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What the LED? OLED, QLED, Mini-LED, MicroLED

Understanding OLED, QLED, Mini-LED, MicroLED — Don’t be misLED

Vincent Tabora
Jan 20, 2020 · 6 min read

What is OLED QLEDMini-LEDMicroLEDWhat the LED? Let us take a look at these technologies and what their uses are. These are all a form of LED (Light Emitting Diode), which are used in electronic displays found in televisions, computer monitors, smartphones and screens on other devices. LED are a part of the display’s panel which provides lighting for LCD screens. This is what we find on the screens of flagship smartphones, premium TV sets and high resolution monitors.

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A basic diode circuit.

LED originate from an electronic semiconductor component that emits light when current is passed through it. This works on the principles of Electroluminescence (EL), when materials emit light in the presence of electric current or strong magnetic fields. LED, which are basically diodes, allow the electricity to flow in only one direction through the semiconductor. When electrons flow through the semiconductor’s junction, photons are released which gives us light. It is from these components that OLED and other LED-based products are made for electronic displays.

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The symbol of the diode. It is an electronic component that only allows electrical current to flow in one direction through a semiconductor. The flow of electrons from one layer to fill “holes” in another layer excites the molecules and leads to the release of photons which we perceive as light.

Traditionally, LED are used for backlighting LCD (Liquid Crystal Display) displays. LCD doesn’t give off light, so they require a reflector or backlight. LED have proven to be the best choice for LCD screens (e.g. Apple Monitors).

OLED

The OLED (Organic LED) is built from an electroluminescent layer that consists of organic compounds which emit light in response to an electric current. This organic layer is between two electrodes within a substrate.

There are 2 types of OLED that I want to discuss, namely a Passive Matrix OLED (PMOLED) and Active Matrix OLED (AMOLED). In PMOLED the display is controlled sequentially using a matrix addressing scheme meaning that only m + n control signals are required to address an m × n display. AMOLED use a TFT (Thin Film Transistor) backplane that can switch individual pixels on and off. Since individual pixels cannot be manipulated using PMOLED, an AMOLED has more advantage for higher resolution and larger sized displays.

Due to their light emitting characteristics, OLED-based panels do not need backlighting. The LED are actually used for backlighting LCD displays, like in Apple’s IPS panels for their LCD Retina displays used on their MacBook and monitor products. OLED have a much better contrast ratio when it comes to displaying the blackest blacks and whitest whites. The tones show superior quality when compared to other types of displays.

Since OLED are organic, their lifespan comes into question. While red and green OLED films have longer lifetimes (46,000 to 230,000 hours), blue organics currently have much shorter lifetimes (up to around 14,000 hours). Blue light emitter remain a challenge when it comes to longevity. That could lead to color accuracy problems when the device gets older.

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The iPhone 11 Pro Max uses an OLED display (Source Apple)

QLED

Samsung marketing can be misleading with QLED (Quantum Dot LED). QLED is not the same as OLED because it is basically an LCD TV with LED backlighting. The Quantum Dots are tiny nanoparticles that dramatically improve the color and brightness of the LCD panel they are embedded in. It is a clever technique compared to conventional backlighting because it tries to simulate OLED features, by not overpowering the pixels with too much light.

In QLED the LCD matrix function like shutters to keep light from bleeding into the colors. It filters the light to recreate the colors on the display. This is a complicated technique that manufacturers like Samsung have developed for high quality displays. It can be brighter in some implementations, but does not reproduce the light and dark tones the same way as OLED. Despite that, QLED is good in color reproduction, giving a vibrant look to images and video on the display.

Why even consider QLED when you have the superiority of imaging with OLED? It is a tricky question and there are different answers. I will condense it to the following 3 points on why to consider QLED: Size, brightness and color. OLED are much harder to build for larger screen sizes and when it comes to brightness, QLED can produce more light than what individual OLED pixels can emit. More brightness is the advantage of backlit panels like QLED. Another QLED advantage is precise color quality that has been certified 100% by color volume measured to DCI-P3 standards, by the VDE Institute.

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QLED TV 8K Q900R (Source Samsung)

Mini-LED

The Mini-LED is another type of backlighting used for LCD TV. They are tinier than Quantum Dots, and almost at the pixel level. They are a form of miniature backlights that are configured in a Full Array Local Dimming (FALD) zones. They are used with QLED to provide much better control of the backlighting. This leads to better imaging quality that some say is comparable to OLED.

The features Mini-LED provide improves contrast and brightness that is similar to OLED. Like OLED, Mini-LED uses techniques that allow control at the pixel level. This allows it to achieve the level of deeper blacks that OLED displays can provide. OLED do not have backlighting since they are capable of emitting visible light on their own. Mini-LED emit lights, but still require a layer of LCD to illuminate in order to reproduce the color.

Full Array LEDs are placed in zones and can be dimmed, this is what is called Full Array Local Dimming (FALD). (Source Vizio)

MicroLED

MicroLED are similar to OLED because they emit their own light, therefore requiring no backlighting. MicroLED is actually being touted as more superior in quality to OLED displays. They can provide more brightness along with higher contrast and richer colors, combining the best features of OLED and and backlit LED.

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MicroLED uses the smallest size among the existing LED technologies. (Source TrendForce)

MicroLED are much smaller than Mini-LED. The size of the diodes are in the order of microns, so they are a millionth of a meter in size. Each MicroLED is placed in a pixel, thus they illuminate at the pixel level. Since they are tinier, they are also harder and more costly to produce, but more demand will bring economies of scale. MicroLED provide better luminance and higher resolution than OLED, so they are ideal for premium displays.

SYNOPSIS

While OLED is more commonly used for premium displays in smartphones, televisions and monitors, there are other alternatives. QLED is Samsung’s display technology that allows for larger display sizes, longer lifespan than OLED, not susceptible to screen burn-in and more brightness.

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Comparing the sizes of standard LED, Mini-LED and MicroLED.

Mini-LED optimize QLED displays by reproducing better color and contrast, similar to OLED. MicroLED are just like OLED, at the pixel level, but have much better support for high resolution images with better luminance. MicroLED may very well succeed OLED, but until another LED comes along, the market is going to be full of options for the most demanding consumers.

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