Interpretation of OLED technology principles and its application products

The principle of OLED

OLED (Organic Light Emitting Display) refers to the phenomenon that organic semiconductor materials and luminescent materials emit light through carrier injection and recombination under the drive of an electric field. The principle is to use ITO transparent electrode and metal electrode as the anode and cathode of the device respectively. Under a certain voltage drive, electrons and holes are injected from the cathode and anode into the electron and hole transport layers respectively. Electrons and holes migrate to the luminescent layer through the electron and hole transport layers respectively, and meet in the luminescent layer to form excitons and excite the luminescent molecules, which emit visible light through radiation relaxation. The radiated light can be observed from the ITO side, and the metal electrode film also acts as a reflective layer. The display made according to this luminescence principle is called an organic light-emitting display, also called an OLED display.

Technical characteristics of OLED

Compared with LCD, OLED has a series of advantages, such as active light emission, no viewing angle problem, light weight, small thickness, high brightness, high luminous efficiency, rich luminous materials, easy to achieve color display, fast response speed, high dynamic picture quality, wide operating temperature range, flexible display, simple process, low cost, strong shock resistance, etc. Therefore, it is called the ideal display of the future by experts.

OLED product categories

There are several types of OLEDs - Passive Matrix OLED, Active Matrix OLED, Transparent OLED, Top Emitting OLED, Foldable OLED, White OLED, etc. Each type of OLED has its own unique uses. Next, we will discuss each of these types of OLEDs one by one.

First up are passive-matrix and active-matrix OLEDs.

Passive Matrix OLED (PMOLED)

PMOLED has a cathode strip, an organic layer, and an anode strip. The anode strip and the cathode strip are perpendicular to each other. The intersection of the cathode and the anode forms a pixel, which is the part that emits light. An external circuit applies current to the selected cathode and anode strips to determine which pixels emit light and which do not. In addition, the brightness of each pixel is proportional to the amount of current applied.

PMOLED is easy to manufacture, but it consumes more power than other types of OLED, mainly because it requires external circuitry. PMOLED is most efficient when used to display text and icons, and is suitable for small screens (2-3 inches diagonal), such as those often found on mobile phones, PDAs, and MP3 players. Even with an external circuit, passive-matrix OLEDs consume less power than the LCDs currently used in these devices.

Active Matrix OLED (AMOLED)

AMOLED has a complete cathode layer, organic molecule layer and anode layer, but the anode layer is covered with a thin film transistor (TFT) array to form a matrix. The TFT array itself is a circuit that determines which pixels emit light and thus determines the composition of the image.

AMOLED consumes less power than PMOLED because the TFT array requires less power than the external circuitry, making it suitable for large displays. AMOLED also has a higher refresh rate, making it suitable for displaying video. The best uses for AMOLED are computer monitors, large-screen TVs, and electronic signs or billboards.
Transparent OLED

Transparent OLEDs have only transparent components (substrate, anode, cathode) and can be up to 85% as transparent as the substrate when not emitting light. When a transparent OLED display is powered, light can pass through it in both directions. Transparent OLED displays can use either passive matrix or active matrix. This technology can be used to make head-up displays, which are often used on aircraft.

Top-emitting OLED

Top-emitting OLEDs have an opaque or reflective substrate. They are best suited for active-matrix designs. Manufacturers can use top-emitting OLED displays to make smart cards.

Foldable OLEDs

The base layer of foldable OLEDs is made of very flexible metal foil or plastic. Foldable OLEDs are very light and very durable. They can be used in devices such as mobile phones and PDAs to reduce device breakage, which is a major cause of returns and repairs. In the future, foldable OLEDs may be sewn into fabrics to make very "smart" clothing. For example, future wilderness survival suits can integrate computer chips, mobile phones, GPS receivers and OLED displays and sew them into the clothing.

White

OLEDs emit white light that is brighter, more even, and more energy efficient than fluorescent light. They also have the true color characteristics of incandescent lighting. OLEDs can be made into large-area thin sheets, so they can replace fluorescent lamps currently used in homes and buildings. In the future, the use of OLEDs is expected to reduce the energy consumption required for lighting.

OLED Product Outlook

1. OLED screen MP3, MP4

OLED display technology has been widely used in MP3 and MP4. In the design of the panel, a colorful backlight design has appeared. On this basis, further development has taken place, and some regions have begun to use color OLED panels.

2. OLED screen mobile phone

The use of OLED in mobile phone screens has been tried, but it has not yet reached the stage of widespread application. Samsung Panel Company has already used active OLED (AMOLED) screens in mobile phones. Many mobile phones with AMOLED displays have been sold on the market, with high display accuracy. For example, Lenovo LePhone uses AMOLED screens.

In the future, if a soft OLED screen can be made and the internal chip can be softened, mobile phones may be able to be rolled up at a small angle and will be even thinner.

3. OLED Tablets

OLED can be used in tablets to create ultra-thin, rollable products, or even completely transparent tablets. With built-in glass window navigation and real 3D interior design software, you can plan interior designs on a transparent screen and use a splitter to split the screen into two independent screens to share with others. Transparent technology and augmented reality applications will make traditional tablets more widely used.

4. OLED TV

Sony launched an 11-inch OLED TV in the Japanese market in December 2007. Some manufacturers, including Toshiba, Panasonic and many domestic brands, are also striving to enter this market. Especially at a time when the sales of LCD (including LED) liquid crystal TVs and PDP plasma TVs are slowing down in the market, OLED is likely to become the dominant force in the next generation of TVs.

OLED TVs are characterized by ultra-thinness, wide viewing angles, and even "soft" TVs with foldable and bendable displays. They can be hung on the wall or put in a pocket like a piece of paper. It is rumored that Apple is also planning to equip Apple TV with a 55-inch LG OLED display.