Small molecule host system for solution-processed red phosphorescent OLEDs

We demonstrate high efficiency solution-processed red phosphorescent OLEDs with small molecule mixed host systems. 2-TNATA (4,4',4 ''-tris(N-(2-naphthyl)-N-phenyl-amino)triphenylamine):TPBI (2,2',2 ''-(1,3,5-phenylene)tris(1-phenyl-1H-benzimidazole)) and m-MTDATA (4,4',4 ''-tri-(N-3-methylphenyl-N-phenylamino)triphenylamine):TPBI host systems are reported as good soluble mixed host systems. A doping level of 3% bis(2-phenylquinoline)(acetylacetonate)iridium (Ir(phq)(2)acac) dopant in the 2-TNATA:TPBI (1:1 ratio) mixed host produces the best quantum efficiency and driving voltage. This fabricated red phosphorescent OLED has a driving voltage of 5.2V and maximum current and power efficiencies of 17.8 cd/A and 11.3 lm/W, respectively. Minimal electron or hole trapping in the phosphorescent dopant molecules and prevention of self quenching by the low doping technique appear to be the key reasons for good device performance. Crown Copyright (C) 2010 Published by Elsevier B.V. All rights reserved.