Today, the failure of O LEDs is a problem. There are many problems involved in OLED failure. Although a lot of research has been done in the industry, the law of failure and the specific mechanism have not been fully revealed. Non-essential degradation factor In general, non-essential degradation is generally classified as long as it is not due to basic properties such as the structure and materials of the components. The most important manifestation of non-essential degradation is the increase in black spots. When the non-illuminated area is gradually increased, the area where the OLED emits light will be relatively reduced, which in turn affects the problem of life. Most of the materials used in OLED devices are extremely sensitive to moisture and oxygen. If the device is not packaged, it is easy to find many black non-light-emitting areas in its light-emitting area, and the black non-light-emitting area will be slower with time. Slower and bigger. The radius of the black region is roughly proportional to the quadratic root of time, which seems to imply that the formation of a black non-illuminated region is associated with a certain diffusion mechanism. Since the black non-light-emitting area is increased to a certain extent, we can see it with the naked eye, so the life of the OLED device is the earliest from the study of black spots. Essential deterioration Although the device can be effectively controlled due to the non-light-emitting region caused by external disturbances, it is found that the luminance of the device is degraded with time even if no black spots are generated. Obviously, this phenomenon is not caused by the outside world. It is the aging of the device, or the decline caused by the material itself. A very clear and perfect theory has not yet been formed to explain the current degradation of OLED devices, which also illustrates the complexity of the inherent degradation factors of OLED devices. Effect of water vapor oxygen on organic materials Many studies have shown that one of the factors affecting the life of organic EL devices is that the presence of water molecules and oxygen plays an important role in the action of organic EL materials, especially water molecules. However, how water molecules and oxygen change the organic layer, many articles at home and abroad have mentioned such problems, such as the oxidation of organic layers, but the specific process is unknown. Luminous area degradation After being sealed for a period of time, the packaged OLED device has a phenomenon that the light-emitting area is reduced or even not illuminated. It has been observed that the adhesive back cover of such a device and the epoxy resin of the glass front cover plated with the device material have voids. This means that the package is not tightly sealed and the air is in direct contact with the device. The reduction in the light-emitting area of ​​the device is likely to be related to such a bonding layer void. Oxygen and water vapor enter the device through the channel, affecting the performance of the device and changing the light-emitting area of ​​the device. The device was shot immediately after opening, because the device was only exposed to air for a few minutes after opening, so it can be seen that the light-emitting area is a relatively complete rectangle, the corners are sharp and angular, the brightness is uniform, and the three colors of red, green and blue alternate. After 30 minutes of power-on, the visible light-emitting area has been blurred from the four corners. The longer the time, the greater the change. The reduction in device area begins at the four corners of the device. This is because oxygen vapor intrudes into the interior of the device primarily through the edge of the device. Wet nitrogen environment The experiment ruled out the effects of oxygen and examined the effects of water vapor on the device. Obtain a humid nitrogen environment by: 1. Place the unsealed device in the system. 2. After connecting the wires, seal the other parts than the catheter 3. Completely close the system after continuous nitrogen flow for a period of time. 4, power on observation photo Failure device morphology analysis Observation of the device after failure revealed that the cathodes of the three color devices had different degrees of bubble-like protrusion structures. The color of the cathode at the edges and corners changes, and bubbles are randomly distributed inside the device. The area where the color of the cathode changes changes to a non-light-emitting area, and the bubble still emits light. In the SEM micrograph, it can be clearly seen that the cathode has different sizes of protrusions. A cross-sectional view of the bulge. Ac Motor,220V Servo Motor,Ac Motor With Speed Controller,Remote Motor With Speed Controller NingBo BeiLun HengFeng Electromotor Manufacture Co.,Ltd. , https://www.hengfengmotor.com
