OLED high light efficiency needs to solve material and structural problems

OLED lighting should reach the application level of fluorescent lamps in efficiency, and its power efficiency should be at least 70lm/W. Although OLED lighting devices of about 100lm/W have been reported so far, this is manufactured under very extreme conditions, usually The efficiency of the OLED lighting device manufactured in the case is only 30~50lm/W, which is obviously far from the requirement.

From the material point of view, in order to achieve such high efficiency, it is necessary to use a phosphorescent material with a luminous efficiency of up to 100%. At present, green and red phosphorescent materials have no problem, and an urgent need to solve is a blue phosphorescent material that plays an important role. . Nowadays, there is a lack of high-efficiency and high-stability blue-light phosphorescent materials, which is also the main technical difficulty that hinders the efficiency improvement of OLED lighting devices. Therefore, it has become a mass production technology to develop practical high-efficiency and high-stability blue phosphorescent materials. The main research direction of the field.

From the perspective of device structure, effective device structure design is also the key to improve device efficiency. Currently, a good device structure includes a multi-emission layer structure, a single luminescent layer structure, a stacked structure, and a top emission structure. The multi-emissive layer structure is one of the most widely used white OLED devices. The process is relatively mature and the device performance is the best, but the complicated process may affect its yield and production cost of OLED lighting devices in the future. Structural devices sometimes have the disadvantage that the spectral and chromaticity coordinates vary with the drive voltage. However, the multi-emissive layer structure due to good device performance, and the problem of spectral and chromaticity coordinates changing with the driving voltage can be completely solved by the design of the device structure, so if it can be controlled and improved in yield, the structure is still It is a mass production technology, which is currently used by Philips, UDC, and Novaled.

Although the single-emitting structure can avoid the change of color purity with the driving voltage to some extent, it may also simplify the process in the production process, but the unsatisfactory efficiency and stability problems also make this structure not applicable in practical applications. .

The laminated structure has the characteristics of a single light-emitting layer and a multi-light-emitting layer structure, and is a device structure in which a plurality of light-emitting units are connected in series through a charge generating layer, and the laminated device has excellent spectral stability and high light-emitting. The characteristics of high efficiency, high brightness and good stability make the laminated structure device very competitive in practical applications. If the process of complex 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 technical development direction of white OLED for illumination due to its advantages in effective light-emitting area and improved efficiency, and the combination of other structures and top emission structures can develop a higher performance white light OLED.