Organic Light-EmitTIng Diode (OLED) has no backlight, high contrast, thin thickness, wide viewing angle, fast response, flexible panel, and wide temperature range. The excellent characteristics of structure, process and process are considered to be the next generation of flat panel display emerging application technologies. Therefore, many manufacturers around the world are investing in research and development. According to the understanding and estimation, China's current mobile phone market adopts OLED products. The model [monochrome OLED10, regional color 15 models, 256 colors 8 models, full color 3 models] (see Table 1), according to the knowledge that the domestic mobile phone design company is currently developing OLED mobile phones, there are 7 models. Together with SKD/CKD products and international branded products.
It is expected that by the end of the year, there will be 50 OLED mobile phones in China's mobile phone market, which is popular in China's mobile phone market (see Table 2). At the same time, the data in the comprehensive table 3 shows that OLED is expected to compete with STN-LCD and TFT-LCD technology in the future. So far, we will introduce the knowledge of OLED.
According to the material classification, it can be roughly divided into two types: small molecule system and polymer type. The small molecule system is made of dye and pigment, called OLED. In 1987, it was made by Eastman Kodak Co. of the United States. CWTang [Dr. Deng Qingyun, born in Hong Kong, graduated from the Department of Chemistry, National Taiwan University] published, the polymer system is based on conjugated polymer, called PLED (Polymer Light-emitTIng Diode) or LEP (Light-emitTIng Polymer Device) was proposed by the University of Cambridge (Cambrige Univ.) in 1990. In 1992, Cambridge established the display technology company CDT (Cambrige Display Technology) to commercialize PLED.
Second, the principle of OLED lightThe principle of OLED illumination is similar to that of LED. The external bias is used to make the hole and the electron respectively start from the positive and negative electrodes, and the organic light-emitting layer meets to produce the light-emitting effect. The anode is ITO conductive film, and the cathode contains Mg, Al, The basic structure of a metal such as Li is shown in Fig. 4. The color of the OLED light emission depends on the material of the organic light-emitting layer, so the manufacturer can change the material of the light-emitting layer to obtain the desired color. It can also be understood that the main principle of illuminating is that light is combined with electrons to generate light. Depending on the material, the energy levels of electrons and holes are also different, and light of different wavelengths (ie, different colors) is generated.
Third, OLED / Polymer OLED (polymer OLED)
OLED is a self-luminous material, which does not require a backlight board. At the same time, the viewing angle is wide, the image quality is uniform, the reaction speed is fast, the color is easy to be colorized, and the simple driving circuit can achieve illumination, simple process, and can be made into a flexible panel. In accordance with the principle of lightness and thinness, the application range is small and medium-sized panels; however, due to the high driving voltage of the OLED, the efficiency of use in energy is poor. Because PLED does not need to go through the thin film process and high-priced vacuum device, the component structure is only 2 layers, which is relatively simple, so the investment cost is much lower than that of OLED; but because PLED is not as good in color performance as OLED, each color decay constant Different, the color deviation must be compensated, and the bandwidth is large, and the color of the light is not easy to adjust. Therefore, the life of the product is also relatively short. At present, the main application range of the PLED is mainly a large-sized panel. From the perspective of market segmentation of products, the market niche of OLEDs is going to develop products with high unit price and high added value, while PLED is developing for a large number of low-priced products.
Fourth, passive OLED and active OLED
OLEDs can be divided into passive driving (PM MOS) and active driving (AcTIve Matrix; AMOLED) by driving mode. The driving mode of OLED is current driving. The structure of the passive mode is simpler, and the driving current determines the gray scale. The resolution and image quality applied to the small-sized products are not bad. However, if you want to develop the large-size application products, you may increase the power consumption and life. Reduced problems occur. The best corresponding is to use the active drive method, because the active current rectification is better than the passive method, it is not easy to generate leakage, and when used in low-temperature polysilicon (Poly-si) TFT technology, the current can produce impedance. Low-profile TFTs meet the needs of large-size, large-screen OLED displays.
OLEDs can be divided into three types by colorization, one, "RGB three-color light-emitting structure", two, "color conversion structure [white light + color filter]", three, "color filter film [blue light + color Conversion layer]" and other three ways. Since the three-color light-emitting structure is arranged by using three colors of independent light-emitting materials RGB (red, green and blue), it has the characteristics of good light-emitting efficiency, and it is not necessary to add a color filter or a color conversion layer film, which is the most common for current manufacturers. The method of use; however, since the 3-color process is a shadow mask evaporation method, the fineness of the color is poor. The color conversion method is to emit light with a blue luminescent material, and a thin film is interposed at the time of illuminating, so the luminous efficiency is not as good as the three-color illuminating method. The color filter is illuminated by a white light-emitting material, and a color filter is added in the middle. Therefore, the luminous efficiency is not as good as that of the 3-color light-emitting method. Currently, there are not many manufacturers with white light technology.
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