OLED (Organic Light Emitting Display) is an organic light-emitting display that is a new product on mobile phone LCDs and is known as a "dream display." Unlike traditional LCD displays, OLED display technology eliminates the need for backlights and uses very thin organic coatings and glass substrates that illuminate when current is passed through. And OLED displays can be made lighter and thinner, have a larger viewing angle, and can significantly save power.
At present, in the two major technical systems of OLED, low-molecular OLED technology is mastered in Japan, and the technology and patents of polymer PLED (the so-called OEL of LG mobile phone is the product of this system) are mastered by the British technology company CDT. There are still some difficulties in the colorization of PLED products. However, although OLEDs with better technology in the future may replace LCDs such as TFTs, organic light-emitting display technologies still have shortcomings such as short lifetime and large screen size.
The new generation of OLED display technology has overcome the problem of short life (more than 30,000 hours) and the difficulty of large screens (3.0 inches or more).
Unlike traditional LCD displays, OLED display technology eliminates the need for backlights and uses very thin organic coatings and glass substrates that illuminate when current is passed through. Moreover, the OLED display screen can be made lighter and thinner, has a larger viewing angle, and can significantly save power.
At present, in the two major technical systems of OLED, low-molecular OLED technology is mastered in Japan, and the so-called OEL of polymer PLEDLG mobile phone is this system. The technology and patents are mastered by British technology company CDT, compared with PLED products. There are still difficulties in colorization. Low-molecular-weight OLEDs are easier to colorize. Recently, Samsung released 65,530-color mobile phone OLEDs.
However, although OLEDs with better technology will replace LCDs such as TFTs in the future, organic light-emitting display technologies have shortcomings such as short lifetime and large screen size. At present, the main use of OLED is Samsung's new SCH-X339, which uses 256-color OLED. As for OEL, it is mainly used by LG in its CU8180 8280.
To illustrate the OLED configuration, each OLED unit can be compared to a hamburger, and the luminescent material is the vegetable sandwiched between them. The display unit of each OLED can be controlled to produce three different colors of light. Like LCDs, OLEDs are also active and passive. The unit selected by the row and column address in the passive mode is lit. In the active mode, there is a thin film transistor (TFT) behind the OLED unit, and the light emitting unit is lit under the TFT driving. Active OLEDs are more power efficient, but passive OLEDs offer better performance.
The basic structure of an OLED is composed of a thin, transparent semiconductor-indium tin oxide (ITO) connected to the positive electrode of the power, and another metal cathode, which is wrapped into a sandwich structure. The entire structural layer includes a hole transport layer (HTL), an illuminating layer (EL), and an electron transport layer (ETL). When the power is supplied to an appropriate voltage, the positive hole and the cathode charge are combined in the light-emitting layer to produce light, and the three primary colors of red, green and blue RGB are generated according to the formulation to form a basic color. The characteristics of OLEDs are self-illuminating. Unlike TFT LCDs, which require backlighting, they have high visibility and brightness, followed by low voltage requirements and high power saving efficiency, plus fast response, light weight, thin thickness, simple structure and low cost. Etc. is considered one of the most promising products of the 21st century.
The principle of illumination of organic light-emitting diodes is similar to that of inorganic light-emitting diodes. When the component is subjected to a forward bias derived from direct current (DC), the applied voltage energy drives the electrons (Electron) and the hole (Hole) from the cathode and the anode, respectively, when the two meet in conduction. In combination, a so-called Electro-Hole Capture is formed. When a chemical molecule is excited by external energy, if the electron spin (Electron Spin) and the ground state electron are paired, it is a singlet (Singlet), and the light released is so-called fluorescence (Fluorescence); The excited state electrons and the ground state electron spins are unpaired and parallel, which is called a triplet, and the light released is so-called Phosphorescence.
When the state of the electron is returned from the excited high energy level to the steady state low energy level, its energy will be emitted in the form of Light Emission or Heat Dissipation, respectively, wherein the photon portion can be utilized as a display function; However, the organic fluorescent material cannot observe the triplet phosphorescence at room temperature, so the theoretical limit of the luminous efficiency of the PM-OLED element is only 25%.
The principle of PM-OLED illumination is to use the material energy level difference to convert the released energy into photons, so we can choose the appropriate material as the luminescent layer or dope the luminescent layer to get the luminescent color we need. In addition, the general combination of electrons and holes is in the tens of nanoseconds (ns), so the response speed of the PM-OLED is very fast.
Typical structure of PM-OLEM. A typical PM-OLED is composed of a glass substrate, an indium tin oxide (ITO) anode, an organic light emitting layer (Emitting Material Layer), and a cathode (Cathode), among which a thin and transparent ITO anode. The organic light-emitting layer is sandwiched with the metal cathode as a sandwich, and when a hole injected with a voltage from the anode and an electron from the cathode are combined with the organic light-emitting layer, the organic material is excited to emit light.
In addition to the glass substrate, the yin and yang electrodes and the organic light-emitting layer, a hole injection layer (HIL) and a hole transport layer are required to be formed in the multilayer PM-OLED structure, which has a good luminous efficiency and is generally used. Hole Transport Layer; HTL), Electro Transport Layer (ETL) and Electron Inject Layer (EIL), and an insulating layer is required between each transport layer and the electrode, so Evaporate The processing difficulty is relatively increased and the production process is complicated.
Since organic materials and metals are quite sensitive to oxygen and moisture, they must be packaged and protected after fabrication. Although the PM-OLED needs to be composed of several layers of organic thin films, the thickness of the organic thin film layer is only about 1,000 to 1,500 A (0.10 to 0.15 um), and the total thickness of the entire display panel (Panel) is less than 200 μm after encapsulation plus desiccant. (2mm), with the advantage of thinness.