In the past two years, there’s a newish type of TV called QLED TV in the market. Samsung, the South Korean electronics giant, created the term “QLED” (abbreviation of Quantum dots Light Emitting Diode), and established a “QLED Alliance” together with its partnership: two Chinese TV manufacturers Hisense and TCL.

QLED and well-known OLED (Organic Light Emitting Diode) may have similar names, but they are different technologies. QLED technology can generate images by electrically driving illumination without liquid crystals and backlights, which can also self-emit like an OLED, but the fluorescent emissive source is not organic molecules but quantum dots.

What is Quantum Dots?
Quantum dots (QDs), known as semiconductor nanocrystals, are nanoparticles with a general particle size between 1~10 nm, and can emit fluorescence after being stimulated. Due to the different chemical composition and size of QDs, the electrons and holes are different in quantum confinement, so QDs can emit different colors of light from blue to infrared after being excited by external energy (i.e., light, electricity). “QDs are probably the best luminescent materials ever discovered by humans,” commented by Professor Peng Xiaogang (Top100 Chemists, 2000-2010, Thomson Reuters) from China’s Zhejiang University, founder of NNCrystal US Corporation (AR, USA) and NajingTech (Hangzhou, China) specializing in commercialization of QDs materials.

How QLED could be comparable to its rival OLED? Unrivalled color performance (it comes to color accuracy and volume): the simulated QDs can emit incredibly accurate R.G.B. colors with high purity and all the range of light from blue to infrared, by adjusting its size, leading to a wide color gamut. QLED’s color can match any display technology in the world. High brightness: LED displays were already good at getting extremely bright, but QLED gets even brighter. QLED is able to make all colors in the available spectrum brighter without losing saturation. In one word, QLED combines the best picture quality features of OLED with far superior brightness and colors.

Moreover, QLED display screen cost is less than half of OLED in terms of manufacturing cost. The complicated process and low production yield are always obstacles that OLED can’t overcome. In contrast, QLED is solution fabricated, such as inkjet printing, with a great advantage in mass production.

From Photoluminescence (PL) to Electroluminescence (EL)?

The QDs are mainly used for both Quantum-dot Light Converting Device (QLCD) and Quantum-dot Light-Emitting Diode (QLED). The former is already used for backlight unit in LCD (Liquid Crystal Display) screen. For example, QD vision from US and NajingTech from China offered tube-shaped QLCD (QD tube) to manufacturers like Sony, Hisense, TCL, TPV, etc.; Film-shaped QLCD (QD-Film) from 3M and NajingTech becomes the main display component of high-end TVs. The wide color gamut and high conversion efficiency (i.e., PL quantum yield for QLCD and EL external quantum efficiency for QLED) are basically sufficient reasons for large-scale commercial manufacturing. However, the final goal is commercializing QDs-infused LED, that’s real QLED, not like the QLCD combined QD-Film with LCD giving rise to a low energy-efficiency. QLED is currently still under development owing to some technical difficulties, i.e., short lifespan, low stability of blue QDs, etc. We’re still in the transitional stage between QLCD and QLED.

Samsung and TCL announced their first so-called “QLED TV” at CES 2017 and 2018, respectively, but they’re all QLCD. The true QLED sets are not yet in the market, but are anticipated to be in the coming years. Let’s wait and see the next generation display “QLED” how to shape the future of high-performance TVs.

by Jack Huang
Senior Researcher,
NajingTech, Hangzhou, China

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