display can turn off light with a high degree of precision. Therefore, there is absolutely no light in the areas where the screen appears black. This results in excellent contrast ratios unmatched by LCD/LED technology.

Furthermore, because OLED emits light directly from each pixel, these displays do not require a backlight, thus creating fewer layers. As a result, the light source is closer to the surface of the TV screen. These characteristics allow for greater viewing angles and a slimmer form factor.

Disadvantages of OLED

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Despite its top contrast and viewing angles, the OLED display has one significant drawback - it's not as bright as other alternatives. That's because OLED pixels are susceptible to burn-in, especially at the larger currents needed for higher brightness. Therefore, to prolong the life of the screen, OLED TVs are not as bright as LCD/LED options.

So if you're planning on installing a TV in a bright living room surrounded by open windows, you might want to stay away from OLED TVs.

How does QD-OLED bring great things?

Based on what's been discussed so far, current display technologies limit you to two choices: You have a TV that's bright but doesn't deliver top-notch contrast, or you have a display that offers color True black and brilliant color, but you can't see it under bright light.

This is where QD-OLED comes into play. By adding a layer of quantum dots to the blue OLED source, Samsung has reduced energy loss, thereby creating a brighter output than current OLED technologies. Let's explore this in detail below.

Quantum dots and blue OLEDs

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Before looking at how QD-OLED is better than traditional OLED technology, let's first look at what makes white light. White light includes red, green and blue colors. By combining each color, we can create white. Additionally, if we want to display green from a white light source, we will have to filter out the blue and red colors, thereby reducing the brightness of the source.

Now consider a white OLED display with 4 color subpixels - red, green, blue and white. The red, green, and blue subpixels filter out about 66% of the source's brightness. So if you want to display white on this OLED screen, you only see about 50% of the original brightness of the OLED underneath.

Samsung's QD-OLED gets around this by using blue as the color of the base OLED. Samsung then used a quantum dot (QD) layer for each subpixel to distribute red and green colors. Since blue has the shortest wavelength among the primary colors, the QD layer increases it by absorbing some energy to change the blue to red or green.

This is more efficient because the energy (hence brightness) lost in the transition from blue to red or green is estimated to be only about 10%. Blue, on the other hand, doesn't need any conversion to get the total brightness of the OLED.

So if you look at white with a QD-OLED pixel, you'll see about 90% of the original brightness of the blue OLED underneath. This not only makes the display brighter but also makes it more energy efficient.

QD-OLED for better colors and better viewing experience

This development further enhances the already excellent color quality of OLED displays. What's more, it can now deliver brightness competitive with LCD/LED displays while retaining the ability to deliver deep, true blacks.

With improved brightness and enhanced colors, this new OLED technology ensures users can enjoy HDR content superbly. That way, we can watch movies and videos the way the creators intended their audiences to enjoy them.

Marvin Fry

Update 14 October 2023