We can define quantum dots, scientifically known as nano-crystalline semiconductors, briefly as tiny particles that glow when light hits them. A screen film consisting of these dots is the only difference that distinguishes a standard LCD from a Quantum Dot LCD. Before we go into more detail, let’s briefly review how LCD displays work.
Standard LCD TVs generally consist of three basic parts; a white backlight, color filters, and a liquid-crystal grid that groups those colors together to form pixels. Each pixel contains three subpixels of red, green and blue. These subpixels are also separated from each other by the color filters of the LED light. For example, if only the red subpixel is illuminated inside a pixel, the pixel will show only the red color. If all colors are turned on, white is displayed, if all colors are turned off, black is displayed.
LED LCDs, as their name suggests, use LED lighting to produce white light. However, the white light produced by LED lighting is also the source of one of the biggest color problems of LED LCDs.
The white LED light on LCD TVs is actually a blue LED light coated with yellow phosphor. This combination gives the LED a whitish color. In other words, the LED lighting of standard LCD TVs is not really white. This negatively affects the reflection of colors on the screen. For example, the red color produced by LED lighting will appear dimmer than the blue color displayed on the same screen. Although it was tried to reduce the intensity of other colors as a solution to this problem, the resulting image did not give the expected color.
In short, there is only one source of color problems experienced by LCD TVs; inability to use red, green and blue colors in equal intensity. At this point, Quantum Dot comes into play.
Quantum Dot
Quantum dots are tiny crystals of phosphorus that can reflect different colors in different sizes. Now that engineers can precisely control the size of quantum dots, these dots can be quite accurate at reflecting colors. Quantum dots also work quite consistently. In other words, there is no such thing as the deterioration of colors over time. The point set to reflect a particular shade of red will always show that hue.
When producing their Quantum Dot-labeled TVs, TV manufacturers layer a screen film with quantum dots to reflect certain tones of red and green, eliminating the yellow phosphor filter on the LED lighting. Thus, the blue light of LED lighting; It can combine with the screen film filled with red and green quantum dots and project a balanced white light onto the screen.
Since the quantum dot screen film does not separate the colors into subpixels, the task of projecting the image to the screen is left to the liquid-crystal grid. This time, however, the grid has a more consistent source of white light to use, allowing colors to be accurately reflected without any restrictions.
Blacks
We mentioned above that the liquid-crystal grid produces different colors by turning the color filters on and off. In pixels where all these colors are turned off, the screen must be pitch dark. However, it cannot be said that LCDs are very capable of producing true black.
The color filters that most LCDs have use some kind of cover to turn off the colors. However, these covers cannot fully keep the LED backlight behind the filter. This means that some LED light leaks into the black pixels and reduces the intensity of black colors.
Quantum dots do not have a solution in this area, because there is a certain limit to what LCD panels can do. On the other hand, the pixel lighting technology of OLED panels brings a solution to this problem. OLED panels can produce much darker blacks thanks to the pixels whose lighting can be turned on and off one by one.
