OLED, literally translated in Chinese as Organic Light Emitting Diode. It is the latest third-generation display technology after CRT and LCD display technology. The basic structure of the main OLED is composed of a power positive phase and a thin, transparent and semiconducting tin oxide (I below 0) connected to the power positive electrode, and is wrapped into a sandwich structure with another metal cathode. The entire structure layer includes the pore layer, the pore size transfer layer, the light-transmitting layer (organic material), the electron transport layer and the electron injection layer. When electricity is applied to the corresponding voltage, a positive hole charge, and the cathode is combined into a light-emitting layer, which generates three colors of red, green and blue light depending on the composition. OLED is a dual light injection device that uses a physical electroluminescence mechanism to directly convert electrical energy into light energy of organic semiconductor molecules. Unlike the traditional LCD mode, OLED does not require a backlight and has unique functions. It uses very thin coatings of organic materials and glass substrates, and when electric current is passed, these organic materials can emit light. The OLED display technology realizes color display in four ways: independent material luminescence method, color filter film method, color conversion method and micro-cavity toning method. The independent material light-emitting method directly uses independent red, green and blue organic light-emitting materials to provide the three primary colors, and the color filter film method converts white light into the red, green and blue primary colors required by color OLEDs through color filters. The color conversion method is mainly Using the blue with the highest energy of the three primary colors as the light source, the blue light is converted into red or green light with lower energy through the light color conversion film to provide the three primary colors. The micro-cavity toning method uses the micro-cavity effect to adjust the luminescence. The color becomes the three primary colors. In the market, Samsung's OLED uses RGB coloring separately, and LG's OLED TV uses a white light OLED+color filter display technology. Regarding the driving method of OLED, like LCD, its driving method is also divided into two types, active and passive. In the passive mode, it lights up according to the positioning, similar to the postman sending a letter. The active mode adds a thin film transistor on the back of each OLED unit like the TFT LCD, and the light-emitting unit lights up in accordance with the instructions received by the transistor. In short, the active/passive matrix method mainly refers to the electronic switch type that turns on or off the pixels in the display. A typical OLED consists of a cathode, an electron transport layer, a light-emitting layer, a hole transport layer and an anode. Electrons are injected from the cathode to the electron transport layer. Similarly, holes are injected from the anode into the hole transport layer, and they recombine in the light-emitting layer to emit photons. Unlike inorganic semiconductors, organic semiconductors (small molecules and polymers) have no energy band, so the charge carrier transport has no extended state. The energy state of the excited molecule is discontinuous, and the charge is transported mainly through the transition of carriers between molecules. Therefore, in organic semiconductors, the carrier mobility is several orders of magnitude lower than in inorganic semiconductors such as silicon, gallium arsenide, and even amorphous silicon. In actual OLEDs, the typical carrier mobility of organic semiconductors is 10-3~10-6cm2/V‧S. Because it is too small, the OLED device requires a higher operating voltage. For example, an OLED with a luminous intensity of 1000cd/m2, its working voltage is about 7~8V. For the same reason, OLED is limited by space charge, and its injected current density is higher. Pos Machine,Smart Android Pos,Smart Mobile Tablet Terminal,Smart Pos Z90 Guangzhou Winson Information Technology Co., Ltd. , https://www.winsonintelligent.com