Organic light-emitting diode (OLED) refers to the phenomenon that organic semiconductor materials and light-emitting materials are driven by an electric field to cause light emission through carrier injection and recombination. The principle is to use indium tin oxide (ITO) transparent electrodes and metal electrodes as the anode and cathode of the device, respectively. Driven by a certain voltage, electrons and holes respectively migrate through the transport layer to the light-emitting layer, and meet in the light-emitting layer to form excitons and excite the light-emitting molecules, so that the light-emitting molecules emit visible light through radiation. OLED is an all solid-state thin-film light-emitting device, which is made of organic materials and amorphous materials, and has the advantages of wide field of view, ultra-thin, fast response, and high luminous efficiency. The transport layer used in OLED is made by doping with organic conjugated molecular materials. Because organic conjugated molecular materials have semiconductor characteristics in an undoped state, and they are simple to prepare, process large-area thin-film devices with simple technology, and low cost, the application of OLEDs is more extensive.
Figure 1. Organic Light-Emitting Diode (OLED) material structure
- Displays: OLED displays have a wide range of applications, such as mobile phone displays, computer displays, car displays, digital cameras, and other fields. OLED display is a self-luminous display technology and does not require any backlight at all. Compared with liquid crystal displays (LCD), OLED has the advantages of short response time, full color, self-luminescence, wide viewing angle, low voltage, low temperature operation, and flexible display.
- Lighting: OLED lighting belongs to solid state lighting, which has the advantages of low heat generation, low power consumption, fast response speed, small size, shock resistance and impact resistance, and easy development of light, thin and short products. OLED can be combined with different light colors to form various modules with soft illuminance. It also has the characteristics of light and thin, flat panel lighting, etc., and can be used for some special lighting designs, such as car lights, light strips, and flat panel lights.
- Driver: OLED drivers have the advantages of high working efficiency, high picture contrast, wide viewing angle, low working voltage, and simplicity in manufacturing. OLED driving can be divided into active driving and passive driving. Both driving methods have their own advantages and disadvantages. The driving method needs to be selected according to the size of the output current to the driver, the refresh frequency, and the material of the substrate.
- Bernard Geffroy, Philippe le Roy, Christophe Prat. Organic light-emitting diode (OLED) technology: materials, devices and display technologies [J].Polymer International., 2006, 6(55),572-582.