Phosphorescent OLEDs, white

The record-efficiency of OLEDs is based on small molecules. Their characteristics are often unpublished and protected by patents. Novaled reports on 16% and 19% external quantum efficiencies for red and green phosphorescent OLED, respectively, whereas Universal Display produced a 20% white OLED. 

Another example of a white phosphorescent OLED with triple-doped EML was demonstrated recently. The device architecture was similar to that described above however, the material structures used were not disclosed. At lOOOcd/m the white triplet OLED showed 251m/W, CRI index of 78, and CIEx,y of (0.39,0.44). At lOOcd/m, the device power efficacy reached 301m/W, and with outcoupling enhancement the total power efficacy increased to 511m/W. 

Nakayama et al. reported highly efficient and stable single-stack white phosphorescent OLEDs based on blue triplet emitter KMBD-342 described in Section 14.4.2.3. Yellow-green (YD-85) and red (RD-61) dopants used in the device were provided by Universal Display Corporation. The device layer structure was as follows Light outcoupling film ITO HIL HTL green EML red EML I blue EML HBL n-doped ETL A1. At 1000cd/m the performance... 

Schematic of white phosphorescent OLED device with six organic materials. (Reproduced from D Andrade, B. et at, SID Inti. Symp. Dig. Tech. Papers, 39, 940,2008. With permission.)...

Sun, Y., Giebink, N. C., Kanno, H. et al. 2006. Management of singlet and triplet excitons for efficient white organic light-emitting devices. Nature 440 908. Deaton, J. C., Kondakova, M. E., Kondakov, D. Y. et al. 2007. Triplet exciton diffusion in hybrid fluorescent/phosphorescent OLEDs. SID Inti. Symp. Dig. Tech. Papers 38 849. 

In the vapor-deposited OLED community, a number of approaches have been employed to produce white light emission. White OLEDs have been demonstrated based on multilayer structures, e.g., stacked backlights [153,168], multidoping of single-layer structures [145], phosphorescent monomer-excimer emission layers [169] and on doping of phosphorescent materials into separate bands within the emission zone, called a tri-junction [170]. The trijunction device has produced the highest white OLED efficiency of 16% external quantum efficiency demonstrated thus far [171]. 

Y Tung, T Ngo, M Hack, J Brown, N Koide, Y Nagara, Y Kato, and H Ito, High Efficiency Phosphorescent White OLED for LCD Backlight and Display Applications, Proceedings of the Society for Information Display, Digest of Technical Papers, Vol. 35, Seattle, 2004, pp. 48-51. 

White OLED Devices Based on Phosphorescent Emitters...491... 

Single-Stack White OLED Devices Incorporating Phosphorescent Emitters... 

Device architectures of white OLEDs using phosphorescent emitters can be similar to the architectures described in Section 14.3.5. The white color can be generated by the simultaneous emission of light from multiple emitters in... 

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