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2 February 2001 Optimization of driving lifetime durability in organic LED devices using Ir complex
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Multilayer organic light-emitting device with phosphorescent guest emitter, tris(2-phenylpyridine)iridium [Ir(ppy)3] doped in a host 4,4'-N,N'-dicarbazol-biphenyl (CBP) layer, exhibited very high luminous efficiency. A device having such phosphorescent guest emitter could not offer sufficiently long driving lifetime required by real products. On the other hand, phosphorescence in organic molecules rarely occurs at room temperature. We studied ways to increase driving lifetime by three types of experiments. First, we investigated to see whether the driving lifetime is dependent on guest molecule concentration. Second, we inserted Copper phtalocyanine (CuPc) between Indium Tin Oxide (ITO) anode and hole transport layer, 4,4'-bis[N- (naphthyl)-N-phenyl-amino]biphenyl (NPB) to prevent driving voltage from rising during constant current operation. Finally, we exchanged the hole blocking layer, which is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), for [(1,1'-biphenyl)-4-olato]bis(2-methyl-8- quinolinolato N1,08)aluminum (BAlq). Optimizing all of the above mentioned steps, we can expect the half decay lifetime of 20000 hours or over at an initial luminance of 100 cd/m2 by constant current driving.
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Teruichi Watanabe, Kenji Nakamura, Shin Kawami, Yoshinori Fukuda, Taishi Tsuji, Takeo Wakimoto, and Satoshi Miyaguchi "Optimization of driving lifetime durability in organic LED devices using Ir complex", Proc. SPIE 4105, Organic Light-Emitting Materials and Devices IV, (2 February 2001);

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