We developed highly efficient fluorescent dopants for full‐color OLEDs. For blue, green and red OLEDs, current efficiencies of 8.7cd/A, 20.5 cd/A and 11.4 cd/A at 10mA/cm2 were achieved, respectively. Lifetime of the blue device was estimated to be 23,000hours at an initial luminance of 1,000 cd/m2. Moreover, long lifetime of 100,000 hours was estimated in the green and red devices. By the use of these dopants, we expect that a full‐color OLED display with the lifetime of 18,000 hours at a white luminance of 300 cd/m2 can be achieved.

We found a new device structure which has an efficiencyenhancement layer between emitting layer and electron transporting layer. We applied the structure to a pure blue fluorescent device with a CIE1931 coordinate of (0.14, 0.12) and successfully obtained very high EQE of over 10% with low driving voltage of 3.7 V at 10 mA/cm 2 and long lifetime of 10,000 hrs at an initial luminance of 1,000 cd/m 2 . Results of transient EL measurements indicated the contribution of triplet excitons to the high EQE.

The relationship between molecular shape of fluorescent blue dopants (BDs) IntroductionSome companies have started mass production of OLED TVs or OLED lighting. One of the most critical issues for OLED application is the reduction of power consumption due to the revision of power consumption regulation by "Energy Star" program or other commissions. Regarding phosphorescent devices, the performance of red or green devices has been dramatically improved and started to be used in practical applications. On the other hand, pure blue phosphorescent material with long lifetime has not yet been found. Therefore the improvement of fluorescent pure blue performance has been continuously needed. In 2008, we developed a technology to enhance the efficiency of blue fluorescence, "Triplet-triplet fusion (TTF)", however the efficiency was not so high under 10% of EQE [1].Recently molecular orientation attracts much attention to promote high efficiency of OLED. Specific molecular structures which show horizontal orientation to a substrate has been reported [2]. In addition, specific host and dopant materials show molecular orientation in a blue fluorescence device and show high EQE in doped and un-doped emitting systems [3][4][5].The objective of this paper is to reveal the relationship between molecular orientation property of applicative fluorescent blue dopants (BDs) and EQE of OLEDs. We composed four kinds of different fluorescent blue dopants with different molecular shape (ovality) and examined the influence of molecular orientation of BDs on the efficiency improvement of OLEDs. We found that BDs with larger ovality bring larger orientation factor and higher EQE in blue OLEDs with "Efficiency enhancement layer (EEL)" to enhance TTF phenomenon. Furthermore, as a result of analyzing IVL characteristic, impedance spectroscopy and transient EL [6][7][8], it was clarified that the effect of the EQE improvement depends only on the orientation of BD because they showed almost same carrier balance and TTF efficiency.

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Excellent organic electroluminescent materials are needed to obtain the color EL devices with high performance. We have succeeded in realizing bright and efficient devices with long lifetime in various color regions, based on styryl and amine derivatives.