Technical Interpretation: Why do mobile device giants have a soft spot for AMOLED panels?

Recently, Apple Watch, Samsung Galaxy Gear, S6 and other smart watches and smart phones have adopted AMOLED panels, and even domestic first-line mobile phone manufacturers have begun to introduce AMOLEDs in order to increase the added value of products, regardless of these wearables. Which AMOLED panel is used by equipment and smartphone vendors, but from the trend of Apple and Samsung, the AMOLED panel market seems to be turning over!

Apple's Apple Watch uses LG AMOLED panels. (Source: Apple, 2015/05)

Apple's Apple Watch uses LG AMOLED panels.

Why is AMOLED the "new darling" of recent wearables and even smartphones? Will the future be heavily adopted on mobile devices? Let's first take a look at some of the technical information of AMOLED.

Introduction of AMOLED

Before talking about AMOLED, we must first talk about OLED technology. After all, AMOLED is a kind of OLED technology. OLED is the meaning of organic light-emitting diodes, which can achieve self-illumination without using a backlight. At the same time, the viewing angle is wide, the image quality is uniform, the reaction speed is fast, the color is easy to be colorized, and the simple driving circuit can achieve the illumination and the process is simple.

The principle of OLED illumination is to deposit an organic film between a transparent anode and a metal cathode, inject electrons and holes, and use it to recombine between organic films to convert energy into visible light. Can be used with different organic materials to emit different colors of light to achieve the needs of full color displays. OLED technology was developed in the 1980s, and commercial applications began in the late 1990s.

OLED can be divided into two types: PMOLED (Passive Matrix OLED) and AMOLED (AcTIve Matrix OLED). The OLED passive mode is simpler to construct. In the case of large-size application products, there will be problems of high power consumption and reduced lifetime. . Therefore, the current active drive mode develops rapidly, because the active current rectification is better than the passive mode, and it is not easy to generate leakage phenomenon, which meets the requirements of large-size, large-screen OLED displays, so AMOLED can be applied not only to mobile phones, but also to 55-inch. AMOLED TV has also appeared.

AMOLED display schematic

AMOLED display schematic

In AMOLED, OLED describes the specific type of thin film display technology - organic electroluminescent display, AM (active matrix) refers to the pixel addressing technology behind. The AMOLED displays light that is previously stored or integrated into the TFT after being electrically excited by the OLED matrix molecules, and acts as a set of switches to control the flow of current to each pixel. TFT backplane technology is the key to making AMOLED displays.

The characteristics of AMOLED (from the perspective of intuitive user experience)

1. The screen has self-illuminating characteristics, which is quite different from the passive display that requires the back light to be displayed on the LCD panel. This type of screen has a larger viewing angle. Many people think that too much viewing angle is not necessary, this view is not correct. If you often play games controlled by gravity sensing, such as wild car racing, you can deeply appreciate his importance.

2, AMOLED screen has the characteristics of low power consumption, it can bring longer battery life so that users can enjoy the rich functions of embedded devices around us at any time.

3, AMOLED screen color is more vivid, brightness performance is also better. It can still maintain good visual effects under strong outdoor light.

4, AMOLED screen has a higher contrast ratio, compared with the traditional TFT screen, AMOLED shows black, is thick and pure black, and TFT is more like dark gray in comparison; AMOLED white is also pure white, thus Achieve a more transparent display.

5, AMOLED screen has a faster response speed. Can bring users a smoother touch experience.

6, AMOLED screen has a more "light", more "thin" body advantage, can make the design of embedded devices such as mobile phones or tablets more light and thin.

Well-known developer Craig Hawken Berry said that the AMOLED material screen that Apple first adopted in Apple Watch has self-illuminating characteristics, thus greatly reducing the need for internal space of the device. However, the screen of this material also has a certain life cycle. Generally speaking, the AMOLED screen can be used for tens of thousands of hours.

Apple chief designer Jonathan Avi said in an interview that he believes that the iPhone needs to light up the entire screen panel every time. Therefore, when designing the Apple Watch, Ivey and his R&D team used as many black pixels as possible, and this more energy-efficient pixel can also effectively extend the battery life of the device.

But AMOLED also has its drawbacks.

(1) When the resolution is low, the graininess will be very heavy, and the edge of the text will be imaginary when the text is displayed.

(2) AMOLED emphasizes green (green is too bright), it is amazing at first glance, but it will be visually fatigued if you look at it for a long time.

(3) Because AMOLED is self-illuminating, there may be different degrees of aging of different pixels in the aging process, resulting in different brightness, so the color cast problem is more serious (and the LCD screen of the backlight is not worried).

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