Low driving voltage and efficient orange-red phosphorescent organic light-emitting devices based on a benzotriazole iridium complex

Abstract

Efficient orange-red phosphorescent organic light-emitting devices (PHOLED) with various doping concentrations of benzotriazole-iridium complex [(TBT)(2)Ir(acac)] (bis[4-(2H-benzotriazol-2-yl)-N,N-wdiphenyl-aniline-N(1),C(3)] iridium acetylacetonate) in 4,4'-N,N'-di(carbazolyl) biphenyl (CBP) host were fabricated. The sterically hindered iridium ligands alleviate self-quenching of the phosphorescence at high doping levels. Under the optimal doping concentration of 20 wt.%, the maximum external quantum efficiency (EQE), luminance and power yield reach 9.06%, 15.81 cd/A and 13.8 Im/W, respectively. Increasing the doping concentration from 5% to 30 wt.% significantly decreases the driving voltage. The driving voltage of 30% (TBT)(2)Ir(acac) doped device is only 3.16V at 1 mA/cm(2) with power yield of 13.32 lm/W. (C) 2009 Elsevier B.V. All rights reserved.