Quantum Dots have undeniably become the cornerstone of modern TV innovation. These high-efficiency colour converters are being used to enhance all sorts of display technologies including LCD, OLED and even micro LED. Despite their growing presence, there’s often confusion about the different types of Quantum Dot-based technologies and how they differ. Let’s break down the most popular types and highlight their differences.
Quantum dots are tiny semiconductor particles that emit light when excited. What colour of light they emit depends on the size of the quantum dot. The important thing is that there is no loss of efficiency (in a way, brightness) when colour conversion takes place via quantum dots. In comparison, when colour filters are used a significant portion of light is absorbed resulting in loss of quantum efficiency.
Also Read: 8 Different Types of OLED Display Technologies You Should Know About
Source: Samsung
Quantum dots can be classified into several types based on the material used and applications. But there are two popular types that you need to be familiar with.
Electroluminescent Quantum Dots (EL-QDs) emit light when excited by an electric current. The more popular ones are Photoluminescent Quantum Dots (PL-QDs) which emit light when excited by UV light or blue light.
QLEDs are the most popular type of Quantum Dots-based displays in consumer devices today.
Source: Nanosys
These displays use a quantum dot enhancement layer (either QDEF film or xQDEF diffuser plate) between the backlight and LCD panel.
The blue light from the backlight LEDs falls on Quantum Dots and some of it is converted to Green and Red. This results in a healthy mix of Red, Green and Blue components in the white light which is necessary to achieve a larger colour volume.
Also Check: QNED vs QLED vs OLED TVs: What’s the difference?
QLED TVs are easy to manufacture which is also why they are quite popular. LG’s QNED TVs and some of Sony’s Triluminous TVs are also based on the same technology.
QD-OLED uses a Quantum Dots layer for colour conversion, unlike WHite OLEDs which use a colour filter. It’s easy to manufacture OLED displays with red, blue and green subpixels for smartphones but not for larger display sizes like TVs and monitors.
Instead, manufacturers use a single colour emitter and then achieve colour conversion using a colour filter or quantum dots. When Quantum Dots are used, there is no loss in quantum efficiency and the display can achieve larger colour volume and higher contrast. This also enables QD-OLED TVs to be brighter than conventional white OLED TVs.
Source: Applied Materials
QD-micro LED displays are principally similar to the QD-OLED displays. The difference is that instead of organic emitters or OLEDs, these displays use inorganic emitters or micro LEDs which can last longer and can go much brighter.
Again, it’s challenging to transfer three different colour micro LEDs to a substrate and thus manufacturers see using a single blue colour emitter followed by a Quantum Dot colour conversion layer in later stages as a more pragmatic approach. QD-micro LED displays are still a few years away from consumer devices.
QDEL is one of the most promising upcoming display technologies. It is also referred to as Nano LED or QD-LED. In fact, there were times when this technology was also referred to as QNED and QLED, which were later registered by LG and Samsung for different display technologies and are now quite popular.
All the other applications that we have discussed above use Photoluminescent Quantum Dots that are excited using blue light. QD-EL or Nano LEDs on the other hand use Electroluminescent Quantum Dots which like regular LEDs can emit light when excited by current. In QDEL displays, Quantum dots do everything on their own. They don’t require an OLED or LED layer and thus offer high purity and brightness.
The technology was the prime focus at SID Display Week and TCL also showcased a 14-inch 2.8K QD-EL laptop screen prototype fabricated by ink-jet printing. This display offers a variable refresh rate (30 Hz – 120 Hz) and a wide viewing angle.
