OLED (Organic Light Emitting Display) is an organic light-emitting display, which is a new product on mobile phone LCD and is known as "dream display". OLED display technology differs from traditional LCD display methods in that it does not require a backlight, uses a very thin coating of organic materials and a glass substrate, and when an electric current passes, these organic materials emit light. And OLED displays can be made lighter and thinner, with larger viewing angles, and can significantly save power consumption.
At present, in the two major technical systems of OLED, low-molecular OLED technology is mastered by Japan, and the technology and patents of polymer PLED (LG mobile phone so-called OEL is the product of this system) are mastered by the British technology company CDT, and the two are still difficult to color PLED products. However, although OLEDs with better technology may replace LCDs such as TFT in the future, organic light-emitting display technology still has shortcomings such as short service life and difficulty in large-scale screens.
The new generation of OLED display technology has overcome the problems of short service life (more than 3,3 hours) and large-scale screens (more than 0.<> inches).
OLED display technology differs from traditional LCD display methods in that it does not require a backlight, uses a very thin coating of organic materials and a glass substrate, and when an electric current passes, these organic materials emit light. Moreover, OLED display screens can be made lighter and thinner, with larger viewing angles, and can significantly save power.
At present, in the two major technical systems of OLED, low-molecular OLED technology is mastered by Japan, and the so-called OEL of polymer PLEDLG mobile phone is this system, and the technology and patents are mastered by the British technology company CDT, and the two are still difficult to color PLED products. Low-molecular OLEDs are easier to color, and not long ago Samsung released 65530 colors of OLED for mobile phones.
However, although OLEDs with better technology will replace LCDs such as TFT in the future, organic light-emitting display technology still has shortcomings such as short service life and difficulty in large-scale screens. At present, the use of OLED is mainly Samsung, such as the newly listed SCH-X339 uses 256 color OLED, as for OEL is mainly used by LG, on its CU8180, 8280 we have seen.
In order to illustrate the structure of the OLED, each OLED unit can be compared to a hamburger, and the luminous material is the vegetable sandwiched in the middle. Each OLED display unit can controllably produce three different colors of light. OLED, like LCD, is also active and passive. In passive mode, the unit selected by the row and column address is lit. In active mode, there is a thin-film transistor (TFT) behind the OLED unit, and the light-emitting unit lights up under the TFT drive. Active OLED is more power-efficient, but passive OLED displays better performance.
The basic structure of OLED is a thin, transparent indium tin oxide (ITO) with semiconductor characteristics, connected to the positive electrode of electricity, and another metal cathode, wrapped in a sandwich-like structure. The entire structural layer includes: hole transport layer (HTL), light-emitting layer (EL) and electron transport layer (ETL). When the power supply is to the appropriate voltage, the positive hole and the cathode charge will combine in the light-emitting layer to produce light, and the three primary colors of red, green and blue RGB will be produced according to their formulas, constituting the basic color. OLED is characterized by its own light, unlike TFT LCD that requires backlight, so the visibility and brightness are high, followed by low voltage demand and high power-saving efficiency, coupled with fast response, light weight, thin thickness, simple structure, low cost, etc., it is regarded as one of the most promising products in the 21st century.
The luminescence principle of organic light-emitting diodes is similar to that of inorganic light-emitting diodes. When the component is subjected to the forward bias derived from direct current (DC), the voltage energy will drive electrons and holes from the cathode and anode into the element, respectively, when the two meet and combine in conduction, that is, the so-called electron-hole capture (Electron-hole capture). When the chemical molecule is excited by foreign energy, if the electron spin (Electron Spin) and the ground state electron are paired, it is a singlet state, and the light released by it is the so-called fluorescence; Conversely, if the spins of excited electrons and ground electrons are not paired and parallel, they are called triplets, and the light they emit is called phosphorescence.
When the state position of the electron returns from the excited high energy level to the steady-state low energy level, its energy will be released in the form of light emission or heat dissipation, respectively, in which the photon part can be used as a display function; However, organic fluorescent materials cannot observe triple phosphorescence at room temperature, so the theoretical limit value of luminous efficiency of PM-OLED components is only 25%.
The principle of PM-OLED luminescence is to use the energy difference of the material to convert the released energy into photons, so we can choose the appropriate material as a light-emitting layer or doping dyes in the light-emitting layer to get the luminescent color we need. In addition, the binding reaction between electrons and holes is within tens of nanoseconds (ns), so the response speed of PM-OLED is very fast.
Typical structure of PM-OLEM. A typical PM-OLED consists of a glass substrate, ITO (indium tin oxide; Indium tin oxide) anode (Anode), organic light-emitting material layer (Emitting Material Layer) and cathode (Cathode), etc., in which the thin and transparent ITO anode and the metal cathode are sandwiched in the organic light-emitting layer like a sandwich, and when the voltage is injected into the hole of the anode and the electron from the cathode (Electron) is combined in the organic light-emitting layer, the organic material is excited to emit light.
At present, the multi-layer PM-OLED structure with better luminous efficiency and commonly used, in addition to the glass substrate, cathode and anode electrode and organic light-emitting layer, it is necessary to make a hole injection layer (Hole Inject Layer; HIL), Hole Transport Layer; HTL), Electron Transport Layer (Electron Transport Layer; ETL) and Electron Inject Layer; EIL) and other structures, and an insulating layer needs to be provided between each transport layer and the electrode, so the difficulty of Evaporate processing is relatively high, and the production process becomes complicated.
Since organic materials and metals are quite sensitive to oxygen and water vapor, they need to be encapsulated and protected after production. Although PM-OLED needs to be composed of several layers of organic film, the thickness of the organic film layer is only about 1,000~1,500A° (0.10~0.15 um), and the total thickness of the entire display board (Panel) is less than 200um (2mm) after adding desiccant (Desiccant), which has the advantage of being light and thin.