What is the difference between an AMOLED screen and an LCD screen?

In the current mobile phone industry, if divided according to the screen material, the mainstream screens are generally only LCD and AMOLED. Maybe you can tell some basic features of these two screens, such as AMOLED screens have a wide color gamut, and LCD screens are wider. Mature, but do you know what is the difference between the two screens from a technical point of view?

AMOLED

AMOLED is actually the abbreviation of Active Matrix Organic Light Emitting Diode, and the core is still in Light Emitting Diode, that is, LED. Although LEDs are relatively common in daily life, in the screen, each LED is very small in size and is divided into three sub-pixel groups of red, green, and blue, and then forms different colors, and the arrangement of sub-pixels The method will also affect the overall display effect.

The O in AMOLED stands for Organic, that is, “organic”. Simply put, a series of organic thin film materials are used between the positive and negative electrodes to achieve the purpose of emitting light.

Finally, AM stands for Active Matrix, which is relative to Passive Matrix and refers to the driving method of each OLED pixel. In Passive Matrix, the control of each pixel is realized through a complex electrode network, so as to realize the charge and discharge of a certain pixel. Generally speaking, the control method of Passive Matrix is ​​relatively slow and the control accuracy is slightly lower. Unlike Passive Matrix, Active Matrix is ​​equipped with a TFT and a capacitor layer on each LED, so that when a certain row and column are energized to activate the intersecting pixel, the capacitor layer in the pixel can be refreshed between two refreshes. Stay charged, allowing for faster and more precise pixel lighting control.

The main advantage of OLED screens is the high degree of controllability of the pixels, each of which can be switched on and off independently, resulting in purer blacks and higher contrast. In addition, power consumption can be reduced by turning off unneeded pixels when displaying images. At the same time, since there are fewer layers inside the screen module, the light transmittance is also better, which is conducive to achieving higher brightness and wider viewing angles.

Compared with LCD, OLED screens can be made very thin, which is very suitable for mobile devices such as mobile phones. In addition, due to the lack of a hard backlight layer and the maturity of flexible plastic substrates, OLEDs also have great advantages on flexible screens, creating more possibilities for future mobile devices and even wearable devices.

LCD

After talking about AMOLED, let’s talk about LCD. The full name of the LCD is Liquid Crystal Display, and the way it emits light is very different from that of AMOLED screens. Unlike AMOLED screen pixels that can emit light independently, all pixels of LCD screen need to rely on a unified backlight layer for light emission. Of course, for the large-size LCD screens used on some TVs, itheymay also be equipped with multiple light sources to reduce power consumption.

Strictly speaking, there is no certain wavelength corresponding to white light in the world, and white light is just a mixed light of multiple colors of light. For this reason, LCD can only produce white backlight through backlight phosphor, and the combination of blue backlight and the yellow phosphor is most commonly used.

The white light generated by the backlight layer will be the first polarizing layer, which converts fully polarized light into linearly polarized light with a uniform vibration direction, and then passes through the liquid crystal molecule layer. According to different voltages, the liquid crystal molecules will have different twist angles, thus Polarize the white light, reversing the vibration direction, and then pass through the red, green and blue filters to produce different colors, and finally pass through the second polarizing layer (perpendicular to the first layer) to control the light intensity, and finally different colors are realized by combining the intensity of three different colors of red, green and blue light.

Similar to OLED, LCD drive methods can also be divided into Active Matrix and Passive Matrix. Currently, most LCD screens on mobile phones use Active Matrix.

AMOLED vs LCD

The biggest difference between AMOLED and LCD screens is that AMOLED generally has a wider color gamut, can display more colors, and the displayed picture will be more flattering. In addition, when displaying blue and green, AMOLED screens have higher saturation, so early AMOLED screens were often criticized for inaccurate colors and too bright colors. Compared to AMOLED screens, LCD screens usually overcompensate reds a bit while suppressing greens a bit, and while LCD screens don’t have as wide a color gamut as AMOLED screens, they’re actually closer to the standard RGB gamut used for video and photo editing.