OLED， Organic Light Emitting Diode, also known as Organic Electroluminescence Display (OELD).
Deng Qingyun, a Chinese American professor born in Hong Kong in 1947, discovered organic light-emitting diodes (OLEDs) in his laboratory and began research on OLEDs. In 1987, Deng Qingyun and Vanslyke used ultra-thin film technology, using transparent conductive film as the anode, AlQ3 as the light-emitting layer, triarylamine as the hole transport layer, and Mg/Ag alloy as the cathode, to create a double-layer organic electroluminescent device.
In 1990, Burroughes et al. discovered OLEDs using conjugated polymer PPV as the luminescent layer, which sparked a wave of OLED research worldwide. Professor Deng is also known as the "father of OLED" and has a huge international influence.
The luminous principle of OLED:
The light emission principle of OLED is similar to that of LED, which uses an external bias voltage to cause holes and electrons to start from the positive and negative electrodes respectively, and meet in the organic light-emitting layer to produce light emission. The anode is an ITO conductive film, and the cathode contains metals such as Mg, Al, Li, etc. Its basic structure is shown in Figure 4. The color of OLED light emission depends on the material of the organic light-emitting layer, so manufacturers can obtain the desired color by changing the material of the light-emitting layer. It can also be understood that the main principle of luminescence is the combination of electrons and holes to produce light. Depending on the material, the energy levels of electrons and holes also vary, resulting in different wavelengths (i.e. different colors) of light.
OLED can be divided into three types based on colorization: first, "RGB three color light-emitting structure", second, "color conversion structure [white light+color filter]", third, "color filter film [blue light+color conversion layer]", and so on. Due to the use of independent luminescent materials RGB (red, green, and blue) arranged in three colors for the 3-color luminescent structure, it has the characteristic of good luminous efficiency and does not require the addition of color filters or color conversion layers in thin films, which is currently being invested in
The most common usage method of manufacturers; However, due to the use of shadow mask evaporation in the 3-color process, the color accuracy is poor. The color transformation method uses blue luminescent materials to emit light, with a thin film in between, so the luminous efficiency is not as good as the 3-color luminescence method. Color filters use white light emitting materials to emit light, with a layer of color filter added in the middle, so the luminous efficiency is not as good as the 3-color luminous method. Currently, there are not many manufacturers with white light technology.
To illustrate the structure of OLED, each OLED unit can be compared to a hamburger, with the luminescent material being a vegetable sandwiched in the middle. Each OLED display unit can be controlled to produce three different colors of light. OLED, like LCD, also has active and passive types. The unit selected by the row and column address in passive mode is illuminated. In active mode, there is a thin film transistor (TFT) behind the OLED unit, and the light-emitting unit lights up under the driving of the TFT. Active OLED should be more energy-efficient and have better display performance than passive OLED.
