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

摘要

Efficient orange-red phosphorescent organic light-emitting devices (PHOLED) with various doping concentrations of benzotriazole-iridium complex [(TBT)_2Ir(acac)] (bis[4-(2H-benzotriazol-2-yl)-N,N-diphenyl-aniline-N~1, C~3] iridium acetylacetonate) in 4,4'-N,N'-di(carbazolyI) 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. percent, the maximum external quantum efficiency (EQE), luminance and power yield reach 9.06 percent, 15.81 cd/A and 13.81m/W, respectively. Increasing the doping concentration from 5 percent to 30 wt. percent significantly decreases the driving voltage. The driving voltage of 30 percent (TBT)_2Ir(acac) doped device is only 3.16V at 1 mA/cm~2 with power yield of 13.321m/W.