LED Differences – Variations in QLED, OLED and Mini LED
Introduction to LED, QLED and Mini LED
OLED stands for ‘Organic Light Emitting Diode’. This describes the type of panel used within an OLED TV to display all the things you see: colours, light and images. It’s this that was made by OLED different to other kinds of TV technologies, including CRT (cathode ray tube), LED (light-emitting diode), So the blacks not only lack the inky quality of their OLED equivalents but if an LCD TV’s backlight is poorly implemented and/or controlled, there can be discernible unevenness to the way the screen describes what should be uniform areas of black.
Consider the end credits of many a movie: a black screen with white text scrolling up it. It’s very common for an LCD TV to allow a halo of light to surround the words, or to let its backlight betray ‘bleed’ from the corners of the screen, turning what should be black into a cloudy grey.
A quantum dot display is a display device that uses quantum dots (QD), semiconductor nanocrystals that can produce pure monochromatic red, green, and blue light. Photo-emissive quantum dot particles are being used in a QD layer which uses the blue light from a backlight to emit pure basic colours which are improving display brightness and colour gamut by reducing light losses and colour crosstalk in RGB LCD colour filters, replacing traditional coloured photoresists in RGB LCD colour filters.
This technology is used in LED-backlit LCDs, though it applies to other display technologies which use colour filters, such as blue/UV OLED or MicroLED. LED-backlit LCDs are the main application of quantum dots, where they are used to offer an alternative to OLED displays. Electro-emissive or electroluminescent quantum dot displays are an experimental type of display based on quantum-dot light-emitting diodes. These displays are similar to active-matrix organic light-emitting diode (AMOLED) and MicroLED displays, in that light would be produced directly in each pixel by applying electric current to inorganic nano-particles.
Mini LED is at the fore of this year’s TV ranges, with the likes of TCL, Philips, LG and Samsung all pursuing the TV backlight technology. And even Apple opting to use Mini LED tech in its new iPad Pro – but what exactly is it, and why should you even care?
It is largely a TV term, but you’re likely to be seeing it in smaller devices going forward too, with the 2021 iPad Pro featuring a Mini LED backlight, and even the Nintendo Switch 2 rumoured at one point to feature Mini LED tech too. But the TV market is where the most Mini LED action is happening, and 2021 is its biggest year yet.
As the name suggests, Mini LED shrinks the LED modules that provide backlighting to LCD screens. LCD pixels can’t illuminate themselves as OLED can. So, they need a light source behind them to shine through, creating the necessary brightness and colour. Because of this extra layer of backlighting, too, the pixels in an LCD can never be turned all the way off.
In 2021, the high-end TV landscape is just as confusing to new buyers as ever. There’s a bunch of new televisions to consider, a raft of technical-sounding features 8K, HDR, Ultra HD 4K, 120Hz and HDMI 2.1 — and a stable of familiar brands competing for your dollar. Two of the biggest, Samsung and LG, use similar-sounding terms to describe their best TVs, but Samsung’s QLED and LG’s OLED are as different as day and night.
For the last few years, Samsung, the most popular TV-maker in the world, has been branding its TVs “QLED.” Its 2021 QLED lineup is massive, with Neo QLED models in 4K and 8K resolution, The Frame art TV, Serif and the Sero rotating TV all bearing the ubiquitous Q. Meanwhile, LG’s 2021 OLED TVs include six series, from the relatively affordable A1 to the wildly expensive 8K Z1 to, yes, a model that rolls up like a poster.
Classification Table for LED Differences
|OLED stands for “organic light-emitting diode.”||QLED (according to Samsung) stands for “quantum dot LED TV.”||Mini LED is largely a TV term, but you’re likely to be seeing it in smaller devices going forward too.|
|OLED is a fundamentally different technology from LCD, the major type of TV.||QLED is a variation of LED LCD, adding a quantum dot film to the LCD “sandwich.”||three commonly used device configurations: red, green and blue (RGB)-chip emissive displays, colour conversion (CC) emissive displays, and OLED-backlit LCDs. In emissive displays, mLED/μLED/OLED chips serve as subpixels.|
|OLED is “emissive,” meaning the pixels emit their own light.||QLED, like LCD, is “transmissive” in its current form and relies on an LED backlight.||The LC panel consists of M and N pixels, and each RGB subpixel, addressed independently by a thin-film transistor (TFT), regulates the luminance transmittance from the backlight.|
Both mLED, μLED and OLED chips can be used as emissive displays. While mini LEDs can also serve as a BLU for LCDs.
The full-colour images are generated differently in these three types. RGB LED chips are adopted. Each LED will emit light in both the upward and downward directions. To utilize downward light, a reflective electrode is commonly deposited at the bottom of each LED chip.
However, such a reflector also reflects the incident ambient light, which could degrade the ACR. One solution is to adopt tiny chips to reduce the aperture ratio and cover. The non-sitting area with a black matrix absorbs the incident ambient light.
This strategy works well for inorganic LEDs. However, for OLED displays, a large chip size helps to achieve a long lifetime and high luminance. Under such conditions, to suppress the ambient light reflection from bottom electrodes. A circular polarizer (CP) is commonly laminated on top of the OLED panel to block the reflected ambient light from the bottom electrodes.
each blue LED chip pumps a subpixel in the patterned CC layer (quantum dots or phosphors). An absorptive colour filter (CF) array is registered above to absorb unconverted blue light and suppress ambient excitations. This filter also enhances the ACR so that no CP is required. In some designs, a distributed Bragg reflector (DBR) is inserted to selectively recycle the unconverted blue light. And to enhance the red/green output efficiency. The blue OLED chips pump a yellow CC layer to generate a white backlight.
Brightness, layers and Enhancement Films
Additionally, a DBR could be optionally applied. In such a BLU. The OLED zones do not need to register with the subpixels so that a larger LED chip can be used. Because the CC layer scatters light. Up to two, brightness enhancement films (BEF) can be employed to collimate light onto the on-axis direction.
A dual brightness enhancement film (DBEF) can be inserted to transmit the preferred polarization. Which is parallel to the transmission axis of the first polarizer and to recycle the orthogonal polarization. The transmitted light is modulated by the LCD with an absorptive CF array.
In some designs, RGBW CFs instead of RGB CFs are employed to enhance optical efficiency. The power consumption of mLED/μLED/OLED displays is primarily determined by the driving circuitry designs. LED quantum efficiency and optical system efficiency. In this section, we describe a power consumption evaluation model and give exemplary calculations on each display technology.
The power consumption of mLED/μLED/OLED displays is primarily determined by the driving circuitry designs, LED quantum efficiency and optical system efficiency. In this section, we describe a power consumption evaluation model and give exemplary calculations on each display technology.
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