《WOLED-三线态激子的有效提取》-课件设计(公开).ppt

* * * * * * * * * * * * * * * * * * * content Introduction and the recent development Experiment * Results and discussion Conclusion Introduction and the recent development The multiple emission layers Example * * The tremendous developments of monochrome red, green and blue organic light-emitting diodes (OLEDs) since their first inception in 1987 have paved the way for the recent advancement of the white organic light-emitting diode (WOLED). The multiple emission layers architecture reported in the literature has been able to achieve the much desired saturated-white emission. The multiple emission layers * Shortcomings: a color-shift with an increase in current. Merits: carrier recombination, carrier trapping, and exciton diffusion, the emission of red, green, and blue portion can be tuned appropriately to obtain desired color purity. Solution Devices with a single emission layer doped with two or three dopants have been developed. To balance red, green and blue emissions, the concentration of each dopant is carefully controlled. * The blue-emitting phosphorescent molecule : unstable ; a relatively low operational lifetime. color degradation with time; the blue portion reduces significantly. The device with three-phosphorescent dopants also suffers a large efficiency roll-off. Sun et al.showed that by harvesting the singlet and triplets into two different channels, the efficiency roll-off can be improved. Sun et al. harvested the singlet (using fluorescent dye) near the exciton formation region and making use of the long diffusion length of triplet, harvested the triplet excitons at a distance from the formation region (using phosphorescent dyes). * Example The device reported in Ref. consists of doped and undoped regions where the excitons are harvested in the doped region. * The uniformity of the device for large-area fabrication. The small doping concentration and thin doped region, the excitons was not fully