OLED lighting must achieve the application level of fluorescent lamps in terms of efficiency, and its power efficiency must be at least 70lm / W. Although about 100lm / W OLED lighting devices have been reported, they are manufactured under very extreme conditions, usually Under the circumstances, the efficiency of the manufactured OLED lighting device is only 30 ~ 50lm / W, obviously this is far from meeting the requirements.
From the perspective of materials, to achieve such high efficiency, phosphorescent materials with luminous efficiency of up to 100% must be used. At present, green and red phosphorescent materials have no problems. What is urgently needed is blue phosphorescent materials that play an important role. . There is currently a lack of high-efficiency and high-stability blue phosphorescent luminescent materials, which is currently the main technical difficulty that hinders the improvement of the efficiency of OLED lighting devices. Therefore, the development of practical high-efficiency and high-stability blue-phosphorescent luminescent materials has become the The main research direction of the field.
From the perspective of device structure, effective device structure design is also the key to improving device efficiency. Current good device structures include multiple light-emitting layer structures, single light-emitting layer structures, stacked layer structures, and top-emission structures. The multi-light emitting layer structure is currently one of the most prepared white light OLED devices. The process is relatively mature and the device performance is also the best. However, the complex process may affect its future OLED lighting device yield and production cost issues, and this Structural devices sometimes have the disadvantage that the spectral and chromaticity coordinates vary with the driving voltage. However, due to the good device performance of the multiple light-emitting layer structure, and the problem that the spectrum and chromaticity coordinates change with the driving voltage can be completely solved by the design of the device structure, so if the yield can be controlled and improved, the structure is still It is a mass production technology, which is currently used by Philips, UDC and Novaled.
Although the single light-emitting structure can avoid the change of color purity with the driving voltage to a certain extent, it may also simplify the process during the production process, but the unsatisfactory efficiency and stability problems also make this structure unusable in practical applications. .
The stacked structure has the characteristics of a single light-emitting layer and multiple light-emitting layers. It is a device structure that connects multiple light-emitting units in series through a charge generation layer. The stacked device has very good spectral stability and high light emission. The characteristics of efficiency, high luminous brightness and good stability make the laminated structure device very competitive in practical applications. If the complex structure of the laminated structure can be further improved, the laminated structure device is expected to be used for lighting The mainstream technology of white light OLED production.
The top-emission structure may also become an important technological development direction for white OLEDs for lighting due to its advantages in effective light-emitting area and improved efficiency, and combining other structures with the top-emission structure can develop a white OLED with higher performance.
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